From eab5ff4eaeaf39ed36eb770ba235a670e051db5a Mon Sep 17 00:00:00 2001
From: Dmitry Gozman <dgozman@gmail.com>
Date: Thu, 20 Aug 2020 11:25:33 -0700
Subject: [PATCH] chore(rpc): use channels types in dispatchers (#3549)

This ensures we actually implement channels as intended.
For example, this change found an issue with Route.fulfill.
---
 src/network.ts                             |  9 ++-
 src/rpc/server/browserDispatcher.ts        | 14 ++--
 src/rpc/server/browserTypeDispatcher.ts    |  8 +--
 src/rpc/server/cdpSessionDispatcher.ts     |  6 +-
 src/rpc/server/consoleMessageDispatcher.ts |  4 +-
 src/rpc/server/dialogDispatcher.ts         |  4 +-
 src/rpc/server/dispatcher.ts               |  4 +-
 src/rpc/server/downloadDispatcher.ts       | 12 ++--
 src/rpc/server/electronDispatcher.ts       | 16 ++---
 src/rpc/server/elementHandlerDispatcher.ts | 61 +++++++++--------
 src/rpc/server/frameDispatcher.ts          | 66 +++++++++----------
 src/rpc/server/jsHandleDispatcher.ts       | 21 +++---
 src/rpc/server/networkDispatchers.ts       | 21 +++---
 src/rpc/server/pageDispatcher.ts           | 77 +++++++++++-----------
 src/rpc/server/playwrightDispatcher.ts     |  4 +-
 src/rpc/server/selectorsDispatcher.ts      | 10 +--
 src/rpc/server/streamDispatcher.ts         |  6 +-
 17 files changed, 173 insertions(+), 170 deletions(-)

diff --git a/src/network.ts b/src/network.ts
index c47fa5ae16..93448aac39 100644
--- a/src/network.ts
+++ b/src/network.ts
@@ -190,10 +190,15 @@ export class Route {
     await this._delegate.abort(errorCode);
   }
 
-  async fulfill(response: types.NormalizedFulfillResponse) {
+  async fulfill(response: { status?: number, headers?: types.HeadersArray, body?: string, isBase64?: boolean }) {
     assert(!this._handled, 'Route is already handled!');
     this._handled = true;
-    await this._delegate.fulfill(response);
+    await this._delegate.fulfill({
+      status: response.status === undefined ? 200 : response.status,
+      headers: response.headers || [],
+      body: response.body || '',
+      isBase64: response.isBase64 || false,
+    });
   }
 
   async continue(overrides: types.NormalizedContinueOverrides = {}) {
diff --git a/src/rpc/server/browserDispatcher.ts b/src/rpc/server/browserDispatcher.ts
index 1c045b1092..1f686e3d85 100644
--- a/src/rpc/server/browserDispatcher.ts
+++ b/src/rpc/server/browserDispatcher.ts
@@ -16,14 +16,14 @@
 
 import { Browser } from '../../browser';
 import { Events } from '../../events';
-import { BrowserChannel, BrowserContextChannel, BrowserInitializer, CDPSessionChannel, Binary, BrowserNewContextParams } from '../channels';
+import * as channels from '../channels';
 import { BrowserContextDispatcher } from './browserContextDispatcher';
 import { CDPSessionDispatcher } from './cdpSessionDispatcher';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import { CRBrowser } from '../../chromium/crBrowser';
 import { PageDispatcher } from './pageDispatcher';
 
-export class BrowserDispatcher extends Dispatcher<Browser, BrowserInitializer> implements BrowserChannel {
+export class BrowserDispatcher extends Dispatcher<Browser, channels.BrowserInitializer> implements channels.BrowserChannel {
   constructor(scope: DispatcherScope, browser: Browser, guid?: string) {
     super(scope, browser, 'Browser', { version: browser.version() }, true, guid);
     browser.on(Events.Browser.Disconnected, () => this._didClose());
@@ -34,7 +34,7 @@ export class BrowserDispatcher extends Dispatcher<Browser, BrowserInitializer> i
     this._dispose();
   }
 
-  async newContext(params: BrowserNewContextParams): Promise<{ context: BrowserContextChannel }> {
+  async newContext(params: channels.BrowserNewContextParams): Promise<channels.BrowserNewContextResult> {
     return { context: new BrowserContextDispatcher(this._scope, await this._object.newContext(params)) };
   }
 
@@ -42,17 +42,17 @@ export class BrowserDispatcher extends Dispatcher<Browser, BrowserInitializer> i
     await this._object.close();
   }
 
-  async crNewBrowserCDPSession(): Promise<{ session: CDPSessionChannel }> {
+  async crNewBrowserCDPSession(): Promise<channels.BrowserCrNewBrowserCDPSessionResult> {
     const crBrowser = this._object as CRBrowser;
     return { session: new CDPSessionDispatcher(this._scope, await crBrowser.newBrowserCDPSession()) };
   }
 
-  async crStartTracing(params: { page?: PageDispatcher, path?: string, screenshots?: boolean, categories?: string[] }): Promise<void> {
+  async crStartTracing(params: channels.BrowserCrStartTracingParams): Promise<void> {
     const crBrowser = this._object as CRBrowser;
-    await crBrowser.startTracing(params.page ? params.page._object : undefined, params);
+    await crBrowser.startTracing(params.page ? (params.page as PageDispatcher)._object : undefined, params);
   }
 
-  async crStopTracing(): Promise<{ binary: Binary }> {
+  async crStopTracing(): Promise<channels.BrowserCrStopTracingResult> {
     const crBrowser = this._object as CRBrowser;
     const buffer = await crBrowser.stopTracing();
     return { binary: buffer.toString('base64') };
diff --git a/src/rpc/server/browserTypeDispatcher.ts b/src/rpc/server/browserTypeDispatcher.ts
index 7a9fd61eaa..1286400fb4 100644
--- a/src/rpc/server/browserTypeDispatcher.ts
+++ b/src/rpc/server/browserTypeDispatcher.ts
@@ -16,11 +16,11 @@
 
 import { BrowserTypeBase, BrowserType } from '../../server/browserType';
 import { BrowserDispatcher } from './browserDispatcher';
-import { BrowserChannel, BrowserTypeChannel, BrowserContextChannel, BrowserTypeInitializer, BrowserTypeLaunchParams, BrowserTypeLaunchPersistentContextParams } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import { BrowserContextDispatcher } from './browserContextDispatcher';
 
-export class BrowserTypeDispatcher extends Dispatcher<BrowserType, BrowserTypeInitializer> implements BrowserTypeChannel {
+export class BrowserTypeDispatcher extends Dispatcher<BrowserType, channels.BrowserTypeInitializer> implements channels.BrowserTypeChannel {
   constructor(scope: DispatcherScope, browserType: BrowserTypeBase) {
     super(scope, browserType, 'BrowserType', {
       executablePath: browserType.executablePath(),
@@ -28,12 +28,12 @@ export class BrowserTypeDispatcher extends Dispatcher<BrowserType, BrowserTypeIn
     }, true);
   }
 
-  async launch(params: BrowserTypeLaunchParams): Promise<{ browser: BrowserChannel }> {
+  async launch(params: channels.BrowserTypeLaunchParams): Promise<channels.BrowserTypeLaunchResult> {
     const browser = await this._object.launch(params);
     return { browser: new BrowserDispatcher(this._scope, browser) };
   }
 
