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chore(webkit): use async/await to make eval more readable #789

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merged 2 commits into from
Feb 1, 2020
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chore(webkit): use async/await to make eval more readable #789

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5852889
chore(webkit): use async/await to make eval more readable
yury-s Jan 31, 2020
b8d6b4b
fields cleanup
yury-s Jan 31, 2020
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172 changes: 72 additions & 100 deletions src/webkit/wkExecutionContext.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -25,15 +25,14 @@ export const EVALUATION_SCRIPT_URL = '__playwright_evaluation_script__';
const SOURCE_URL_REGEX = /^[\040\t]*\/\/[@#] sourceURL=\s*(\S*?)\s*$/m;

export class WKExecutionContext implements js.ExecutionContextDelegate {
private _globalObjectId?: Promise<string>;
_session: WKSession;
_contextId: number | undefined;
private _globalObjectIdPromise?: Promise<Protocol.Runtime.RemoteObjectId>;
private readonly _session: WKSession;
readonly _contextId: number | undefined;
private _contextDestroyedCallback: () => void = () => {};
private _executionContextDestroyedPromise: Promise<unknown>;
_jsonStringifyObjectId: Protocol.Runtime.RemoteObjectId | undefined;
private readonly _executionContextDestroyedPromise: Promise<unknown>;

constructor(client: WKSession, contextId: number | undefined) {
this._session = client;
constructor(session: WKSession, contextId: number | undefined) {
this._session = session;
this._contextId = contextId;
this._executionContextDestroyedPromise = new Promise((resolve, reject) => {
this._contextDestroyedCallback = resolve;
Expand All @@ -45,37 +44,65 @@ export class WKExecutionContext implements js.ExecutionContextDelegate {
}

async evaluate(context: js.ExecutionContext, returnByValue: boolean, pageFunction: Function | string, ...args: any[]): Promise<any> {
try {
let response = await this._evaluateRemoteObject(pageFunction, args);
if (response.result.type === 'object' && response.result.className === 'Promise') {
response = await Promise.race([
this._executionContextDestroyedPromise.then(() => contextDestroyedResult),
this._session.send('Runtime.awaitPromise', {
promiseObjectId: response.result.objectId,
returnByValue: false
})
]);
}
if (response.wasThrown)
throw new Error('Evaluation failed: ' + response.result.description);
if (!returnByValue)
return context._createHandle(response.result);
if (response.result.objectId)
return await this._returnObjectByValue(response.result.objectId);
return valueFromRemoteObject(response.result);
} catch (error) {
if (isSwappedOutError(error) || error.message.includes('Missing injected script for given'))
throw new Error('Execution context was destroyed, most likely because of a navigation.');
throw error;
}
}

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 expressionWithSourceUrl = SOURCE_URL_REGEX.test(expression) ? expression : expression + '\n' + suffix;
return this._session.send('Runtime.evaluate', {
return await this._session.send('Runtime.evaluate', {
expression: expressionWithSourceUrl,
contextId,
returnByValue: false,
emulateUserGesture: true
}).then(response => {
if (response.result.type === 'object' && response.result.className === 'Promise') {
return Promise.race([
this._executionContextDestroyedPromise.then(() => contextDestroyedResult),
this._awaitPromise(response.result.objectId!),
]);
}
return response;
}).then(response => {
if (response.wasThrown)
throw new Error('Evaluation failed: ' + response.result.description);
if (!returnByValue)
return context._createHandle(response.result);
if (response.result.objectId)
return this._returnObjectByValue(response.result.objectId);
return valueFromRemoteObject(response.result);
}).catch(rewriteError);
});
}

if (typeof pageFunction !== 'function')
throw new Error(`Expected to get |string| or |function| as the first argument, but got "${pageFunction}" instead.`);

try {
const callParams = this._serializeFunctionAndArguments(pageFunction, args);
const thisObjectId = await this._contextGlobalObjectId();
return await this._session.send('Runtime.callFunctionOn', {
functionDeclaration: callParams.functionText + '\n' + suffix + '\n',
objectId: thisObjectId,
arguments: callParams.callArguments,
returnByValue: false,
emulateUserGesture: true
});
} catch (err) {
if (err instanceof TypeError && err.message.startsWith('Converting circular structure to JSON'))
err.message += ' Are you passing a nested JSHandle?';
throw err;
}
}

