Bug 1398198 - browser_startup.js should show the stack when a JS file was loaded earlier than expected, r=felipe,mccr8.

browser/base/content/test/performance/browser.ini

@@ -1,4 +1,6 @@
 [DEFAULT]
+prefs =
+  browser.startup.record=true
 support-files =
   head.js
 [browser_appmenu_reflows.js]

browser/base/content/test/performance/browser_startup.js

@@ -16,6 +16,9 @@
 
 "use strict";
 
+/* Set this to true only for debugging purpose; it makes the output noisy. */
+const kDumpAllStacks = false;
+
 const startupPhases = {
   // For app-startup, we have a whitelist of acceptable JS files.
   // Anything loaded during app-startup must have a compelling reason
@@ -152,13 +155,25 @@ add_task(async function() {
   let startupRecorder = Cc["@mozilla.org/test/startuprecorder;1"].getService().wrappedJSObject;
   await startupRecorder.done;
 
+  let loader = Cc["@mozilla.org/moz/jsloader;1"].getService(Ci.xpcIJSModuleLoader);
+  let componentStacks = new Map();
   let data = startupRecorder.data.code;
   // Keep only the file name for components, as the path is an absolute file
   // URL rather than a resource:// URL like for modules.
   for (let phase in data) {
     data[phase].components =
-      data[phase].components.map(f => f.replace(/.*\//, ""))
-                            .filter(c => c != "startupRecorder.js");
+      data[phase].components.map(uri => {
+        let fileName = uri.replace(/.*\//, "");
+        componentStacks.set(fileName, loader.getComponentLoadStack(uri));
+        return fileName;
+      }).filter(c => c != "startupRecorder.js");
+  }
+
+  function printStack(scriptType, name) {
+    if (scriptType == "modules")
+      info(loader.getModuleImportStack(name));
+    else if (scriptType == "components")
+      info(componentStacks.get(name));
   }
 
   // This block only adds debug output to help find the next bugs to file,
@@ -171,8 +186,11 @@ add_task(async function() {
         // phases are ordered, so if a script wasn't loaded yet at the immediate
         // previous phase, it wasn't loaded during any of the previous phases
         // either, and is new in the current phase.
-        if (!previous || !data[previous][scriptType].includes(f))
+        if (!previous || !data[previous][scriptType].includes(f)) {
           info(`${scriptType} loaded ${phase}: ${f}`);
+          if (kDumpAllStacks)
+            printStack(scriptType, f);
+        }
       }
     }
     previous = phase;
@@ -193,6 +211,7 @@ add_task(async function() {
            `should have no unexpected ${scriptType} loaded ${phase}`);
         for (let script of loadedList[scriptType]) {
           ok(false, `unexpected ${scriptType}: ${script}`);
+          printStack(scriptType, script);
         }
         is(whitelist[scriptType].size, 0,
            `all ${scriptType} whitelist entries should have been used`);
@@ -205,7 +224,10 @@ add_task(async function() {
     if (blacklist) {
       for (let scriptType in blacklist) {
         for (let file of blacklist[scriptType]) {
-          ok(!loadedList[scriptType].includes(file), `${file} is not allowed ${phase}`);
+          let loaded = loadedList[scriptType].includes(file);
+          ok(!loaded, `${file} is not allowed ${phase}`);
+          if (loaded)
+            printStack(scriptType, file);
         }
       }
     }

browser/components/tests/startupRecorder.js

@@ -41,6 +41,9 @@ startupRecorder.prototype = {
   QueryInterface: XPCOMUtils.generateQI([Ci.nsIObserver]),
 
   record(name) {
+    if (!Services.prefs.getBoolPref("browser.startup.record", false))
+      return;
+
     this.data.code[name] = {
       components: this.loader.loadedComponents(),
       modules: this.loader.loadedModules(),
@@ -81,6 +84,12 @@ startupRecorder.prototype = {
     Services.obs.removeObserver(this, topic);
 
     if (topic == "sessionstore-windows-restored") {
+      if (!Services.prefs.getBoolPref("browser.startup.record", false)) {
+        this._resolve();
+        this._resolve = null;
+        return;
+      }
+
       // We use idleDispatchToMainThread here to record the set of
       // loaded scripts after we are fully done with startup and ready
       // to react to user events.