-  async launchPersistentContext(params: BrowserTypeLaunchPersistentContextParams): Promise<{ context: BrowserContextChannel }> {
+  async launchPersistentContext(params: channels.BrowserTypeLaunchPersistentContextParams): Promise<channels.BrowserTypeLaunchPersistentContextResult> {
     const browserContext = await this._object.launchPersistentContext(params.userDataDir, params);
     return { context: new BrowserContextDispatcher(this._scope, browserContext) };
   }
diff --git a/src/rpc/server/cdpSessionDispatcher.ts b/src/rpc/server/cdpSessionDispatcher.ts
index a1f585d82d..0b9414c4e2 100644
--- a/src/rpc/server/cdpSessionDispatcher.ts
+++ b/src/rpc/server/cdpSessionDispatcher.ts
@@ -15,10 +15,10 @@
  */
 
 import { CRSession, CRSessionEvents } from '../../chromium/crConnection';
-import { CDPSessionChannel, CDPSessionInitializer } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 
-export class CDPSessionDispatcher extends Dispatcher<CRSession, CDPSessionInitializer> implements CDPSessionChannel {
+export class CDPSessionDispatcher extends Dispatcher<CRSession, channels.CDPSessionInitializer> implements channels.CDPSessionChannel {
   constructor(scope: DispatcherScope, crSession: CRSession) {
     super(scope, crSession, 'CDPSession', {}, true);
     crSession._eventListener = (method, params) => {
@@ -27,7 +27,7 @@ export class CDPSessionDispatcher extends Dispatcher<CRSession, CDPSessionInitia
     crSession.on(CRSessionEvents.Disconnected, () => this._dispose());
   }
 
-  async send(params: { method: string, params?: any }): Promise<{ result: any }> {
+  async send(params: channels.CDPSessionSendParams): Promise<channels.CDPSessionSendResult> {
     return { result: await this._object.send(params.method as any, params.params) };
   }
 
diff --git a/src/rpc/server/consoleMessageDispatcher.ts b/src/rpc/server/consoleMessageDispatcher.ts
index 7051ae10f7..5ff601d636 100644
--- a/src/rpc/server/consoleMessageDispatcher.ts
+++ b/src/rpc/server/consoleMessageDispatcher.ts
@@ -15,11 +15,11 @@
  */
 
 import { ConsoleMessage } from '../../console';
-import { ConsoleMessageChannel, ConsoleMessageInitializer } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import { createHandle } from './elementHandlerDispatcher';
 
-export class ConsoleMessageDispatcher extends Dispatcher<ConsoleMessage, ConsoleMessageInitializer> implements ConsoleMessageChannel {
+export class ConsoleMessageDispatcher extends Dispatcher<ConsoleMessage, channels.ConsoleMessageInitializer> implements channels.ConsoleMessageChannel {
   constructor(scope: DispatcherScope, message: ConsoleMessage) {
     super(scope, message, 'ConsoleMessage', {
       type: message.type(),
diff --git a/src/rpc/server/dialogDispatcher.ts b/src/rpc/server/dialogDispatcher.ts
index 202466ffdc..55b678efaf 100644
--- a/src/rpc/server/dialogDispatcher.ts
+++ b/src/rpc/server/dialogDispatcher.ts
@@ -15,10 +15,10 @@
  */
 
 import { Dialog } from '../../dialog';
-import { DialogChannel, DialogInitializer } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 
-export class DialogDispatcher extends Dispatcher<Dialog, DialogInitializer> implements DialogChannel {
+export class DialogDispatcher extends Dispatcher<Dialog, channels.DialogInitializer> implements channels.DialogChannel {
   constructor(scope: DispatcherScope, dialog: Dialog) {
     super(scope, dialog, 'Dialog', {
       type: dialog.type(),
diff --git a/src/rpc/server/dispatcher.ts b/src/rpc/server/dispatcher.ts
index 57a76cbdbc..e122efc696 100644
--- a/src/rpc/server/dispatcher.ts
+++ b/src/rpc/server/dispatcher.ts
@@ -16,7 +16,7 @@
 
 import { EventEmitter } from 'events';
 import { helper, debugAssert, assert } from '../../helper';
-import { Channel } from '../channels';
+import * as channels from '../channels';
 import { serializeError } from '../serializers';
 import { createScheme, Validator, ValidationError } from '../validator';
 
@@ -36,7 +36,7 @@ export function lookupNullableDispatcher<DispatcherType>(object: any | null): Di
   return object ? lookupDispatcher(object) : undefined;
 }
 
-export class Dispatcher<Type, Initializer> extends EventEmitter implements Channel {
+export class Dispatcher<Type, Initializer> extends EventEmitter implements channels.Channel {
   private _connection: DispatcherConnection;
   private _isScope: boolean;
   // Parent is always "isScope".
diff --git a/src/rpc/server/downloadDispatcher.ts b/src/rpc/server/downloadDispatcher.ts
index fe0f961f0f..450b3c9768 100644
--- a/src/rpc/server/downloadDispatcher.ts
+++ b/src/rpc/server/downloadDispatcher.ts
@@ -15,11 +15,11 @@
  */
 
 import { Download } from '../../download';
-import { DownloadChannel, DownloadInitializer, StreamChannel } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import { StreamDispatcher } from './streamDispatcher';
 
-export class DownloadDispatcher extends Dispatcher<Download, DownloadInitializer> implements DownloadChannel {
+export class DownloadDispatcher extends Dispatcher<Download, channels.DownloadInitializer> implements channels.DownloadChannel {
   constructor(scope: DispatcherScope, download: Download) {
     super(scope, download, 'Download', {
       url: download.url(),
@@ -27,16 +27,16 @@ export class DownloadDispatcher extends Dispatcher<Download, DownloadInitializer
     });
   }
 
-  async path(): Promise<{ value?: string }> {
+  async path(): Promise<channels.DownloadPathResult> {
     const path = await this._object.path();
     return { value: path || undefined };
   }
 
-  async saveAs(params: { path: string }): Promise<void> {
+  async saveAs(params: channels.DownloadSaveAsParams): Promise<void> {
     await this._object.saveAs(params.path);
   }
 
-  async stream(): Promise<{ stream?: StreamChannel }> {
+  async stream(): Promise<channels.DownloadStreamResult> {
     const stream = await this._object.createReadStream();
     if (!stream)
       return {};
@@ -44,7 +44,7 @@ export class DownloadDispatcher extends Dispatcher<Download, DownloadInitializer
     return { stream: new StreamDispatcher(this._scope, stream) };
   }
 
-  async failure(): Promise<{ error?: string }> {
+  async failure(): Promise<channels.DownloadFailureResult> {
     const error = await this._object.failure();
     return { error: error || undefined };
   }
diff --git a/src/rpc/server/electronDispatcher.ts b/src/rpc/server/electronDispatcher.ts
index 5a5d9ee0fb..a046b53d9c 100644
--- a/src/rpc/server/electronDispatcher.ts
+++ b/src/rpc/server/electronDispatcher.ts
@@ -16,24 +16,24 @@
 
 import { Dispatcher, DispatcherScope, lookupDispatcher } from './dispatcher';
 import { Electron, ElectronApplication, ElectronEvents, ElectronPage } from '../../server/electron';
-import { ElectronApplicationChannel, ElectronApplicationInitializer, PageChannel, JSHandleChannel, ElectronInitializer, ElectronChannel, SerializedArgument, ElectronLaunchParams, SerializedValue } from '../channels';
+import * as channels from '../channels';
 import { BrowserContextDispatcher } from './browserContextDispatcher';
 import { PageDispatcher } from './pageDispatcher';
 import { parseArgument, serializeResult } from './jsHandleDispatcher';
 import { createHandle } from './elementHandlerDispatcher';
 
-export class ElectronDispatcher extends Dispatcher<Electron, ElectronInitializer> implements ElectronChannel {
+export class ElectronDispatcher extends Dispatcher<Electron, channels.ElectronInitializer> implements channels.ElectronChannel {
   constructor(scope: DispatcherScope, electron: Electron) {
     super(scope, electron, 'Electron', {}, true);
   }
 
-  async launch(params: ElectronLaunchParams): Promise<{ electronApplication: ElectronApplicationChannel }> {
+  async launch(params: channels.ElectronLaunchParams): Promise<channels.ElectronLaunchResult> {
     const electronApplication = await this._object.launch(params.executablePath, params);
     return { electronApplication: new ElectronApplicationDispatcher(this._scope, electronApplication) };
   }
 }
 
