Implement tracking of BUILD.gn files used to define target, toolchain or

tools/gn/scope.h

 // Copyright (c) 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 TOOLS_GN_SCOPE_H_
 #define TOOLS_GN_SCOPE_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 81 matching lines @@
     // so won't trigger an unused variable warning. You want this when doing an
     // import, for example, or files that don't need a variable from the .gni
     // file will throw an error.
     bool mark_dest_used;
 
     // When set, those variables are not merged.
     std::set<std::string> excluded_values;
   };
 
   // Creates an empty toplevel scope.
-  explicit Scope(const Settings* settings);
+  Scope(const Settings* settings,
+        const std::set<uint32_t>& source_files_hashes);

[brettw, 2017/06/27 00:50:40]

I believe a base::flat_set<uint32_t> will be more efficient in this use. set
will allocate for every insertion which will slow it down, and I suspect moving
ints for insertion will be much faster than a heap allocation. This will also be
much faster for making copies of the set (one allocation rather than N) which it
looks like the patch does a lot.

Maybe we want a typedef for this.

[alex-ac, 2017/06/27 13:46:31]

Done.

 
   // Creates a dependent scope.
   explicit Scope(Scope* parent);
   explicit Scope(const Scope* parent);
 
   ~Scope();
 
   const Settings* settings() const { return settings_; }
 
   // See the const_/mutable_containing_ var declarations below. Yes, it's a
@@ skipping 163 matching lines @@
   void SetProcessingImport();
   void ClearProcessingImport();
   bool IsProcessingImport() const;
 
   // The source directory associated with this scope. This will check embedded
   // scopes until it finds a nonempty source directory. This will default to
   // an empty dir if no containing scope has a source dir set.
   const SourceDir& GetSourceDir() const;
   void set_source_dir(const SourceDir& d) { source_dir_ = d; }
 
+  // The set of source files which affected this scope.
+  const std::set<uint32_t>& source_files_hashes() const {
+    return source_files_hashes_;
+  }
+  void AddSourceFile(const SourceFile& source_file);
+
   // The item collector is where Items (Targets, Configs, etc.) go that have
   // been defined. If a scope can generate items, this non-owning pointer will
   // point to the storage for such items. The creator of this scope will be
   // responsible for setting up the collector and then dealing with the
   // collected items once execution of the context is complete.
   //
   // The items in a scope are collected as we go and then dispatched at the end
   // of execution of a scope so that we can query the previously-generated
   // targets (like getting the outputs).
   //
@@ skipping 75 matching lines @@
 
   // Opaque pointers. See SetProperty() above.
   typedef std::map<const void*, void*> PropertyMap;
   PropertyMap properties_;
 
   typedef std::set<ProgrammaticProvider*> ProviderSet;
   ProviderSet programmatic_providers_;
 
   SourceDir source_dir_;
 
+  std::set<uint32_t> source_files_hashes_;
+
   DISALLOW_COPY_AND_ASSIGN(Scope);
 };
 
 #endif  // TOOLS_GN_SCOPE_H_