Bug 1819767 - [devtools] Expose ChromeUtils.isDevToolsOpened to know if DevTools are debugging something in the current process. r=smaug,devtools-reviewers,jdescottes

This doesn't help know what particular resource DevTools is currently inspecting,
but at least it helps know if it debugs something:
* one or many BrowsingContext(s) for regular DevTools (you can use BrowsingContext.watchedByDevTools instead)
* the whole process for the Browser Console/Toolbox

Differential Revision: https://phabricator.services.mozilla.com/D173295

devtools/server/devtools-server.js

@@ -394,6 +394,12 @@ var DevToolsServer = {
       connID = "server" + loader.id + ".conn" + this._nextConnID++ + ".";
     }
 
+    // Notify the platform code that DevTools is running in the current process
+    // when we are wiring the very first connection
+    if (!this.hasConnection()) {
+      ChromeUtils.notifyDevToolsOpened();
+    }
+
     const conn = new DevToolsServerConnection(
       connID,
       transport,
@@ -425,13 +431,20 @@ var DevToolsServer = {
     delete this._connections[connection.prefix];
     this.emit("connectionchange", "closed", connection);
 
+    const hasConnection = this.hasConnection();
+
+    // Notify the platform code that we stopped running DevTools code in the current process
+    if (!hasConnection) {
+      ChromeUtils.notifyDevToolsClosed();
+    }
+
     // If keepAlive isn't explicitely set to true, destroy the server once its
     // last connection closes. Multiple JSWindowActor may use the same DevToolsServer
     // and in this case, let the server destroy itself once the last connection closes.
     // Otherwise we set keepAlive to true when starting a listening server, receiving
     // client connections. Typically when running server on phones, or on desktop
     // via `--start-debugger-server`.
-    if (this.hasConnection() || this.keepAlive) {
+    if (hasConnection || this.keepAlive) {
       return;
     }
 

devtools/server/tests/browser/browser_debugger_server.js

@@ -28,6 +28,11 @@ async function testDevToolsServerInitialized() {
     false,
     "By default, the DevToolsServer isn't initialized not in content process"
   );
+  await assertDevToolsOpened(
+    tab,
+    false,
+    "By default, the DevTools are reported as closed"
+  );
 
   const commands = await CommandsFactory.forTab(tab);
 
@@ -40,6 +45,11 @@ async function testDevToolsServerInitialized() {
     false,
     "Creating the commands isn't enough to initialize the DevToolsServer in content process"
   );
+  await assertDevToolsOpened(
+    tab,
+    false,
+    "DevTools are still reported as closed after having created the commands"
+  );
 
   await commands.targetCommand.startListening();
 
@@ -48,6 +58,11 @@ async function testDevToolsServerInitialized() {
     true,
     "Initializing the TargetCommand will initialize the DevToolsServer in content process"
   );
+  await assertDevToolsOpened(
+    tab,
+    true,
+    "Initializing the TargetCommand will start reporting the DevTools as opened"
+  );
 
   await commands.destroy();
 
@@ -61,6 +76,11 @@ async function testDevToolsServerInitialized() {
     false,
     "But destroying the commands ends up destroying the DevToolsServer in the content process"
   );
+  await assertDevToolsOpened(
+    tab,
+    false,
+    "Destroying the commands will report DevTools as being closed"
+  );
 
   gBrowser.removeCurrentTab();
   DevToolsServer.destroy();
@@ -74,11 +94,13 @@ async function testDevToolsServerKeepAlive() {
     false,
     "Server not started in content process"
   );
+  await assertDevToolsOpened(tab, false, "DevTools are reported as closed");
 
   const commands = await CommandsFactory.forTab(tab);
   await commands.targetCommand.startListening();
 
   await assertServerInitialized(tab, true, "Server started in content process");
+  await assertDevToolsOpened(tab, true, "DevTools are reported as opened");
 
   info("Set DevToolsServer.keepAlive to true in the content process");
   DevToolsServer.keepAlive = true;
@@ -92,6 +114,11 @@ async function testDevToolsServerKeepAlive() {
     true,
     "Server still running in content process"
   );
+  await assertDevToolsOpened(
+    tab,
+    false,
+    "DevTools are reported as close, even if the server is still running because there is no more client connected"
+  );
 
   ok(
     DevToolsServer.initialized,
@@ -113,6 +140,11 @@ async function testDevToolsServerKeepAlive() {
     false,
     "Server stopped in content process"
   );
+  await assertDevToolsOpened(
+    tab,
+    false,
+    "DevTools are reported as closed after destroying the second commands"
+  );
 
