Bug 1768722 - Use std::ofstream in nsProfiler::DumpProfileToFileAsync, and reject promise in case of failure - r=florian,mixedpuppy

The geckoProfiler.dumpProfileToFile (extension API) needed to be updated, to create the target directory if necessary. Some xpcshell tests would fail otherwise.

Also improved nsIProfiler.idl docs of dumpProfileToFile{,Async}.

***
Use ofstream, fixed xpcshell tests.

Differential Revision: https://phabricator.services.mozilla.com/D148610

toolkit/components/extensions/parent/ext-geckoProfiler.js

@@ -8,6 +8,9 @@
 
 ChromeUtils.defineModuleGetter(this, "OS", "resource://gre/modules/osfile.jsm");
 
+// eslint-disable-next-line mozilla/reject-importGlobalProperties
+Cu.importGlobalProperties(["IOUtils", "PathUtils"]);
+
 const PREF_ASYNC_STACK = "javascript.options.asyncstack";
 
 const ASYNC_STACKS_ENABLED = Services.prefs.getBoolPref(
@@ -133,10 +136,14 @@ this.geckoProfiler = class extends ExtensionAPI {
             throw new ExtensionError("Path cannot contain a subdirectory.");
           }
 
-          let fragments = [OS.Constants.Path.profileDir, "profiler", fileName];
-          let filePath = OS.Path.join(...fragments);
+          let dirPath = PathUtils.join(
+            OS.Constants.Path.profileDir,
+            "profiler"
+          );
+          let filePath = PathUtils.join(dirPath, fileName);
 
           try {
+            await IOUtils.makeDirectory(dirPath);
             await Services.profiler.dumpProfileToFileAsync(filePath);
           } catch (e) {
             Cu.reportError(e);

tools/profiler/gecko/nsIProfiler.idl

@@ -93,12 +93,28 @@ interface nsIProfiler : nsISupports
   Promise getProfileDataAsGzippedArrayBuffer([optional] in double aSinceTime);
 
   /**
-   * Returns a promise that resolves once the file has been written.
+   * Asynchronously dump the profile collected so far to a file.
+   * Returns a promise that resolves once the file has been written, with data
+   * from all responsive Firefox processes. Note: This blocks the parent process
+   * while collecting its own data, then unblocks while child processes data is
+   * being collected.
+   * `aFilename` may be a full path, or a path relative to where Firefox was
+   * launched. The target directory must already exist.
    */
   [implicit_jscontext]
   Promise dumpProfileToFileAsync(in ACString aFilename,
                                  [optional] in double aSinceTime);
 
+  /**
+   * Synchronously dump the profile collected so far in this process to a file.
+   * This profile will only contain data from the parent process, and from child
+   * processes that have ended during the session; other currently-live
+   * processes are ignored.
+   * `aFilename` may be a full path, or a path relative to where Firefox was
+   * launched. The target directory must already exist.
+   */
+  void dumpProfileToFile(in string aFilename);
+
   boolean IsActive();
 
   /**
@@ -187,11 +203,6 @@ interface nsIProfiler : nsISupports
   [implicit_jscontext]
   Promise getSymbolTable(in ACString aDebugPath, in ACString aBreakpadID);
 
-  /**
-   * Dump the collected profile to a file.
-   */
-  void dumpProfileToFile(in string aFilename);
-
   %{C++
   virtual RefPtr<mozilla::MozPromise<FallibleTArray<uint8_t>, nsresult, true>> GetProfileDataAsGzippedArrayBufferAndroid(double aSinceTime) = 0;
   %}

tools/profiler/gecko/nsProfiler.cpp

@@ -6,6 +6,8 @@
 
 #include "nsProfiler.h"
 
+#include <fstream>
+#include <limits>
 #include <sstream>
 #include <string>
 #include <utility>
@@ -24,12 +26,10 @@
 #include "mozilla/dom/TypedArray.h"
 #include "mozilla/Preferences.h"
 #include "nsComponentManagerUtils.h"
-#include "nsIFileStreams.h"
 #include "nsIInterfaceRequestor.h"
 #include "nsIInterfaceRequestorUtils.h"
 #include "nsILoadContext.h"
 #include "nsIWebNavigation.h"
-#include "nsLocalFile.h"
 #include "nsMemory.h"
 #include "nsProfilerStartParams.h"
 #include "nsProxyRelease.h"
@@ -596,18 +596,21 @@ nsProfiler::DumpProfileToFileAsync(const nsACString& aFilename,
       ->Then(
           GetMainThreadSerialEventTarget(), __func__,
           [filename, promise](const nsCString& aResult) {
-            nsCOMPtr<nsIFile> file =
-                do_CreateInstance(NS_LOCAL_FILE_CONTRACTID);
-            nsresult rv = file->InitWithNativePath(filename);
-            if (NS_FAILED(rv)) {
-              MOZ_CRASH();
+            if (aResult.Length() >=
+                size_t(std::numeric_limits<std::streamsize>::max())) {
+              promise->MaybeReject(NS_ERROR_FILE_TOO_BIG);
+              return;
             }
-            nsCOMPtr<nsIFileOutputStream> of =
-                do_CreateInstance("@mozilla.org/network/file-output-stream;1");
-            of->Init(file, -1, -1, 0);
-            uint32_t sz;
-            of->Write(aResult.get(), aResult.Length(), &sz);
-            of->Close();
+
+            std::ofstream stream;
+            stream.open(filename.get());
+            if (!stream.is_open()) {
+              promise->MaybeReject(NS_ERROR_FILE_UNRECOGNIZED_PATH);
+              return;
+            }
+
+            stream.write(aResult.get(), std::streamsize(aResult.Length()));
+            stream.close();
 
             promise->MaybeResolveWithUndefined();
           },