-export class ElectronApplicationDispatcher extends Dispatcher<ElectronApplication, ElectronApplicationInitializer> implements ElectronApplicationChannel {
+export class ElectronApplicationDispatcher extends Dispatcher<ElectronApplication, channels.ElectronApplicationInitializer> implements channels.ElectronApplicationChannel {
   constructor(scope: DispatcherScope, electronApplication: ElectronApplication) {
     super(scope, electronApplication, 'ElectronApplication', {}, true);
     this._dispatchEvent('context', { context: new BrowserContextDispatcher(this._scope, electronApplication.context()) });
@@ -49,17 +49,17 @@ export class ElectronApplicationDispatcher extends Dispatcher<ElectronApplicatio
     });
   }
 
-  async newBrowserWindow(params: { arg: SerializedArgument }): Promise<{ page: PageChannel }> {
+  async newBrowserWindow(params: channels.ElectronApplicationNewBrowserWindowParams): Promise<channels.ElectronApplicationNewBrowserWindowResult> {
     const page = await this._object.newBrowserWindow(parseArgument(params.arg));
-    return { page: lookupDispatcher<PageChannel>(page) };
+    return { page: lookupDispatcher<PageDispatcher>(page) };
   }
 
-  async evaluateExpression(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evaluateExpression(params: channels.ElectronApplicationEvaluateExpressionParams): Promise<channels.ElectronApplicationEvaluateExpressionResult> {
     const handle = this._object._nodeElectronHandle!;
     return { value: serializeResult(await handle._evaluateExpression(params.expression, params.isFunction, true /* returnByValue */, parseArgument(params.arg))) };
   }
 
-  async evaluateExpressionHandle(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ handle: JSHandleChannel }> {
+  async evaluateExpressionHandle(params: channels.ElectronApplicationEvaluateExpressionHandleParams): Promise<channels.ElectronApplicationEvaluateExpressionHandleResult> {
     const handle = this._object._nodeElectronHandle!;
     const result = await handle._evaluateExpression(params.expression, params.isFunction, false /* returnByValue */, parseArgument(params.arg));
     return { handle: createHandle(this._scope, result) };
diff --git a/src/rpc/server/elementHandlerDispatcher.ts b/src/rpc/server/elementHandlerDispatcher.ts
index 8747025ff5..e76e3fb3ac 100644
--- a/src/rpc/server/elementHandlerDispatcher.ts
+++ b/src/rpc/server/elementHandlerDispatcher.ts
@@ -16,8 +16,7 @@
 
 import { ElementHandle } from '../../dom';
 import * as js from '../../javascript';
-import * as types from '../../types';
-import { ElementHandleChannel, FrameChannel, Binary, SerializedArgument, SerializedValue } from '../channels';
+import * as channels from '../channels';
 import { DispatcherScope, lookupNullableDispatcher } from './dispatcher';
 import { JSHandleDispatcher, serializeResult, parseArgument } from './jsHandleDispatcher';
 import { FrameDispatcher } from './frameDispatcher';
@@ -26,7 +25,7 @@ export function createHandle(scope: DispatcherScope, handle: js.JSHandle): JSHan
   return handle.asElement() ? new ElementHandleDispatcher(scope, handle.asElement()!) : new JSHandleDispatcher(scope, handle);
 }
 
-export class ElementHandleDispatcher extends JSHandleDispatcher implements ElementHandleChannel {
+export class ElementHandleDispatcher extends JSHandleDispatcher implements channels.ElementHandleChannel {
   readonly _elementHandle: ElementHandle;
 
   static createNullable(scope: DispatcherScope, handle: ElementHandle | null): ElementHandleDispatcher | undefined {
@@ -40,121 +39,121 @@ export class ElementHandleDispatcher extends JSHandleDispatcher implements Eleme
     this._elementHandle = elementHandle;
   }
 
-  async ownerFrame(): Promise<{ frame?: FrameChannel }> {
+  async ownerFrame(): Promise<channels.ElementHandleOwnerFrameResult> {
     return { frame: lookupNullableDispatcher<FrameDispatcher>(await this._elementHandle.ownerFrame()) };
   }
 
-  async contentFrame(): Promise<{ frame?: FrameChannel }> {
+  async contentFrame(): Promise<channels.ElementHandleContentFrameResult> {
     return { frame: lookupNullableDispatcher<FrameDispatcher>(await this._elementHandle.contentFrame()) };
   }
 
-  async getAttribute(params: { name: string }): Promise<{ value?: string }> {
+  async getAttribute(params: channels.ElementHandleGetAttributeParams): Promise<channels.ElementHandleGetAttributeResult> {
     const value = await this._elementHandle.getAttribute(params.name);
     return { value: value === null ? undefined : value };
   }
 
-  async textContent(): Promise<{ value?: string }> {
+  async textContent(): Promise<channels.ElementHandleTextContentResult> {
     const value = await this._elementHandle.textContent();
     return { value: value === null ? undefined : value };
   }
 
-  async innerText(): Promise<{ value: string }> {
+  async innerText(): Promise<channels.ElementHandleInnerTextResult> {
     return { value: await this._elementHandle.innerText() };
   }
 
-  async innerHTML(): Promise<{ value: string }> {
+  async innerHTML(): Promise<channels.ElementHandleInnerHTMLResult> {
     return { value: await this._elementHandle.innerHTML() };
   }
 
-  async dispatchEvent(params: { type: string, eventInit: SerializedArgument }) {
+  async dispatchEvent(params: channels.ElementHandleDispatchEventParams): Promise<void> {
     await this._elementHandle.dispatchEvent(params.type, parseArgument(params.eventInit));
   }
 
-  async scrollIntoViewIfNeeded(params: types.TimeoutOptions) {
+  async scrollIntoViewIfNeeded(params: channels.ElementHandleScrollIntoViewIfNeededParams): Promise<void> {
     await this._elementHandle.scrollIntoViewIfNeeded(params);
   }
 
-  async hover(params: types.PointerActionOptions & types.PointerActionWaitOptions) {
+  async hover(params: channels.ElementHandleHoverParams): Promise<void> {
     await this._elementHandle.hover(params);
   }
 
-  async click(params: types.MouseClickOptions & types.PointerActionWaitOptions & types.NavigatingActionWaitOptions) {
+  async click(params: channels.ElementHandleClickParams): Promise<void> {
     await this._elementHandle.click(params);
   }
 
-  async dblclick(params: types.MouseMultiClickOptions & types.PointerActionWaitOptions & types.NavigatingActionWaitOptions) {
+  async dblclick(params: channels.ElementHandleDblclickParams): Promise<void> {
     await this._elementHandle.dblclick(params);
   }
 
-  async selectOption(params: { elements?: ElementHandleChannel[], options?: types.SelectOption[] } & types.NavigatingActionWaitOptions): Promise<{ values: string[] }> {
+  async selectOption(params: channels.ElementHandleSelectOptionParams): Promise<channels.ElementHandleSelectOptionResult> {
     const elements = (params.elements || []).map(e => (e as ElementHandleDispatcher)._elementHandle);
     return { values: await this._elementHandle.selectOption(elements, params.options || [], params) };
   }
 
-  async fill(params: { value: string } & types.NavigatingActionWaitOptions) {
+  async fill(params: channels.ElementHandleFillParams): Promise<void> {
     await this._elementHandle.fill(params.value, params);
   }
 
-  async selectText(params: types.TimeoutOptions) {
+  async selectText(params: channels.ElementHandleSelectTextParams): Promise<void> {
     await this._elementHandle.selectText(params);
   }
 
-  async setInputFiles(params: { files: { name: string, mimeType: string, buffer: string }[] } & types.NavigatingActionWaitOptions) {
+  async setInputFiles(params: channels.ElementHandleSetInputFilesParams): Promise<void> {
     await this._elementHandle.setInputFiles(params.files, params);
   }
 
