chore(lint): add @typescript-eslint/no-unnecessary-type-assertion rule (#898)

.eslintrc.js

@@ -106,6 +106,9 @@ module.exports = {
         "indent": [2, 2, { "SwitchCase": 1, "CallExpression": {"arguments": 2}, "MemberExpression": 2 }],
         "key-spacing": [2, {
             "beforeColon": false
-        }]
+        }],
+
+        // type-aware rules
+        "@typescript-eslint/no-unnecessary-type-assertion": 2,
     }
 };

src/chromium/crBrowser.ts

@@ -287,7 +287,7 @@ export class CRBrowser extends platform.EventEmitter implements Browser {
     this._tracingClient.once('Tracing.tracingComplete', event => {
       readProtocolStream(this._tracingClient!, event.stream!, this._tracingPath).then(fulfill);
     });
-    await this._tracingClient!.send('Tracing.end');
+    await this._tracingClient.send('Tracing.end');
     this._tracingRecording = false;
     return contentPromise;
   }

src/chromium/crExecutionContext.ts

@@ -38,7 +38,7 @@ export class CRExecutionContext implements js.ExecutionContextDelegate {
 
     if (helper.isString(pageFunction)) {
       const contextId = this._contextId;
-      const expression: string = pageFunction as string;
+      const expression: string = pageFunction;
       const expressionWithSourceUrl = SOURCE_URL_REGEX.test(expression) ? expression : expression + '\n' + suffix;
       const {exceptionDetails, result: remoteObject} = await this._client.send('Runtime.evaluate', {
         expression: expressionWithSourceUrl,

src/chromium/crPage.ts

@@ -282,12 +282,12 @@ export class CRPage implements PageDelegate {
 
   _onDialog(event: Protocol.Page.javascriptDialogOpeningPayload) {
     this._page.emit(Events.Page.Dialog, new dialog.Dialog(
-      event.type as dialog.DialogType,
+        event.type,
-      event.message,
+        event.message,
-      async (accept: boolean, promptText?: string) => {
+        async (accept: boolean, promptText?: string) => {
-        await this._client.send('Page.handleJavaScriptDialog', { accept, promptText });
+          await this._client.send('Page.handleJavaScriptDialog', { accept, promptText });
-      },
+        },
-      event.defaultPrompt));
+        event.defaultPrompt));
   }
 
   _handleException(exceptionDetails: Protocol.Runtime.ExceptionDetails) {

src/chromium/crPdf.ts

@@ -48,9 +48,9 @@ function convertPrintParameterToInches(parameter: (string | number | undefined))
   let pixels: number;
   if (helper.isNumber(parameter)) {
     // Treat numbers as pixel values to be aligned with phantom's paperSize.
-    pixels = parameter as number;
+    pixels = parameter;
   } else if (helper.isString(parameter)) {
-    const text: string = parameter as string;
+    const text: string = parameter;
     let unit = text.substring(text.length - 2).toLowerCase();
     let valueText = '';
     if (unitToPixels.hasOwnProperty(unit)) {

src/firefox/ffPage.ts

@@ -119,7 +119,7 @@ export class FFPage implements PageDelegate {
     if (!context)
       return;
     this._contextIdToContext.delete(executionContextId);
-    context.frame._contextDestroyed(context as dom.FrameExecutionContext);
+    context.frame._contextDestroyed(context);
   }
 
   private _removeContextsForFrame(frame: frames.Frame) {
@@ -180,12 +180,12 @@ export class FFPage implements PageDelegate {
 
   _onDialogOpened(params: Protocol.Page.dialogOpenedPayload) {
     this._page.emit(Events.Page.Dialog, new dialog.Dialog(
-      params.type as dialog.DialogType,
+        params.type,
-      params.message,
+        params.message,
-      async (accept: boolean, promptText?: string) => {
+        async (accept: boolean, promptText?: string) => {
-        await this._session.send('Page.handleDialog', { dialogId: params.dialogId, accept, promptText }).catch(debugError);
+          await this._session.send('Page.handleDialog', { dialogId: params.dialogId, accept, promptText }).catch(debugError);
-      },
+        },
-      params.defaultValue));
+        params.defaultValue));
   }
 
   _onBindingCalled(event: Protocol.Page.bindingCalledPayload) {

src/frames.ts

@@ -767,9 +767,9 @@ export class Frame {
 
   async waitFor(selectorOrFunctionOrTimeout: (string | number | Function), options: types.WaitForFunctionOptions & { visibility?: types.Visibility } = {}, ...args: any[]): Promise<js.JSHandle | null> {
     if (helper.isString(selectorOrFunctionOrTimeout))
-      return this.waitForSelector(selectorOrFunctionOrTimeout as string, options) as any;
+      return this.waitForSelector(selectorOrFunctionOrTimeout, options) as any;
     if (helper.isNumber(selectorOrFunctionOrTimeout))
-      return new Promise(fulfill => setTimeout(fulfill, selectorOrFunctionOrTimeout as number));
+      return new Promise(fulfill => setTimeout(fulfill, selectorOrFunctionOrTimeout));
     if (typeof selectorOrFunctionOrTimeout === 'function')
       return this.waitForFunction(selectorOrFunctionOrTimeout, options, ...args);
     return Promise.reject(new Error('Unsupported target type: ' + (typeof selectorOrFunctionOrTimeout)));

