Bug 1366511: Part 2 - Allow autoconverting Err(nsresult) to nsresult. r=ehsan,nbp

This allows MOZ_TRY and MOZ_TRY_VAR to be transparently used in XPCOM methods
when compatible Result types are used.

Also removes a compatibility macro in SimpleChannel.cpp, and an identical
specialization in AddonManagerStartup, which are no longer necessary after
this change.

MozReview-Commit-ID: 94iNrPDJEnN

--HG--
extra : rebase_source : 24ad4a54cbd170eb04ded21794530e56b1dfbd82

js/xpconnect/loader/ScriptPreloader-inl.h

@@ -11,7 +11,7 @@
 #include "mozilla/CheckedInt.h"
 #include "mozilla/EnumSet.h"
 #include "mozilla/Range.h"
-#include "mozilla/Result.h"
+#include "mozilla/ResultExtensions.h"
 #include "mozilla/Unused.h"
 #include "mozilla/dom/ScriptSettings.h"
 #include "nsString.h"
@@ -21,21 +21,6 @@
 
 namespace mozilla {
 
-// A specialization of GenericErrorResult which auto-converts to a nsresult.
-// This should be removed when bug 1366511 is fixed.
-template <>
-class MOZ_MUST_USE_TYPE GenericErrorResult<nsresult>
-{
-  nsresult mErrorValue;
-
-  template<typename V, typename E2> friend class Result;
-
-public:
-  explicit GenericErrorResult(nsresult aErrorValue) : mErrorValue(aErrorValue) {}
-
-  operator nsresult() { return mErrorValue; }
-};
-
 namespace loader {
 
 using mozilla::dom::AutoJSAPI;

js/xpconnect/loader/ScriptPreloader.cpp

@@ -4,8 +4,8 @@
  * 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/. */
 
-#include "mozilla/ScriptPreloader.h"
 #include "ScriptPreloader-inl.h"
+#include "mozilla/ScriptPreloader.h"
 #include "mozilla/loader/ScriptCacheActors.h"
 
 #include "mozilla/ArrayUtils.h"

mfbt/ResultExtensions.h

@@ -0,0 +1,37 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * 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/. */
+
+/* Extensions to the Result type to enable simpler handling of XPCOM/NSPR results. */
+
+#ifndef mozilla_ResultExtensions_h
+#define mozilla_ResultExtensions_h
+
+#include "mozilla/Assertions.h"
+#include "nscore.h"
+
+namespace mozilla {
+
+// Allow nsresult errors to automatically convert to nsresult values, so MOZ_TRY
+// can be used in XPCOM methods with Result<T, nserror> results.
+template <>
+class MOZ_MUST_USE_TYPE GenericErrorResult<nsresult>
+{
+  nsresult mErrorValue;
+
+  template<typename V, typename E2> friend class Result;
+
+public:
+  explicit GenericErrorResult(nsresult aErrorValue) : mErrorValue(aErrorValue)
+  {
+    MOZ_ASSERT(NS_FAILED(aErrorValue));
+  }
+
+  operator nsresult() { return mErrorValue; }
+};
+
+} // namespace mozilla
+
+#endif // mozilla_ResultExtensions_h

mfbt/moz.build

@@ -76,6 +76,7 @@ EXPORTS.mozilla = [
     'RefCountType.h',
     'RefPtr.h',
     'Result.h',
+    'ResultExtensions.h',
     'ReverseIterator.h',
     'RollingMean.h',
     'Saturate.h',

netwerk/base/SimpleChannel.cpp

@@ -21,18 +21,6 @@
 namespace mozilla {
 namespace net {
 
-// Like MOZ_TRY, but returns the unwrapped error value rather than a
-// GenericErrorResult on failure.
-#define TRY_VAR(target, expr) \
-  do { \
-    auto result = (expr); \
-    if (result.isErr()) { \
-      return result.unwrapErr(); \
-    } \
-    (target) = result.unwrap(); \
-  } while (0)
-
-
 class SimpleChannel : public nsBaseChannel
 {
 public:
@@ -63,7 +51,7 @@ SimpleChannel::OpenContentStream(bool async, nsIInputStream **streamOut, nsIChan
   NS_ENSURE_TRUE(mCallbacks, NS_ERROR_UNEXPECTED);
 