-  async focus() {
+  async focus(): Promise<void> {
     await this._elementHandle.focus();
   }
 
-  async type(params: { text: string } & { delay?: number } & types.NavigatingActionWaitOptions) {
+  async type(params: channels.ElementHandleTypeParams): Promise<void> {
     await this._elementHandle.type(params.text, params);
   }
 
-  async press(params: { key: string } & { delay?: number } & types.NavigatingActionWaitOptions) {
+  async press(params: channels.ElementHandlePressParams): Promise<void> {
     await this._elementHandle.press(params.key, params);
   }
 
-  async check(params: types.PointerActionWaitOptions & types.NavigatingActionWaitOptions) {
+  async check(params: channels.ElementHandleCheckParams): Promise<void> {
     await this._elementHandle.check(params);
   }
 
-  async uncheck(params: types.PointerActionWaitOptions & types.NavigatingActionWaitOptions) {
+  async uncheck(params: channels.ElementHandleUncheckParams): Promise<void> {
     await this._elementHandle.uncheck(params);
   }
 
-  async boundingBox(): Promise<{ value?: types.Rect }> {
+  async boundingBox(): Promise<channels.ElementHandleBoundingBoxResult> {
     const value = await this._elementHandle.boundingBox();
     return { value: value || undefined };
   }
 
-  async screenshot(params: types.ElementScreenshotOptions): Promise<{ binary: Binary }> {
+  async screenshot(params: channels.ElementHandleScreenshotParams): Promise<channels.ElementHandleScreenshotResult> {
     return { binary: (await this._elementHandle.screenshot(params)).toString('base64') };
   }
 
-  async querySelector(params: { selector: string }): Promise<{ element?: ElementHandleChannel }> {
+  async querySelector(params: channels.ElementHandleQuerySelectorParams): Promise<channels.ElementHandleQuerySelectorResult> {
     const handle = await this._elementHandle.$(params.selector);
     return { element: handle ? new ElementHandleDispatcher(this._scope, handle) : undefined };
   }
 
-  async querySelectorAll(params: { selector: string }): Promise<{ elements: ElementHandleChannel[] }> {
+  async querySelectorAll(params: channels.ElementHandleQuerySelectorAllParams): Promise<channels.ElementHandleQuerySelectorAllResult> {
     const elements = await this._elementHandle.$$(params.selector);
     return { elements: elements.map(e => new ElementHandleDispatcher(this._scope, e)) };
   }
 
-  async evalOnSelector(params: { selector: string, expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evalOnSelector(params: channels.ElementHandleEvalOnSelectorParams): Promise<channels.ElementHandleEvalOnSelectorResult> {
     return { value: serializeResult(await this._elementHandle._$evalExpression(params.selector, params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async evalOnSelectorAll(params: { selector: string, expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evalOnSelectorAll(params: channels.ElementHandleEvalOnSelectorAllParams): Promise<channels.ElementHandleEvalOnSelectorAllResult> {
     return { value: serializeResult(await this._elementHandle._$$evalExpression(params.selector, params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async waitForElementState(params: { state: 'visible' | 'hidden' | 'stable' | 'enabled' | 'disabled' } & types.TimeoutOptions): Promise<void> {
+  async waitForElementState(params: channels.ElementHandleWaitForElementStateParams): Promise<void> {
     await this._elementHandle.waitForElementState(params.state, params);
   }
 
-  async waitForSelector(params: { selector: string } & types.WaitForElementOptions): Promise<{ element?: ElementHandleChannel }> {
+  async waitForSelector(params: channels.ElementHandleWaitForSelectorParams): Promise<channels.ElementHandleWaitForSelectorResult> {
     return { element: ElementHandleDispatcher.createNullable(this._scope, await this._elementHandle.waitForSelector(params.selector, params)) };
   }
 }
diff --git a/src/rpc/server/frameDispatcher.ts b/src/rpc/server/frameDispatcher.ts
index 19a6815e0e..fa0d04b4f9 100644
--- a/src/rpc/server/frameDispatcher.ts
+++ b/src/rpc/server/frameDispatcher.ts
@@ -16,13 +16,13 @@
 
 import { Frame, kAddLifecycleEvent, kRemoveLifecycleEvent, kNavigationEvent, NavigationEvent } from '../../frames';
 import * as types from '../../types';
-import { ElementHandleChannel, FrameChannel, FrameInitializer, JSHandleChannel, ResponseChannel, SerializedArgument, FrameWaitForFunctionParams, SerializedValue } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope, lookupNullableDispatcher, existingDispatcher } from './dispatcher';
 import { ElementHandleDispatcher, createHandle } from './elementHandlerDispatcher';
 import { parseArgument, serializeResult } from './jsHandleDispatcher';
 import { ResponseDispatcher, RequestDispatcher } from './networkDispatchers';
 
-export class FrameDispatcher extends Dispatcher<Frame, FrameInitializer> implements FrameChannel {
+export class FrameDispatcher extends Dispatcher<Frame, channels.FrameInitializer> implements channels.FrameChannel {
   private _frame: Frame;
 
   static from(scope: DispatcherScope, frame: Frame): FrameDispatcher {
@@ -52,127 +52,127 @@ export class FrameDispatcher extends Dispatcher<Frame, FrameInitializer> impleme
     });
   }
 
-  async goto(params: { url: string } & types.GotoOptions): Promise<{ response?: ResponseChannel }> {
+  async goto(params: channels.FrameGotoParams): Promise<channels.FrameGotoResult> {
     return { response: lookupNullableDispatcher<ResponseDispatcher>(await this._frame.goto(params.url, params)) };
   }
 
-  async frameElement(): Promise<{ element: ElementHandleChannel }> {
+  async frameElement(): Promise<channels.FrameFrameElementResult> {
     return { element: new ElementHandleDispatcher(this._scope, await this._frame.frameElement()) };
   }
 
-  async evaluateExpression(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evaluateExpression(params: channels.FrameEvaluateExpressionParams): Promise<channels.FrameEvaluateExpressionResult> {
     return { value: serializeResult(await this._frame._evaluateExpression(params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async evaluateExpressionHandle(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ handle: JSHandleChannel }> {
+  async evaluateExpressionHandle(params: channels.FrameEvaluateExpressionHandleParams): Promise<channels.FrameEvaluateExpressionHandleResult> {
     return { handle: createHandle(this._scope, await this._frame._evaluateExpressionHandle(params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async waitForSelector(params: { selector: string } & types.WaitForElementOptions): Promise<{ element?: ElementHandleChannel }> {
+  async waitForSelector(params: channels.FrameWaitForSelectorParams): Promise<channels.FrameWaitForSelectorResult> {
     return { element: ElementHandleDispatcher.createNullable(this._scope, await this._frame.waitForSelector(params.selector, params)) };
   }
 
-  async dispatchEvent(params: { selector: string, type: string, eventInit: SerializedArgument } & types.TimeoutOptions): Promise<void> {
+  async dispatchEvent(params: channels.FrameDispatchEventParams): Promise<void> {
     return this._frame.dispatchEvent(params.selector, params.type, parseArgument(params.eventInit), params);
   }
 
-  async evalOnSelector(params: { selector: string, expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evalOnSelector(params: channels.FrameEvalOnSelectorParams): Promise<channels.FrameEvalOnSelectorResult> {
     return { value: serializeResult(await this._frame._$evalExpression(params.selector, params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async evalOnSelectorAll(params: { selector: string, expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evalOnSelectorAll(params: channels.FrameEvalOnSelectorAllParams): Promise<channels.FrameEvalOnSelectorAllResult> {
     return { value: serializeResult(await this._frame._$$evalExpression(params.selector, params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async querySelector(params: { selector: string }): Promise<{ element?: ElementHandleChannel }> {
+  async querySelector(params: channels.FrameQuerySelectorParams): Promise<channels.FrameQuerySelectorResult> {
     return { element: ElementHandleDispatcher.createNullable(this._scope, await this._frame.$(params.selector)) };
   }
 
