1 files changed, 188 insertions, 0 deletions
diff --git a/devtools/server/actors/tracer.js b/devtools/server/actors/tracer.js
new file mode 100644
index 0000000000..2c213f155c
--- /dev/null
+++ b/devtools/server/actors/tracer.js
@@ -0,0 +1,188 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+// Bug 1827382, as this module can be used from the worker thread,
+// the following JSM may be loaded by the worker loader until
+// we have proper support for ESM from workers.
+const {
+  startTracing,
+  stopTracing,
+  addTracingListener,
+  removeTracingListener,
+} = require("resource://devtools/server/tracer/tracer.jsm");
+
+const { Actor } = require("resource://devtools/shared/protocol.js");
+const { tracerSpec } = require("resource://devtools/shared/specs/tracer.js");
+
+const { throttle } = require("resource://devtools/shared/throttle.js");
+
+const {
+  TYPES,
+  getResourceWatcher,
+} = require("resource://devtools/server/actors/resources/index.js");
+
+const LOG_METHODS = {
+  STDOUT: "stdout",
+  CONSOLE: "console",
+};
+
+const CONSOLE_ARGS_STYLES = [
+  "color: var(--theme-toolbarbutton-checked-hover-background)",
+  "padding-inline: 4px; margin-inline: 2px; background-color: var(--theme-toolbarbutton-checked-hover-background); color: var(--theme-toolbarbutton-checked-hover-color);",
+  "",
+  "color: var(--theme-highlight-blue); margin-inline: 2px;",
+];
+
+const CONSOLE_THROTTLING_DELAY = 250;
+
+class TracerActor extends Actor {
+  constructor(conn, targetActor) {
+    super(conn, tracerSpec);
+    this.targetActor = targetActor;
+    this.sourcesManager = this.targetActor.sourcesManager;
+
+    // Flag used by CONSOLE_MESSAGE resources
+    this.isChromeContext = /conn\d+\.parentProcessTarget\d+/.test(
+      this.targetActor.actorID
+    );
+
+    this.throttledConsoleMessages = [];
+    this.throttleLogMessages = throttle(
+      this.flushConsoleMessages.bind(this),
+      CONSOLE_THROTTLING_DELAY
+    );
+  }
+
+  destroy() {
+    this.stopTracing();
+  }
+
+  getLogMethod() {
+    return this.logMethod;
+  }
+
+  startTracing(logMethod = LOG_METHODS.STDOUT) {
+    this.logMethod = logMethod;
+    this.tracingListener = {
+      onTracingFrame: this.onTracingFrame.bind(this),
+      onTracingInfiniteLoop: this.onTracingInfiniteLoop.bind(this),
+    };
+    addTracingListener(this.tracingListener);
+    startTracing({
+      global: this.targetActor.window || this.targetActor.workerGlobal,
+    });
+  }
+
+  stopTracing() {
+    if (!this.tracingListener) {
+      return;
+    }
+    stopTracing();
+    removeTracingListener(this.tracingListener);
+    this.logMethod = null;
+    this.tracingListener = null;
+  }
+
+  onTracingInfiniteLoop() {
+    if (this.logMethod == LOG_METHODS.STDOUT) {
+      return true;
+    }
+    const consoleMessageWatcher = getResourceWatcher(
+      this.targetActor,
+      TYPES.CONSOLE_MESSAGE
+    );
+    if (!consoleMessageWatcher) {
+      return true;
+    }
+
+    const message =
+      "Looks like an infinite recursion? We stopped the JavaScript tracer, but code may still be running!";
+    consoleMessageWatcher.emitMessages([
+      {
+        arguments: [message],
+        styles: [],
+        level: "logTrace",
+        chromeContext: this.isChromeContext,
+        timeStamp: ChromeUtils.dateNow(),
+      },
+    ]);
+
+    return false;
+  }
+
+  /**
+   * Called by JavaScriptTracer class when a new JavaScript frame is executed.
+   *
+   * @param {Debugger.Frame} frame
+   *        A descriptor object for the JavaScript frame.
+   * @param {Number} depth
+   *        Represents the depth of the frame in the call stack.
+   * @param {String} formatedDisplayName
+   *        A human readable name for the current frame.
+   * @param {String} prefix
+   *        A string to be displayed as a prefix of any logged frame.
+   * @return {Boolean}
+   *         Return true, if the JavaScriptTracer should log the frame to stdout.
+   */
+  onTracingFrame({ frame, depth, formatedDisplayName, prefix }) {
+    const { script } = frame;
+    const { lineNumber, columnNumber } = script.getOffsetMetadata(frame.offset);
+    const url = script.source.url;
+
+    // Ignore blackboxed sources
+    if (this.sourcesManager.isBlackBoxed(url, lineNumber, columnNumber)) {
+      return false;
+    }
+
+    if (this.logMethod == LOG_METHODS.STDOUT) {
+      // By returning true, we let JavaScriptTracer class log the message to stdout.
+      return true;
+    }
+
+    const args = [
+      prefix + "—".repeat(depth + 1),
+      frame.implementation,
+      "⟶",
+      formatedDisplayName,
+    ];
+
+    // Create a message object that fits Console Message Watcher expectations
+    this.throttledConsoleMessages.push({
+      filename: url,
+      lineNumber,
+      columnNumber,
+      arguments: args,
+      styles: CONSOLE_ARGS_STYLES,
+      level: "logTrace",
+      chromeContext: this.isChromeContext,
+      sourceId: script.source.id,
+      timeStamp: ChromeUtils.dateNow(),
+    });
+    this.throttleLogMessages();
+
+    return false;
+  }
+
+  /**
+   * This method is throttled and will notify all pending traces to be logged in the console
+   * via the console message watcher.
+   */
+  flushConsoleMessages() {
+    const consoleMessageWatcher = getResourceWatcher(
+      this.targetActor,
+      TYPES.CONSOLE_MESSAGE
+    );
+    // Ignore the request if the frontend isn't listening to console messages for that target.
+    if (!consoleMessageWatcher) {
+      return;
+    }
+    const messages = this.throttledConsoleMessages;
+    this.throttledConsoleMessages = [];
+
+    consoleMessageWatcher.emitMessages(messages);
+  }
+}
+exports.TracerActor = TracerActor;