private _serializeFunctionAndArguments(pageFunction: Function, args: any[]): { functionText: string, callArguments: Protocol.Runtime.CallArgument[] } {
let functionText = pageFunction.toString();
try {
new Function('(' + functionText + ')');
Expand Down Expand Up @@ -110,43 +137,8 @@ export class WKExecutionContext implements js.ExecutionContextDelegate {
} else {
serializableArgs = args;
}

let thisObjectId;
try {
thisObjectId = await this._contextGlobalObjectId();
} catch (error) {
if (error.message.includes('Missing injected script for given'))
throw new Error('Execution context was destroyed, most likely because of a navigation.');
throw error;
}

return this._session.send('Runtime.callFunctionOn', {
functionDeclaration: functionText + '\n' + suffix + '\n',
objectId: thisObjectId,
arguments: serializableArgs.map((arg: any) => this._convertArgument(arg)),
returnByValue: false,
emulateUserGesture: true
}).catch(err => {
if (err instanceof TypeError && err.message.startsWith('Converting circular structure to JSON'))
err.message += ' Are you passing a nested JSHandle?';
throw err;
}).then(response => {
if (response.result.type === 'object' && response.result.className === 'Promise') {
return Promise.race([
this._executionContextDestroyedPromise.then(() => contextDestroyedResult),
this._awaitPromise(response.result.objectId!),
]);
}
return response;
}).then(response => {
if (response.wasThrown)
throw new Error('Evaluation failed: ' + response.result.description);
if (!returnByValue)
return context._createHandle(response.result);
if (response.result.objectId)
return this._returnObjectByValue(response.result.objectId).catch(() => undefined);
return valueFromRemoteObject(response.result);
}).catch(rewriteError);
const serialized = serializableArgs.map((arg: any) => this._convertArgument(arg));
return { functionText, callArguments: serialized };

function unserializableToString(arg: any) {
if (Object.is(arg, -0))
Expand Down Expand Up @@ -183,56 +175,36 @@ export class WKExecutionContext implements js.ExecutionContextDelegate {
}
return false;
}

function rewriteError(error: Error): Protocol.Runtime.evaluateReturnValue {
if (error.message.includes('Missing injected script for given'))
throw new Error('Execution context was destroyed, most likely because of a navigation.');
throw error;
}
}

private _contextGlobalObjectId() {
if (!this._globalObjectId) {
this._globalObjectId = this._session.send('Runtime.evaluate', {
private _contextGlobalObjectId() : Promise<Protocol.Runtime.RemoteObjectId> {
if (!this._globalObjectIdPromise) {
this._globalObjectIdPromise = this._session.send('Runtime.evaluate', {
expression: 'this',
contextId: this._contextId
}).catch(e => {
if (isSwappedOutError(e))
throw new Error('Execution context was destroyed, most likely because of a navigation.');
throw e;
}).then(response => {
return response.result.objectId!;
});
}
return this._globalObjectId;
return this._globalObjectIdPromise;
}

private _awaitPromise(objectId: Protocol.Runtime.RemoteObjectId) {
return this._session.send('Runtime.awaitPromise', {
promiseObjectId: objectId,
returnByValue: false
}).catch(e => {
if (isSwappedOutError(e))
return contextDestroyedResult;
throw e;
});
}

private _returnObjectByValue(objectId: Protocol.Runtime.RemoteObjectId) {
return this._session.send('Runtime.callFunctionOn', {
// Serialize object using standard JSON implementation to correctly pass 'undefined'.
functionDeclaration: 'function(){return this}\n' + suffix + '\n',
objectId: objectId,
returnByValue: true
}).catch(e => {
if (isSwappedOutError(e))
return contextDestroyedResult;
throw e;
}).then(serializeResponse => {
private async _returnObjectByValue(objectId: Protocol.Runtime.RemoteObjectId) : Promise<any> {
try {
const serializeResponse = await this._session.send('Runtime.callFunctionOn', {
// Serialize object using standard JSON implementation to correctly pass 'undefined'.
functionDeclaration: 'function(){return this}\n' + suffix + '\n',
objectId: objectId,
returnByValue: true
});
if (serializeResponse.wasThrown)
throw new Error('Serialization failed: ' + serializeResponse.result.description);
return undefined;
return serializeResponse.result.value;
});
} catch (e) {
if (isSwappedOutError(e))
return contextDestroyedResult;
return undefined;
}
}

async getProperties(handle: js.JSHandle): Promise<Map<string, js.JSHandle>> {
Expand Down