-  async querySelectorAll(params: { selector: string }): Promise<{ elements: ElementHandleChannel[] }> {
+  async querySelectorAll(params: channels.FrameQuerySelectorAllParams): Promise<channels.FrameQuerySelectorAllResult> {
     const elements = await this._frame.$$(params.selector);
     return { elements: elements.map(e => new ElementHandleDispatcher(this._scope, e)) };
   }
 
-  async content(): Promise<{ value: string }> {
+  async content(): Promise<channels.FrameContentResult> {
     return { value: await this._frame.content() };
   }
 
-  async setContent(params: { html: string } & types.NavigateOptions): Promise<void> {
+  async setContent(params: channels.FrameSetContentParams): Promise<void> {
     await this._frame.setContent(params.html, params);
   }
 
-  async addScriptTag(params: { url?: string, content?: string, type?: string }): Promise<{ element: ElementHandleChannel }> {
+  async addScriptTag(params: channels.FrameAddScriptTagParams): Promise<channels.FrameAddScriptTagResult> {
     return { element: new ElementHandleDispatcher(this._scope, await this._frame.addScriptTag(params)) };
   }
 
-  async addStyleTag(params: { url?: string, content?: string }): Promise<{ element: ElementHandleChannel }> {
+  async addStyleTag(params: channels.FrameAddStyleTagParams): Promise<channels.FrameAddStyleTagResult> {
     return { element: new ElementHandleDispatcher(this._scope, await this._frame.addStyleTag(params)) };
   }
 
-  async click(params: { selector: string } & types.PointerActionOptions & types.MouseClickOptions & types.TimeoutOptions & { force?: boolean } & { noWaitAfter?: boolean }): Promise<void> {
+  async click(params: channels.FrameClickParams): Promise<void> {
     await this._frame.click(params.selector, params);
   }
 
-  async dblclick(params: { selector: string } & types.PointerActionOptions & types.MouseMultiClickOptions & types.TimeoutOptions & { force?: boolean }): Promise<void> {
+  async dblclick(params: channels.FrameDblclickParams): Promise<void> {
     await this._frame.dblclick(params.selector, params);
   }
 
-  async fill(params: { selector: string, value: string } & types.NavigatingActionWaitOptions): Promise<void> {
+  async fill(params: channels.FrameFillParams): Promise<void> {
     await this._frame.fill(params.selector, params.value, params);
   }
 
-  async focus(params: { selector: string } & types.TimeoutOptions): Promise<void> {
+  async focus(params: channels.FrameFocusParams): Promise<void> {
     await this._frame.focus(params.selector, params);
   }
 
-  async textContent(params: { selector: string } & types.TimeoutOptions): Promise<{ value?: string }> {
+  async textContent(params: channels.FrameTextContentParams): Promise<channels.FrameTextContentResult> {
     const value = await this._frame.textContent(params.selector, params);
     return { value: value === null ? undefined : value };
   }
 
-  async innerText(params: { selector: string } & types.TimeoutOptions): Promise<{ value: string }> {
+  async innerText(params: channels.FrameInnerTextParams): Promise<channels.FrameInnerTextResult> {
     return { value: await this._frame.innerText(params.selector, params) };
   }
 
-  async innerHTML(params: { selector: string } & types.TimeoutOptions): Promise<{ value: string }> {
+  async innerHTML(params: channels.FrameInnerHTMLParams): Promise<channels.FrameInnerHTMLResult> {
     return { value: await this._frame.innerHTML(params.selector, params) };
   }
 
-  async getAttribute(params: { selector: string, name: string } & types.TimeoutOptions): Promise<{ value?: string }> {
+  async getAttribute(params: channels.FrameGetAttributeParams): Promise<channels.FrameGetAttributeResult> {
     const value = await this._frame.getAttribute(params.selector, params.name, params);
     return { value: value === null ? undefined : value };
   }
 
-  async hover(params: { selector: string } & types.PointerActionOptions & types.TimeoutOptions & { force?: boolean }): Promise<void> {
+  async hover(params: channels.FrameHoverParams): Promise<void> {
     await this._frame.hover(params.selector, params);
   }
 
-  async selectOption(params: { selector: string, elements?: ElementHandleChannel[], options?: types.SelectOption[] } & types.NavigatingActionWaitOptions): Promise<{ values: string[] }> {
+  async selectOption(params: channels.FrameSelectOptionParams): Promise<channels.FrameSelectOptionResult> {
     const elements = (params.elements || []).map(e => (e as ElementHandleDispatcher)._elementHandle);
     return { values: await this._frame.selectOption(params.selector, elements, params.options || [], params) };
   }
 
-  async setInputFiles(params: { selector: string, files: { name: string, mimeType: string, buffer: string }[] } & types.NavigatingActionWaitOptions): Promise<void> {
+  async setInputFiles(params: channels.FrameSetInputFilesParams): Promise<void> {
     await this._frame.setInputFiles(params.selector, params.files, params);
   }
 
-  async type(params: { selector: string, text: string } & { delay?: number | undefined } & types.TimeoutOptions & { noWaitAfter?: boolean }): Promise<void> {
+  async type(params: channels.FrameTypeParams): Promise<void> {
     await this._frame.type(params.selector, params.text, params);
   }
 
-  async press(params: { selector: string, key: string } & { delay?: number | undefined } & types.TimeoutOptions & { noWaitAfter?: boolean }): Promise<void> {
+  async press(params: channels.FramePressParams): Promise<void> {
     await this._frame.press(params.selector, params.key, params);
   }
 
-  async check(params: { selector: string } & types.TimeoutOptions & { force?: boolean } & { noWaitAfter?: boolean }): Promise<void> {
+  async check(params: channels.FrameCheckParams): Promise<void> {
     await this._frame.check(params.selector, params);
   }
 
-  async uncheck(params: { selector: string } & types.TimeoutOptions & { force?: boolean } & { noWaitAfter?: boolean }): Promise<void> {
+  async uncheck(params: channels.FrameUncheckParams): Promise<void> {
     await this._frame.uncheck(params.selector, params);
   }
 
-  async waitForFunction(params: FrameWaitForFunctionParams): Promise<{ handle: JSHandleChannel }> {
+  async waitForFunction(params: channels.FrameWaitForFunctionParams): Promise<channels.FrameWaitForFunctionResult> {
     const options = {
       ...params,
       polling: params.pollingInterval === undefined ? 'raf' as const : params.pollingInterval
@@ -180,7 +180,7 @@ export class FrameDispatcher extends Dispatcher<Frame, FrameInitializer> impleme
     return { handle: createHandle(this._scope, await this._frame._waitForFunctionExpression(params.expression, params.isFunction, parseArgument(params.arg), options)) };
   }
 
-  async title(): Promise<{ value: string }> {
+  async title(): Promise<channels.FrameTitleResult> {
     return { value: await this._frame.title() };
   }
 }
diff --git a/src/rpc/server/jsHandleDispatcher.ts b/src/rpc/server/jsHandleDispatcher.ts
index 0b9c72cd47..9fc363064f 100644
--- a/src/rpc/server/jsHandleDispatcher.ts
+++ b/src/rpc/server/jsHandleDispatcher.ts
@@ -15,12 +15,12 @@
  */
 
 import * as js from '../../javascript';
-import { JSHandleChannel, JSHandleInitializer, SerializedArgument, SerializedValue } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import { createHandle } from './elementHandlerDispatcher';
 import { parseSerializedValue, serializeValue } from '../serializers';
 
-export class JSHandleDispatcher extends Dispatcher<js.JSHandle, JSHandleInitializer> implements JSHandleChannel {
+export class JSHandleDispatcher extends Dispatcher<js.JSHandle, channels.JSHandleInitializer> implements channels.JSHandleChannel {
 
   constructor(scope: DispatcherScope, jsHandle: js.JSHandle) {
     super(scope, jsHandle, jsHandle.asElement() ? 'ElementHandle' : 'JSHandle', {
@@ -29,21 +29,21 @@ export class JSHandleDispatcher extends Dispatcher<js.JSHandle, JSHandleInitiali
     jsHandle._setPreviewCallback(preview => this._dispatchEvent('previewUpdated', { preview }));
   }
 
