DevTools: Give argument hints in the console prompt

https://i.imgur.com/Y3OlPM2.png

Change-Id: Ic1d9ef1d47ff93ce77bfc3ae7173689bccf0cb2c
Reviewed-on: https://chromium-review.googlesource.com/1031096
Reviewed-by: Andrey Lushnikov <lushnikov@chromium.org>
Commit-Queue: Joel Einbinder <einbinder@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#557030}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 66bdf19b13c9a1dffbd47121101e0b8aedde3495

front_end/object_ui/JavaScriptAutocomplete.js

@@ -32,6 +32,43 @@ ObjectUI.JavaScriptAutocomplete = class {
     return mapCompletions.concat(expressionCompletions);
   }
 
+  /**
+   * @param {string} fullText
+   * @return {!Promise<?{args: !Array<string>, argumentIndex: number}>}
+   */
+  async argumentsHint(fullText) {
+    const functionCall = await Formatter.formatterWorkerPool().findLastFunctionCall(fullText);
+    if (!functionCall)
+      return null;
+    const executionContext = UI.context.flavor(SDK.ExecutionContext);
+    if (!executionContext)
+      return null;
+    const result = await executionContext.evaluate(
+        {
+          expression: functionCall.baseExpression,
+          objectGroup: 'argumentsHint',
+          includeCommandLineAPI: true,
+          silent: true,
+          returnByValue: false,
+          generatePreview: false,
+          throwOnSideEffect: functionCall.possibleSideEffects,
+          timeout: functionCall.possibleSideEffects ? 500 : undefined
+        },
+        /* userGesture */ false, /* awaitPromise */ false);
+    if (!result || result.exceptionDetails || !result.object || result.object.type !== 'function')
+      return null;
+    executionContext.runtimeModel.releaseObjectGroup('argumentsHint');
+
+    const description = result.object.description;
+    if (description.endsWith('{ [native code] }'))
+      return null;  // TODO(einbinder) support native function argument hints
+    const args = await Formatter.formatterWorkerPool().argumentsList(description);
+
+    if (!args.length)
+      return null;
+    return {args, argumentIndex: functionCall.argumentIndex};
+  }
+
   /**
    * @param {string} text
    * @param {string} query