   nsCOMPtr<nsIInputStream> stream;
-  TRY_VAR(stream, mCallbacks->OpenContentStream(async, this));
+  MOZ_TRY_VAR(stream, mCallbacks->OpenContentStream(async, this));
   MOZ_ASSERT(stream);
 
   mCallbacks = nullptr;
@@ -79,7 +67,7 @@ SimpleChannel::BeginAsyncRead(nsIStreamListener* listener, nsIRequest** request)
   NS_ENSURE_TRUE(mCallbacks, NS_ERROR_UNEXPECTED);
 
   nsCOMPtr<nsIRequest> req;
-  TRY_VAR(req, mCallbacks->StartAsyncRead(listener, this));
+  MOZ_TRY_VAR(req, mCallbacks->StartAsyncRead(listener, this));
 
   mCallbacks = nullptr;
 
@@ -87,8 +75,6 @@ SimpleChannel::BeginAsyncRead(nsIStreamListener* listener, nsIRequest** request)
   return NS_OK;
 }
 
-#undef TRY_VAR
-
 class SimpleChannelChild final : public SimpleChannel
                                , public nsIChildChannel
                                , public PSimpleChannelChild

netwerk/base/SimpleChannel.h

@@ -6,7 +6,7 @@
 #ifndef SimpleChannel_h
 #define SimpleChannel_h
 
-#include "mozilla/Result.h"
+#include "mozilla/ResultExtensions.h"
 #include "mozilla/UniquePtr.h"
 #include "nsCOMPtr.h"
 

netwerk/protocol/res/ExtensionProtocolHandler.cpp

@@ -52,19 +52,6 @@ using OptionalIPCStream = mozilla::ipc::OptionalIPCStream;
 
 namespace mozilla {
 
-template <>
-class MOZ_MUST_USE_TYPE GenericErrorResult<nsresult>
-{
-  nsresult mErrorValue;
-
-  template<typename V, typename E2> friend class Result;
-
-public:
-  explicit GenericErrorResult(nsresult aErrorValue) : mErrorValue(aErrorValue) {}
-
-  operator nsresult() { return mErrorValue; }
-};
-
 namespace net {
 
 using extensions::URLInfo;

netwerk/protocol/res/ExtensionProtocolHandler.h

@@ -8,6 +8,7 @@
 
 #include "mozilla/net/NeckoParent.h"
 #include "mozilla/LazyIdleThread.h"
+#include "mozilla/Result.h"
 #include "SubstitutingProtocolHandler.h"
 
 namespace mozilla {

toolkit/components/extensions/WebExtensionPolicy.cpp

@@ -8,6 +8,7 @@
 #include "mozilla/extensions/WebExtensionPolicy.h"
 
 #include "mozilla/AddonManagerWebAPI.h"
+#include "mozilla/ResultExtensions.h"
 #include "nsEscape.h"
 #include "nsISubstitutingProtocolHandler.h"
 #include "nsNetUtil.h"

toolkit/mozapps/extensions/AddonManagerStartup.cpp

@@ -16,6 +16,7 @@
 #include "mozilla/Compression.h"
 #include "mozilla/LinkedList.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/ResultExtensions.h"
 #include "mozilla/ScopeExit.h"
 #include "mozilla/Services.h"
 #include "mozilla/Unused.h"
@@ -42,19 +43,6 @@
 
 namespace mozilla {
 
-template <>
-class MOZ_MUST_USE_TYPE GenericErrorResult<nsresult>
-{
-  nsresult mErrorValue;
-
-  template<typename V, typename E2> friend class Result;
-
-public:
-  explicit GenericErrorResult(nsresult aErrorValue) : mErrorValue(aErrorValue) {}
-
-  operator nsresult() { return mErrorValue; }
-};
-
 static inline Result<Ok, nsresult>
 WrapNSResult(PRStatus aRv)
 {

xpcom/base/nscore.h

@@ -212,6 +212,9 @@ struct UnusedZero<nsresult>
   static const bool value = true;
 };
 } // namespace detail
+
+template <typename T> class MOZ_MUST_USE_TYPE GenericErrorResult;
+template <> class MOZ_MUST_USE_TYPE GenericErrorResult<nsresult>;
 } // namespace mozilla
 
 /*