-  async evaluateExpression(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evaluateExpression(params: channels.JSHandleEvaluateExpressionParams): Promise<channels.JSHandleEvaluateExpressionResult> {
     return { value: serializeResult(await this._object._evaluateExpression(params.expression, params.isFunction, true /* returnByValue */, parseArgument(params.arg))) };
   }
 
-  async evaluateExpressionHandle(params: { expression: string, isFunction: boolean, arg: SerializedArgument}): Promise<{ handle: JSHandleChannel }> {
+  async evaluateExpressionHandle(params: channels.JSHandleEvaluateExpressionHandleParams): Promise<channels.JSHandleEvaluateExpressionHandleResult> {
     const jsHandle = await this._object._evaluateExpression(params.expression, params.isFunction, false /* returnByValue */, parseArgument(params.arg));
     return { handle: createHandle(this._scope, jsHandle) };
   }
 
-  async getProperty(params: { name: string }): Promise<{ handle: JSHandleChannel }> {
+  async getProperty(params: channels.JSHandleGetPropertyParams): Promise<channels.JSHandleGetPropertyResult> {
     const jsHandle = await this._object.getProperty(params.name);
     return { handle: createHandle(this._scope, jsHandle) };
   }
 
-  async getPropertyList(): Promise<{ properties: { name: string, value: JSHandleChannel }[] }> {
+  async getPropertyList(): Promise<channels.JSHandleGetPropertyListResult> {
     const map = await this._object.getProperties();
     const properties = [];
     for (const [name, value] of map)
@@ -51,7 +51,7 @@ export class JSHandleDispatcher extends Dispatcher<js.JSHandle, JSHandleInitiali
     return { properties };
   }
 
-  async jsonValue(): Promise<{ value: SerializedValue }> {
+  async jsonValue(): Promise<channels.JSHandleJsonValueResult> {
     return { value: serializeResult(await this._object.jsonValue()) };
   }
 
@@ -62,13 +62,14 @@ export class JSHandleDispatcher extends Dispatcher<js.JSHandle, JSHandleInitiali
 
 // Generic channel parser converts guids to JSHandleDispatchers,
 // and this function takes care of coverting them into underlying JSHandles.
-export function parseArgument(arg: SerializedArgument): any {
+export function parseArgument(arg: channels.SerializedArgument): any {
   return parseSerializedValue(arg.value, arg.handles.map(a => (a as JSHandleDispatcher)._object));
 }
-export function parseValue(v: SerializedValue): any {
+
+export function parseValue(v: channels.SerializedValue): any {
   return parseSerializedValue(v, []);
 }
 
-export function serializeResult(arg: any): SerializedValue {
+export function serializeResult(arg: any): channels.SerializedValue {
   return serializeValue(arg, value => ({ fallThrough: value }), new Set());
 }
diff --git a/src/rpc/server/networkDispatchers.ts b/src/rpc/server/networkDispatchers.ts
index 881d2c32cd..be8c0d8caf 100644
--- a/src/rpc/server/networkDispatchers.ts
+++ b/src/rpc/server/networkDispatchers.ts
@@ -15,12 +15,11 @@
  */
 
 import { Request, Response, Route } from '../../network';
-import { RequestChannel, ResponseChannel, RouteChannel, ResponseInitializer, RequestInitializer, RouteInitializer, Binary } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope, lookupNullableDispatcher, existingDispatcher } from './dispatcher';
 import { FrameDispatcher } from './frameDispatcher';
-import * as types from '../../types';
 
-export class RequestDispatcher extends Dispatcher<Request, RequestInitializer> implements RequestChannel {
+export class RequestDispatcher extends Dispatcher<Request, channels.RequestInitializer> implements channels.RequestChannel {
 
   static from(scope: DispatcherScope, request: Request): RequestDispatcher {
     const result = existingDispatcher<RequestDispatcher>(request);
@@ -45,12 +44,12 @@ export class RequestDispatcher extends Dispatcher<Request, RequestInitializer> i
     });
   }
 
-  async response(): Promise<{ response?: ResponseChannel }> {
+  async response(): Promise<channels.RequestResponseResult> {
     return { response: lookupNullableDispatcher<ResponseDispatcher>(await this._object.response()) };
   }
 }
 
-export class ResponseDispatcher extends Dispatcher<Response, ResponseInitializer> implements ResponseChannel {
+export class ResponseDispatcher extends Dispatcher<Response, channels.ResponseInitializer> implements channels.ResponseChannel {
 
   constructor(scope: DispatcherScope, response: Response) {
     super(scope, response, 'Response', {
@@ -63,16 +62,16 @@ export class ResponseDispatcher extends Dispatcher<Response, ResponseInitializer
     });
   }
 
-  async finished(): Promise<{ error?: string }> {
+  async finished(): Promise<channels.ResponseFinishedResult> {
     return await this._object._finishedPromise;
   }
 
-  async body(): Promise<{ binary: Binary }> {
+  async body(): Promise<channels.ResponseBodyResult> {
     return { binary: (await this._object.body()).toString('base64') };
   }
 }
 
-export class RouteDispatcher extends Dispatcher<Route, RouteInitializer> implements RouteChannel {
+export class RouteDispatcher extends Dispatcher<Route, channels.RouteInitializer> implements channels.RouteChannel {
 
   constructor(scope: DispatcherScope, route: Route) {
     super(scope, route, 'Route', {
@@ -81,7 +80,7 @@ export class RouteDispatcher extends Dispatcher<Route, RouteInitializer> impleme
     });
   }
 
-  async continue(params: { method?: string, headers?: types.HeadersArray, postData?: string }): Promise<void> {
+  async continue(params: channels.RouteContinueParams): Promise<void> {
     await this._object.continue({
       method: params.method,
       headers: params.headers,
@@ -89,11 +88,11 @@ export class RouteDispatcher extends Dispatcher<Route, RouteInitializer> impleme
     });
   }
 
-  async fulfill(params: types.NormalizedFulfillResponse): Promise<void> {
+  async fulfill(params: channels.RouteFulfillParams): Promise<void> {
     await this._object.fulfill(params);
   }
 
-  async abort(params: { errorCode?: string }): Promise<void> {
+  async abort(params: channels.RouteAbortParams): Promise<void> {
     await this._object.abort(params.errorCode || 'failed');
   }
 }
diff --git a/src/rpc/server/pageDispatcher.ts b/src/rpc/server/pageDispatcher.ts
index 39e19b17f5..d23a402e64 100644
--- a/src/rpc/server/pageDispatcher.ts
+++ b/src/rpc/server/pageDispatcher.ts
@@ -19,8 +19,7 @@ import { Events } from '../../events';
 import { Frame } from '../../frames';
 import { Request } from '../../network';
 import { Page, Worker } from '../../page';
-import * as types from '../../types';
-import { BindingCallChannel, BindingCallInitializer, ElementHandleChannel, PageChannel, PageInitializer, ResponseChannel, WorkerInitializer, WorkerChannel, JSHandleChannel, Binary, SerializedArgument, PagePdfParams, SerializedError, PageAccessibilitySnapshotResult, SerializedValue, PageEmulateMediaParams } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope, lookupDispatcher, lookupNullableDispatcher } from './dispatcher';
 import { parseError, serializeError } from '../serializers';
 import { ConsoleMessageDispatcher } from './consoleMessageDispatcher';
@@ -33,7 +32,7 @@ import { ElementHandleDispatcher, createHandle } from './elementHandlerDispatche
 import { FileChooser } from '../../fileChooser';
 import { CRCoverage } from '../../chromium/crCoverage';
 