src/helper.ts

@@ -30,7 +30,7 @@ class Helper {
   static evaluationString(fun: Function | string, ...args: any[]): string {
     if (Helper.isString(fun)) {
       assert(args.length === 0, 'Cannot evaluate a string with arguments');
-      return fun as string;
+      return fun;
     }
     return `(${fun})(${args.map(serializeArgument).join(',')})`;
 

src/injected/cssSelectorEngine.ts

@@ -64,7 +64,7 @@ export const CSSEngine: SelectorEngine = {
       // Ordinal is the weakest signal.
       if (parent) {
         const siblings = Array.from(parent.children);
-        const sameTagSiblings = siblings.filter(sibling => (sibling as Element).nodeName.toLowerCase() === nodeName);
+        const sameTagSiblings = siblings.filter(sibling => (sibling).nodeName.toLowerCase() === nodeName);
         const token = sameTagSiblings.length === 1 ? nodeName : `${nodeName}:nth-child(${1 + siblings.indexOf(element)})`;
         const selector = uniqueCSSSelector(token);
         if (selector)

src/injected/xpathSelectorEngine.ts

@@ -26,7 +26,7 @@ export const XPathEngine: SelectorEngine = {
     const maybeDocument = root instanceof Document ? root : root.ownerDocument;
     if (!maybeDocument)
       return;
-    const document = maybeDocument!;
+    const document = maybeDocument;
 
     const xpathCache = new Map<string, Element[]>();
     if (type === 'notext')
@@ -135,7 +135,7 @@ export const XPathEngine: SelectorEngine = {
       let tagWithOrdinal = tag;
       if (parent) {
         const siblings = Array.from(parent.children);
-        const sameTagSiblings = siblings.filter(sibling => (sibling as Element).nodeName.toLowerCase() === nodeName);
+        const sameTagSiblings = siblings.filter(sibling => (sibling).nodeName.toLowerCase() === nodeName);
         if (sameTagSiblings.length > 1)
           tagWithOrdinal += `[${1 + siblings.indexOf(element)}]`;
       }

src/injected/zsSelectorEngine.ts

@@ -780,9 +780,9 @@ const ZSSelectorEngine: SelectorEngine = {
     while (e && e.namespaceURI && e.namespaceURI.endsWith('svg') && e.nodeName.toLowerCase() !== 'svg')
       e = e.parentElement!;
     try {
-      document.documentElement!.style!.outline = '1px solid red';
+      document.documentElement.style.outline = '1px solid red';
       const selector = new Engine().create(document.documentElement, e, 'default');
-      document.documentElement!.style!.outline = '1px solid green';
+      document.documentElement.style.outline = '1px solid green';
       const e2 = new Engine().query(document.documentElement, selector, false)[0];
       return e !== e2;
     } catch (e) {

src/screenshotter.ts

@@ -100,7 +100,7 @@ export class Screenshotter {
 
       let maybeBoundingBox = await this._page._delegate.getBoundingBoxForScreenshot(handle);
       assert(maybeBoundingBox, 'Node is either not visible or not an HTMLElement');
-      let boundingBox = maybeBoundingBox!;
+      let boundingBox = maybeBoundingBox;
       assert(boundingBox.width !== 0, 'Node has 0 width.');
       assert(boundingBox.height !== 0, 'Node has 0 height.');
       boundingBox = enclosingIntRect(boundingBox);
@@ -118,7 +118,7 @@ export class Screenshotter {
           });
           if (!maybeViewportSize)
             throw new Error(kScreenshotDuringNavigationError);
-          viewportSize = maybeViewportSize!;
+          viewportSize = maybeViewportSize;
         } else {
           viewportSize = originalViewportSize;
         }
@@ -133,7 +133,7 @@ export class Screenshotter {
         await handle.scrollIntoViewIfNeeded();
         maybeBoundingBox = await this._page._delegate.getBoundingBoxForScreenshot(handle);
         assert(maybeBoundingBox, 'Node is either not visible or not an HTMLElement');
-        boundingBox = enclosingIntRect(maybeBoundingBox!);
+        boundingBox = enclosingIntRect(maybeBoundingBox);
       }
 
       if (!overridenViewportSize)

src/server/webkit.ts

@@ -337,7 +337,7 @@ function wrapTransportWithWebSocket(transport: ConnectionTransport, port: number
     if (method === 'Browser.provisionalLoadFailed') {
       const socket = pageProxyIds.get(params.pageProxyId);
       if (socket && socket.readyState !== ws.CLOSING)
-        socket!.send(message);
+        socket.send(message);
       return;
     }
   };

src/webkit/wkBrowser.ts

@@ -197,8 +197,8 @@ export class WKBrowser extends platform.EventEmitter implements Browser {
 
