1 files changed, 143 insertions, 0 deletions
diff --git a/devtools/shared/test-helpers/thread-helpers.sys.mjs b/devtools/shared/test-helpers/thread-helpers.sys.mjs
new file mode 100644
index 0000000000..b99fc16f00
--- /dev/null
+++ b/devtools/shared/test-helpers/thread-helpers.sys.mjs
@@ -0,0 +1,143 @@
+/* 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/. */
+
+/**
+ * Helper code to play with the javascript thread
+ **/
+
+function getSandboxWithDebuggerSymbol() {
+  // Bug 1835268 - Changing this to an ES module import currently throws an
+  // assertion in test_javascript_tracer.js in debug builds.
+  const { addDebuggerToGlobal } = ChromeUtils.import(
+    "resource://gre/modules/jsdebugger.jsm"
+  );
+  const systemPrincipal = Services.scriptSecurityManager.getSystemPrincipal();
+
+  const debuggerSandbox = Cu.Sandbox(systemPrincipal, {
+    // This sandbox is also reused for ChromeDebugger implementation.
+    // As we want to load the `Debugger` API for debugging chrome contexts,
+    // we have to ensure loading it in a distinct compartment from its debuggee.
+    freshCompartment: true,
+    invisibleToDebugger: true,
+  });
+  addDebuggerToGlobal(debuggerSandbox);
+
+  return debuggerSandbox;
+}
+
+/**
+ * Implementation of a Javascript tracer logging traces to stdout.
+ *
+ * To be used like this:
+
+  const { traceAllJSCalls } = ChromeUtils.importESModule(
+    "resource://devtools/shared/test-helpers/thread-helpers.sys.mjs"
+  );
+  const jsTracer = traceAllJSCalls();
+  [... execute some code to tracer ...]
+  jsTracer.stop();
+
+ * @param prefix String
+ *        Optional, if passed, this will be displayed in front of each
+ *        line reporting a new frame execution.
+ * @param pause Number
+ *        Optional, if passed, hold off each frame for `pause` ms,
+ *        by letting the other event loops run in between.
+ *        Be careful that it can introduce unexpected race conditions
+ *        that can't necessarily be reproduced without this.
+ */
+export function traceAllJSCalls({ prefix = "", pause } = {}) {
+  const debuggerSandbox = getSandboxWithDebuggerSymbol();
+
+  debuggerSandbox.Services = Services;
+  const f = Cu.evalInSandbox(
+    "(" +
+      function (pauseInMs, prefixString) {
+        const dbg = new Debugger();
+        // Add absolutely all the globals...
+        dbg.addAllGlobalsAsDebuggees();
+        // ...but avoid tracing this sandbox code
+        const global = Cu.getGlobalForObject(this);
+        dbg.removeDebuggee(global);
+
+        // Add all globals created later on
+        dbg.onNewGlobalObject = g => dbg.addDebuggee(g);
+
+        function formatDisplayName(frame) {
+          if (frame.type === "call") {
+            const callee = frame.callee;
+            return callee.name || callee.userDisplayName || callee.displayName;
+          }
+
+          return `(${frame.type})`;
+        }
+
+        function stop() {
+          dbg.onEnterFrame = undefined;
+          dbg.removeAllDebuggees();
+        }
+        global.stop = stop;
+
+        let depth = 0;
+        dbg.onEnterFrame = frame => {
+          if (depth == 100) {
+            dump(
+              "Looks like an infinite loop? We stop the js tracer, but code may still be running!\n"
+            );
+            stop();
+            return;
+          }
+
+          const { script } = frame;
+          const { lineNumber, columnNumber } = script.getOffsetMetadata(
+            frame.offset
+          );
+          const padding = new Array(depth).join(" ");
+          dump(
+            `${prefixString}${padding}--[${frame.implementation}]--> ${
+              script.source.url
+            } @ ${lineNumber}:${columnNumber} - ${formatDisplayName(frame)}\n`
+          );
+
+          depth++;
+          frame.onPop = () => {
+            depth--;
+          };
+
+          // Optionaly pause the frame execute by letting the other event loop to run in between.
+          if (typeof pauseInMs == "number") {
+            let freeze = true;
+            const timer = Cc["@mozilla.org/timer;1"].createInstance(
+              Ci.nsITimer
+            );
+            timer.initWithCallback(
+              () => {
+                freeze = false;
+              },
+              pauseInMs,
+              Ci.nsITimer.TYPE_ONE_SHOT
+            );
+            Services.tm.spinEventLoopUntil("debugger-slow-motion", function () {
+              return !freeze;
+            });
+          }
+        };
+
+        return { stop };
+      } +
+      ")",
+    debuggerSandbox,
+    undefined,
+    "debugger-javascript-tracer",
+    1,
+    /* enforceFilenameRestrictions */ false
+  );
+  f(pause, prefix);
+
+  return {
+    stop() {
+      debuggerSandbox.stop();
+    },
+  };
+}