-export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements PageChannel {
+export class PageDispatcher extends Dispatcher<Page, channels.PageInitializer> implements channels.PageChannel {
   private _page: Page;
 
   constructor(scope: DispatcherScope, page: Page) {
@@ -70,19 +69,19 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
     page.on(Events.Page.Worker, worker => this._dispatchEvent('worker', { worker: new WorkerDispatcher(this._scope, worker) }));
   }
 
-  async setDefaultNavigationTimeoutNoReply(params: { timeout: number }) {
+  async setDefaultNavigationTimeoutNoReply(params: channels.PageSetDefaultNavigationTimeoutNoReplyParams): Promise<void> {
     this._page.setDefaultNavigationTimeout(params.timeout);
   }
 
-  async setDefaultTimeoutNoReply(params: { timeout: number }) {
+  async setDefaultTimeoutNoReply(params: channels.PageSetDefaultTimeoutNoReplyParams): Promise<void> {
     this._page.setDefaultTimeout(params.timeout);
   }
 
-  async opener(): Promise<{ page?: PageChannel }> {
+  async opener(): Promise<channels.PageOpenerResult> {
     return { page: lookupNullableDispatcher<PageDispatcher>(await this._page.opener()) };
   }
 
-  async exposeBinding(params: { name: string }): Promise<void> {
+  async exposeBinding(params: channels.PageExposeBindingParams): Promise<void> {
     await this._page.exposeBinding(params.name, (source, ...args) => {
       const binding = new BindingCallDispatcher(this._scope, params.name, source, args);
       this._dispatchEvent('bindingCall', { binding });
@@ -90,38 +89,38 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
     });
   }
 
-  async setExtraHTTPHeaders(params: { headers: types.HeadersArray }): Promise<void> {
+  async setExtraHTTPHeaders(params: channels.PageSetExtraHTTPHeadersParams): Promise<void> {
     await this._page.setExtraHTTPHeaders(params.headers);
   }
 
-  async reload(params: types.NavigateOptions): Promise<{ response?: ResponseChannel }> {
+  async reload(params: channels.PageReloadParams): Promise<channels.PageReloadResult> {
     return { response: lookupNullableDispatcher<ResponseDispatcher>(await this._page.reload(params)) };
   }
 
-  async goBack(params: types.NavigateOptions): Promise<{ response?: ResponseChannel }> {
+  async goBack(params: channels.PageGoBackParams): Promise<channels.PageGoBackResult> {
     return { response: lookupNullableDispatcher<ResponseDispatcher>(await this._page.goBack(params)) };
   }
 
-  async goForward(params: types.NavigateOptions): Promise<{ response?: ResponseChannel }> {
+  async goForward(params: channels.PageGoForwardParams): Promise<channels.PageGoForwardResult> {
     return { response: lookupNullableDispatcher<ResponseDispatcher>(await this._page.goForward(params)) };
   }
 
-  async emulateMedia(params: PageEmulateMediaParams): Promise<void> {
+  async emulateMedia(params: channels.PageEmulateMediaParams): Promise<void> {
     await this._page.emulateMedia({
       media: params.media === 'null' ? null : params.media,
       colorScheme: params.colorScheme === 'null' ? null : params.colorScheme,
     });
   }
 
-  async setViewportSize(params: { viewportSize: types.Size }): Promise<void> {
+  async setViewportSize(params: channels.PageSetViewportSizeParams): Promise<void> {
     await this._page.setViewportSize(params.viewportSize);
   }
 
-  async addInitScript(params: { source: string }): Promise<void> {
+  async addInitScript(params: channels.PageAddInitScriptParams): Promise<void> {
     await this._page._addInitScriptExpression(params.source);
   }
 
-  async setNetworkInterceptionEnabled(params: { enabled: boolean }): Promise<void> {
+  async setNetworkInterceptionEnabled(params: channels.PageSetNetworkInterceptionEnabledParams): Promise<void> {
     if (!params.enabled) {
       await this._page._setRequestInterceptor(undefined);
       return;
@@ -131,55 +130,55 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
     });
   }
 
-  async screenshot(params: types.ScreenshotOptions): Promise<{ binary: Binary }> {
+  async screenshot(params: channels.PageScreenshotParams): Promise<channels.PageScreenshotResult> {
     return { binary: (await this._page.screenshot(params)).toString('base64') };
   }
 
-  async close(params: { runBeforeUnload?: boolean }): Promise<void> {
+  async close(params: channels.PageCloseParams): Promise<void> {
     await this._page.close(params);
   }
 
-  async setFileChooserInterceptedNoReply(params: { intercepted: boolean }) {
+  async setFileChooserInterceptedNoReply(params: channels.PageSetFileChooserInterceptedNoReplyParams): Promise<void> {
     await this._page._setFileChooserIntercepted(params.intercepted);
   }
 
-  async keyboardDown(params: { key: string }): Promise<void> {
+  async keyboardDown(params: channels.PageKeyboardDownParams): Promise<void> {
     await this._page.keyboard.down(params.key);
   }
 
-  async keyboardUp(params: { key: string }): Promise<void> {
+  async keyboardUp(params: channels.PageKeyboardUpParams): Promise<void> {
     await this._page.keyboard.up(params.key);
   }
 
-  async keyboardInsertText(params: { text: string }): Promise<void> {
+  async keyboardInsertText(params: channels.PageKeyboardInsertTextParams): Promise<void> {
     await this._page.keyboard.insertText(params.text);
   }
 
-  async keyboardType(params: { text: string, delay?: number }): Promise<void> {
+  async keyboardType(params: channels.PageKeyboardTypeParams): Promise<void> {
     await this._page.keyboard.type(params.text, params);
   }
 
-  async keyboardPress(params: { key: string, delay?: number }): Promise<void> {
+  async keyboardPress(params: channels.PageKeyboardPressParams): Promise<void> {
     await this._page.keyboard.press(params.key, params);
   }
 
-  async mouseMove(params: { x: number, y: number, steps?: number }): Promise<void> {
+  async mouseMove(params: channels.PageMouseMoveParams): Promise<void> {
     await this._page.mouse.move(params.x, params.y, params);
   }
 
-  async mouseDown(params: { button?: types.MouseButton, clickCount?: number }): Promise<void> {
+  async mouseDown(params: channels.PageMouseDownParams): Promise<void> {
     await this._page.mouse.down(params);
   }
 
-  async mouseUp(params: { button?: types.MouseButton, clickCount?: number }): Promise<void> {
+  async mouseUp(params: channels.PageMouseUpParams): Promise<void> {
     await this._page.mouse.up(params);
   }
 
-  async mouseClick(params: { x: number, y: number, delay?: number, button?: types.MouseButton, clickCount?: number }): Promise<void> {
+  async mouseClick(params: channels.PageMouseClickParams): Promise<void> {
     await this._page.mouse.click(params.x, params.y, params);
   }
 
-  async accessibilitySnapshot(params: { interestingOnly?: boolean, root?: ElementHandleChannel }): Promise<PageAccessibilitySnapshotResult> {
+  async accessibilitySnapshot(params: channels.PageAccessibilitySnapshotParams): Promise<channels.PageAccessibilitySnapshotResult> {
     const rootAXNode = await this._page.accessibility.snapshot({
       interestingOnly: params.interestingOnly,
       root: params.root ? (params.root as ElementHandleDispatcher)._elementHandle : undefined
@@ -187,7 +186,7 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
     return { rootAXNode: rootAXNode || undefined };
   }
 
-  async pdf(params: PagePdfParams): Promise<{ pdf: Binary }> {
+  async pdf(params: channels.PagePdfParams): Promise<channels.PagePdfResult> {
     if (!this._page.pdf)
       throw new Error('PDF generation is only supported for Headless Chromium');
     const buffer = await this._page.pdf(params);
@@ -198,22 +197,22 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
     await this._page.bringToFront();
   }
 