       close: async (): Promise<void> => {
         assert(browserContextId, 'Non-incognito profiles cannot be closed!');
-        await this._browserSession.send('Browser.deleteContext', { browserContextId: browserContextId! });
+        await this._browserSession.send('Browser.deleteContext', { browserContextId: browserContextId });
-        this._contexts.delete(browserContextId!);
+        this._contexts.delete(browserContextId);
       },
 
       cookies: async (): Promise<network.NetworkCookie[]> => {

src/webkit/wkExecutionContext.ts

@@ -72,7 +72,7 @@ export class WKExecutionContext implements js.ExecutionContextDelegate {
   private async _evaluateRemoteObject(pageFunction: Function | string, args: any[]): Promise<any> {
     if (helper.isString(pageFunction)) {
       const contextId = this._contextId;
-      const expression: string = pageFunction as string;
+      const expression: string = pageFunction;
       const expressionWithSourceUrl = SOURCE_URL_REGEX.test(expression) ? expression : expression + '\n' + suffix;
       return await this._session.send('Runtime.evaluate', {
         expression: expressionWithSourceUrl,

src/webkit/wkPage.ts

@@ -156,9 +156,9 @@ export class WKPage implements PageDelegate {
 
   onProvisionalLoadCommitted(session: WKSession) {
     assert(this._provisionalPage);
-    assert(this._provisionalPage!._session === session);
+    assert(this._provisionalPage._session === session);
-    this._provisionalPage!.commit();
+    this._provisionalPage.commit();
-    this._provisionalPage!.dispose();
+    this._provisionalPage.dispose();
     this._provisionalPage = null;
     this._setSession(session);
   }
@@ -260,7 +260,7 @@ export class WKPage implements PageDelegate {
   private _onFrameNavigated(framePayload: Protocol.Page.Frame, initial: boolean) {
     const frame = this._page._frameManager.frame(framePayload.id);
     assert(frame);
-    this._removeContextsForFrame(frame!, true);
+    this._removeContextsForFrame(frame, true);
     if (!framePayload.parentId)
       this._workers.clear();
     this._page._frameManager.frameCommittedNewDocumentNavigation(framePayload.id, framePayload.url, framePayload.name || '', framePayload.loaderId, initial);
@@ -306,7 +306,7 @@ export class WKPage implements PageDelegate {
     if (this._pageProxySession.isDisposed())
       throw new Error('Target closed');
     const pageProxyId = this._pageProxySession.sessionId;
-    const result = await this._pageProxySession.connection!.browserSession.send('Browser.navigate', { url, pageProxyId, frameId: frame._id, referrer });
+    const result = await this._pageProxySession.connection.browserSession.send('Browser.navigate', { url, pageProxyId, frameId: frame._id, referrer });
     return { newDocumentId: result.loaderId, isSameDocument: !result.loaderId };
   }
 

src/webkit/wkPageProxy.ts

@@ -119,9 +119,9 @@ export class WKPageProxy {
         return null;
       return await pageProxy.page();
     });
-    await this._wkPage.initialize(session!);
+    await this._wkPage.initialize(session);
     if (this._pagePausedOnStart) {
-      this._resumeTarget(session!.sessionId);
+      this._resumeTarget(session.sessionId);
       this._pagePausedOnStart = false;
     }
     return this._wkPage._page;
@@ -169,17 +169,17 @@ export class WKPageProxy {
     const { targetId, crashed } = event;
     const session = this._sessions.get(targetId);
     assert(session, 'Unknown target destroyed: ' + targetId);
-    session!.dispose();
+    session.dispose();
     this._sessions.delete(targetId);
     if (this._wkPage)
-      this._wkPage.onSessionDestroyed(session!, crashed);
+      this._wkPage.onSessionDestroyed(session, crashed);
   }
 
   private _onDispatchMessageFromTarget(event: Protocol.Target.dispatchMessageFromTargetPayload) {
     const { targetId, message } = event;
     const session = this._sessions.get(targetId);
     assert(session, 'Unknown target: ' + targetId);
-    session!.dispatchMessage(JSON.parse(message));
+    session.dispatchMessage(JSON.parse(message));
   }
 
   private _onDidCommitProvisionalTarget(event: Protocol.Target.didCommitProvisionalTargetPayload) {
@@ -189,9 +189,9 @@ export class WKPageProxy {
     const oldSession = this._sessions.get(oldTargetId);
     assert(oldSession, 'Unknown old target: ' + oldTargetId);
     // TODO: make some calls like screenshot catch swapped out error and retry.
-    oldSession!.errorText = 'Target was swapped out.';
+    oldSession.errorText = 'Target was swapped out.';
     (newSession as any)[isPovisionalSymbol] = undefined;
     if (this._wkPage)
-      this._wkPage.onProvisionalLoadCommitted(newSession!);
+      this._wkPage.onProvisionalLoadCommitted(newSession);
   }
 }

src/webkit/wkProvisionalPage.ts

@@ -57,7 +57,7 @@ export class WKProvisionalPage {
 
   commit() {
     assert(this._mainFrameId);
-    this._wkPage._onFrameAttached(this._mainFrameId!, null);
+    this._wkPage._onFrameAttached(this._mainFrameId, null);
   }
 
   private _handleFrameTree(frameTree: Protocol.Page.FrameResourceTree) {