WebstorePrivate extension API cleanup, part 1

extensions/browser/extension_function.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef EXTENSIONS_BROWSER_EXTENSION_FUNCTION_H_
 #define EXTENSIONS_BROWSER_EXTENSION_FUNCTION_H_
 
 #include <list>
 #include <string>
 
@@ skipping 290 matching lines @@
   // by the corresponding |s*|:
   // Error("Error in *: *", "foo", "bar") <--> Error("Error in foo: bar").
   ResponseValue Error(const std::string& format, const std::string& s1);
   ResponseValue Error(const std::string& format,
                       const std::string& s1,
                       const std::string& s2);
   ResponseValue Error(const std::string& format,
                       const std::string& s1,
                       const std::string& s2,
                       const std::string& s3);
+  // Error with a list of arguments |results| to pass to caller. TAKES OWNERSHIP
+  // - a scoped_ptr<> for convenience, since callers usually get this from the
+  // result of a Create(...) call on the generated Results struct, for example,
+  // alarms::Get::Results::Create(alarm).

[not at google - send to devlin, 2015/02/05 17:16:17]

It's funny actually - this ResponseAction/ResponseValue was a big refactor I did
a few months ago to avoid this exact scenario - APIs specifying both an error
and a result. It's supposed to be illegal, but some APIs (notably
webstorePrivate) still do it.

One big motivating factor is that if we convert to Promise APIs we won't have a
chance to pass errors and values in, since they're 2 separate callbacks. In that
situation we'd extend Error() to also take a Value instead of these format
strings.

However, given webstorePrivate does actually rely on this behavior, I suppose we
need to account for it.

I'd write it a little differently, in the spirit of better composition with
NoArguments/OneArgument/etc family -

// Using this ResponseValue indicates something is wrong with the API.
// It shouldn't be possible to have both an error *and* some arguments.
// Some legacy APIs do rely on it though, like webstorePrivate.
ResponseValue ErrorWithArguments(ResponseValue error, ResponseValue args)

[Marc Treib, 2015/02/06 10:26:15]

Done.

+  ResponseValue ArgumentListWithError(scoped_ptr<base::ListValue> results,
+                                      const std::string& error);
   // Bad message. A ResponseValue equivalent to EXTENSION_FUNCTION_VALIDATE(),
   // so this will actually kill the renderer and not respond at all.
   ResponseValue BadMessage();
 
   // ResponseActions.
   //
   // Respond to the extension immediately with |result|.
   ResponseAction RespondNow(ResponseValue result);
   // Don't respond now, but promise to call Respond(...) later.
   ResponseAction RespondLater();
@@ skipping 304 matching lines @@
   virtual bool RunSync() = 0;
 
   // ValidationFailure override to match RunSync().
   static bool ValidationFailure(SyncIOThreadExtensionFunction* function);
 
  private:
   ResponseAction Run() override;
 };
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_FUNCTION_H_