-  async crStartJSCoverage(params: types.JSCoverageOptions): Promise<void> {
+  async crStartJSCoverage(params: channels.PageCrStartJSCoverageParams): Promise<void> {
     const coverage = this._page.coverage as CRCoverage;
     await coverage.startJSCoverage(params);
   }
 
-  async crStopJSCoverage(): Promise<{ entries: types.JSCoverageEntry[] }> {
+  async crStopJSCoverage(): Promise<channels.PageCrStopJSCoverageResult> {
     const coverage = this._page.coverage as CRCoverage;
     return { entries: await coverage.stopJSCoverage() };
   }
 
-  async crStartCSSCoverage(params: types.CSSCoverageOptions): Promise<void> {
+  async crStartCSSCoverage(params: channels.PageCrStartCSSCoverageParams): Promise<void> {
     const coverage = this._page.coverage as CRCoverage;
     await coverage.startCSSCoverage(params);
   }
 
-  async crStopCSSCoverage(): Promise<{ entries: types.CSSCoverageEntry[] }> {
+  async crStopCSSCoverage(): Promise<channels.PageCrStopCSSCoverageResult> {
     const coverage = this._page.coverage as CRCoverage;
     return { entries: await coverage.stopCSSCoverage() };
   }
@@ -228,7 +227,7 @@ export class PageDispatcher extends Dispatcher<Page, PageInitializer> implements
 }
 
 
-export class WorkerDispatcher extends Dispatcher<Worker, WorkerInitializer> implements WorkerChannel {
+export class WorkerDispatcher extends Dispatcher<Worker, channels.WorkerInitializer> implements channels.WorkerChannel {
   constructor(scope: DispatcherScope, worker: Worker) {
     super(scope, worker, 'Worker', {
       url: worker.url()
@@ -236,16 +235,16 @@ export class WorkerDispatcher extends Dispatcher<Worker, WorkerInitializer> impl
     worker.on(Events.Worker.Close, () => this._dispatchEvent('close'));
   }
 
-  async evaluateExpression(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ value: SerializedValue }> {
+  async evaluateExpression(params: channels.WorkerEvaluateExpressionParams): Promise<channels.WorkerEvaluateExpressionResult> {
     return { value: serializeResult(await this._object._evaluateExpression(params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 
-  async evaluateExpressionHandle(params: { expression: string, isFunction: boolean, arg: SerializedArgument }): Promise<{ handle: JSHandleChannel }> {
+  async evaluateExpressionHandle(params: channels.WorkerEvaluateExpressionHandleParams): Promise<channels.WorkerEvaluateExpressionHandleResult> {
     return { handle: createHandle(this._scope, await this._object._evaluateExpressionHandle(params.expression, params.isFunction, parseArgument(params.arg))) };
   }
 }
 
-export class BindingCallDispatcher extends Dispatcher<{}, BindingCallInitializer> implements BindingCallChannel {
+export class BindingCallDispatcher extends Dispatcher<{}, channels.BindingCallInitializer> implements channels.BindingCallChannel {
   private _resolve: ((arg: any) => void) | undefined;
   private _reject: ((error: any) => void) | undefined;
   private _promise: Promise<any>;
@@ -266,11 +265,11 @@ export class BindingCallDispatcher extends Dispatcher<{}, BindingCallInitializer
     return this._promise;
   }
 
-  async resolve(params: { result: SerializedArgument }) {
+  async resolve(params: channels.BindingCallResolveParams): Promise<void> {
     this._resolve!(parseArgument(params.result));
   }
 
-  async reject(params: { error: SerializedError }) {
+  async reject(params: channels.BindingCallRejectParams): Promise<void> {
     this._reject!(parseError(params.error));
   }
 }
diff --git a/src/rpc/server/playwrightDispatcher.ts b/src/rpc/server/playwrightDispatcher.ts
index 4b9b52b6f9..5d22da73f8 100644
--- a/src/rpc/server/playwrightDispatcher.ts
+++ b/src/rpc/server/playwrightDispatcher.ts
@@ -15,7 +15,7 @@
  */
 
 import { Playwright } from '../../server/playwright';
-import { PlaywrightChannel, PlaywrightInitializer } from '../channels';
+import * as channels from '../channels';
 import { BrowserTypeDispatcher } from './browserTypeDispatcher';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import { SelectorsDispatcher } from './selectorsDispatcher';
@@ -23,7 +23,7 @@ import { Electron } from '../../server/electron';
 import { ElectronDispatcher } from './electronDispatcher';
 import { DeviceDescriptors } from '../../deviceDescriptors';
 
-export class PlaywrightDispatcher extends Dispatcher<Playwright, PlaywrightInitializer> implements PlaywrightChannel {
+export class PlaywrightDispatcher extends Dispatcher<Playwright, channels.PlaywrightInitializer> implements channels.PlaywrightChannel {
   constructor(scope: DispatcherScope, playwright: Playwright) {
     const electron = (playwright as any).electron as (Electron | undefined);
     const deviceDescriptors = Object.entries(DeviceDescriptors)
diff --git a/src/rpc/server/selectorsDispatcher.ts b/src/rpc/server/selectorsDispatcher.ts
index f15c2536cd..3d291b3c04 100644
--- a/src/rpc/server/selectorsDispatcher.ts
+++ b/src/rpc/server/selectorsDispatcher.ts
@@ -15,21 +15,21 @@
  */
 
 import { Dispatcher, DispatcherScope } from './dispatcher';
-import { SelectorsInitializer, SelectorsChannel } from '../channels';
+import * as channels from '../channels';
 import { Selectors } from '../../selectors';
 import { ElementHandleDispatcher } from './elementHandlerDispatcher';
 import * as dom from '../../dom';
 
-export class SelectorsDispatcher extends Dispatcher<Selectors, SelectorsInitializer> implements SelectorsChannel {
+export class SelectorsDispatcher extends Dispatcher<Selectors, channels.SelectorsInitializer> implements channels.SelectorsChannel {
   constructor(scope: DispatcherScope, selectors: Selectors) {
     super(scope, selectors, 'Selectors', {});
   }
 
-  async register(params: { name: string, source: string, contentScript?: boolean }): Promise<void> {
+  async register(params: channels.SelectorsRegisterParams): Promise<void> {
     await this._object.register(params.name, params.source, params.contentScript);
   }
 
-  async createSelector(params: { name: string, handle: ElementHandleDispatcher }): Promise<{ value?: string }> {
-    return { value: await this._object._createSelector(params.name, params.handle._object as dom.ElementHandle<Element>) };
+  async createSelector(params: channels.SelectorsCreateSelectorParams): Promise<channels.SelectorsCreateSelectorResult> {
+    return { value: await this._object._createSelector(params.name, (params.handle as ElementHandleDispatcher)._object as dom.ElementHandle<Element>) };
   }
 }
diff --git a/src/rpc/server/streamDispatcher.ts b/src/rpc/server/streamDispatcher.ts
index dd9acc3a60..dc28f08abf 100644
--- a/src/rpc/server/streamDispatcher.ts
+++ b/src/rpc/server/streamDispatcher.ts
@@ -14,16 +14,16 @@
  * limitations under the License.
  */
 
-import { StreamChannel, StreamInitializer, Binary } from '../channels';
+import * as channels from '../channels';
 import { Dispatcher, DispatcherScope } from './dispatcher';
 import * as stream from 'stream';
 
-export class StreamDispatcher extends Dispatcher<stream.Readable, StreamInitializer> implements StreamChannel {
+export class StreamDispatcher extends Dispatcher<stream.Readable, channels.StreamInitializer> implements channels.StreamChannel {
   constructor(scope: DispatcherScope, stream: stream.Readable) {
     super(scope, stream, 'Stream', {});
   }
 
-  async read(params: { size?: number }): Promise<{ binary: Binary }> {
+  async read(params: channels.StreamReadParams): Promise<channels.StreamReadResult> {
     const buffer = this._object.read(Math.min(this._object.readableLength, params.size || this._object.readableLength));
     return { binary: buffer ? buffer.toString('base64') : '' };
   }