   ok(
     !DevToolsServer.initialized,
@@ -124,20 +156,27 @@ async function testDevToolsServerKeepAlive() {
 }
 
 async function assertServerInitialized(tab, expected, message) {
-  const isInitialized = await SpecialPowers.spawn(
-    tab.linkedBrowser,
-    [],
-    function() {
+  await SpecialPowers.spawn(tab.linkedBrowser, [expected, message], function(
+    _expected,
+    _message
+  ) {
     const { require } = ChromeUtils.importESModule(
       "resource://devtools/shared/loader/Loader.sys.mjs"
     );
     const {
       DevToolsServer,
     } = require("resource://devtools/server/devtools-server.js");
-      return DevToolsServer.initialized;
+    is(DevToolsServer.initialized, _expected, _message);
+  });
 }
-  );
-  is(isInitialized, expected, message);
+
+async function assertDevToolsOpened(tab, expected, message) {
+  await SpecialPowers.spawn(tab.linkedBrowser, [expected, message], function(
+    _expected,
+    _message
+  ) {
+    is(ChromeUtils.isDevToolsOpened(), _expected, _message);
+  });
 }
 
 async function setContentServerKeepAlive(tab, keepAlive, message) {

dom/base/ChromeUtils.cpp

@@ -1858,4 +1858,28 @@ void ChromeUtils::GetAllPossibleUtilityActorNames(GlobalObject& aGlobal,
     aNames.AppendElement(WebIDLUtilityActorNameValues::GetString(idlName));
   }
 }
+
+std::atomic<uint32_t> ChromeUtils::sDevToolsOpenedCount = 0;
+
+/* static */
+bool ChromeUtils::IsDevToolsOpened() {
+  return ChromeUtils::sDevToolsOpenedCount > 0;
+}
+
+/* static */
+bool ChromeUtils::IsDevToolsOpened(GlobalObject& aGlobal) {
+  return ChromeUtils::IsDevToolsOpened();
+}
+
+/* static */
+void ChromeUtils::NotifyDevToolsOpened(GlobalObject& aGlobal) {
+  ChromeUtils::sDevToolsOpenedCount++;
+}
+
+/* static */
+void ChromeUtils::NotifyDevToolsClosed(GlobalObject& aGlobal) {
+  MOZ_ASSERT(ChromeUtils::sDevToolsOpenedCount >= 1);
+  ChromeUtils::sDevToolsOpenedCount--;
+}
+
 }  // namespace mozilla::dom

dom/base/ChromeUtils.h

@@ -65,6 +65,11 @@ class ChromeUtils {
   static already_AddRefed<devtools::HeapSnapshot> ReadHeapSnapshot(
       GlobalObject& global, const nsAString& filePath, ErrorResult& rv);
 
+  static bool IsDevToolsOpened();
+  static bool IsDevToolsOpened(GlobalObject& aGlobal);
+  static void NotifyDevToolsOpened(GlobalObject& aGlobal);
+  static void NotifyDevToolsClosed(GlobalObject& aGlobal);
+
   static void NondeterministicGetWeakMapKeys(
       GlobalObject& aGlobal, JS::Handle<JS::Value> aMap,
       JS::MutableHandle<JS::Value> aRetval, ErrorResult& aRv);
@@ -296,6 +301,10 @@ class ChromeUtils {
 
   static void GetAllPossibleUtilityActorNames(GlobalObject& aGlobal,
                                               nsTArray<nsCString>& aNames);
+
+ private:
+  // Number of DevTools session debugging the current process
+  static std::atomic<uint32_t> sDevToolsOpenedCount;
 };
 
 }  // namespace dom

dom/chrome-webidl/ChromeUtils.webidl

@@ -115,6 +115,26 @@ namespace ChromeUtils {
   [Throws, NewObject]
   HeapSnapshot readHeapSnapshot(DOMString filePath);
 
+  /**
+   * Efficient way to know if DevTools are active in the current process.
+   *
+   * This doesn't help know what particular context is being debugged,
+   * but can help strip off code entirely when DevTools aren't used at all.
+   *
+   * BrowsingContext.isWatchedByDevTools is a more precise way to know
+   * when one precise tab is being debugged.
+   */
+  boolean isDevToolsOpened();
+
+  /**
+   * API exposed to DevTools JS code in order to know when devtools are being active in the current process.
+   *
+   * This API counts the number of calls to these methods, allowing to track many DevTools instances.
+   */
+  undefined notifyDevToolsOpened();
+  undefined notifyDevToolsClosed();
+
+
   /**
    * Return the keys in a weak map.  This operation is
    * non-deterministic because it is affected by the scheduling of the