js/xpconnect/idl/xpcIJSModuleLoader.idl

@@ -8,11 +8,17 @@
 [scriptable, builtinclass, uuid(4f94b21f-2920-4bd9-8251-5fb60fb054b2)]
 interface xpcIJSModuleLoader : nsISupports
 {
-  // These 2 functions are for startup testing purposes. They are not expected
+  // These functions are for startup testing purposes. They are not expected
   // to be used for production code.
   void loadedModules([optional] out unsigned long length,
                      [retval, array, size_is(length)] out string aModules);
 
   void loadedComponents([optional] out unsigned long length,
                         [retval, array, size_is(length)] out string aComponents);
+
+  // These 2 functions will only return useful values if the
+  // "browser.startup.record" preference was true at the time the JS file
+  // was loaded.
+  ACString getModuleImportStack(in AUTF8String aLocation);
+  ACString getComponentLoadStack(in AUTF8String aLocation);
 };

js/xpconnect/loader/mozJSComponentLoader.cpp

@@ -433,6 +433,12 @@ mozJSComponentLoader::LoadModule(FileLocation& aFile)
         return nullptr;
     }
 
+#if defined(NIGHTLY_BUILD) || defined(DEBUG)
+    if (Preferences::GetBool("browser.startup.record", false)) {
+        entry->importStack = xpc_PrintJSStack(cx, false, false, false).get();
+    }
+#endif
+
     // Cache this module for later
     mModules.Put(spec, entry);
 
@@ -1000,6 +1006,52 @@ NS_IMETHODIMP mozJSComponentLoader::LoadedComponents(uint32_t* length,
     return NS_OK;
 }
 
+NS_IMETHODIMP
+mozJSComponentLoader::GetModuleImportStack(const nsACString& aLocation,
+                                           nsACString& retval)
+{
+#if defined(NIGHTLY_BUILD) || defined(DEBUG)
+    MOZ_ASSERT(nsContentUtils::IsCallerChrome());
+    MOZ_ASSERT(mInitialized);
+
+    ComponentLoaderInfo info(aLocation);
+    nsresult rv = info.EnsureKey();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    ModuleEntry* mod;
+    if (!mImports.Get(info.Key(), &mod))
+        return NS_ERROR_FAILURE;
+
+    retval = mod->importStack;
+    return NS_OK;
+#else
+    return NS_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
+NS_IMETHODIMP
+mozJSComponentLoader::GetComponentLoadStack(const nsACString& aLocation,
+                                            nsACString& retval)
+{
+#if defined(NIGHTLY_BUILD) || defined(DEBUG)
+    MOZ_ASSERT(nsContentUtils::IsCallerChrome());
+    MOZ_ASSERT(mInitialized);
+
+    ComponentLoaderInfo info(aLocation);
+    nsresult rv = info.EnsureURI();
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    ModuleEntry* mod;
+    if (!mModules.Get(info.Key(), &mod))
+        return NS_ERROR_FAILURE;
+
+    retval = mod->importStack;
+    return NS_OK;
+#else
+    return NS_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
 static JSObject*
 ResolveModuleObjectPropertyById(JSContext* aCx, HandleObject aModObj, HandleId id)
 {
@@ -1100,6 +1152,13 @@ mozJSComponentLoader::ImportInto(const nsACString& aLocation,
             return NS_ERROR_FILE_NOT_FOUND;
         }
 
+#if defined(NIGHTLY_BUILD) || defined(DEBUG)
+        if (Preferences::GetBool("browser.startup.record", false)) {
+            newEntry->importStack =
+                xpc_PrintJSStack(callercx, false, false, false).get();
+        }
+#endif
+
         mod = newEntry;
     }
 

js/xpconnect/loader/mozJSComponentLoader.h

@@ -163,6 +163,9 @@ class mozJSComponentLoader final : public mozilla::ModuleLoader,
             obj = nullptr;
             thisObjectKey = nullptr;
             location = nullptr;
+#if defined(NIGHTLY_BUILD) || defined(DEBUG)
+            importStack.Truncate();
+#endif
         }
 
         size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
@@ -175,6 +178,9 @@ class mozJSComponentLoader final : public mozilla::ModuleLoader,
         JS::PersistentRootedScript thisObjectKey;
         char* location;
         nsCString resolvedURL;
+#if defined(NIGHTLY_BUILD) || defined(DEBUG)
+        nsCString importStack;
+#endif
     };
 
     static size_t DataEntrySizeOfExcludingThis(const nsACString& aKey, ModuleEntry* const& aData,