Add optional public header checking to GN build

tools/gn/header_checker.cc

Index: tools/gn/header_checker.cc
diff --git a/tools/gn/header_checker.cc b/tools/gn/header_checker.cc
new file mode 100644
index 0000000000000000000000000000000000000000..54dfb50c8a7e3fe6bbdc889cb6464faa5af5bb77
--- /dev/null
+++ b/tools/gn/header_checker.cc
@@ -0,0 +1,242 @@
+// Copyright 2014 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.
+
+#include "tools/gn/header_checker.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/file_util.h"
+#include "base/message_loop/message_loop.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "tools/gn/build_settings.h"
+#include "tools/gn/builder.h"
+#include "tools/gn/c_include_iterator.h"
+#include "tools/gn/err.h"
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/scheduler.h"
+#include "tools/gn/target.h"
+#include "tools/gn/trace.h"
+
+HeaderChecker::HeaderChecker(const BuildSettings* build_settings,
+                             const std::vector<const Target*>& targets)
+    : main_loop_(base::MessageLoop::current()),
+      build_settings_(build_settings) {
+  for (size_t i = 0; i < targets.size(); i++)
+    AddTargetToFileMap(targets[i]);
+}
+
+HeaderChecker::~HeaderChecker() {
+}
+
+bool HeaderChecker::Run(std::vector<Err>* errors) {
+  ScopedTrace trace(TraceItem::TRACE_CHECK_HEADERS, "Check headers");
+
+  if (file_map_.empty())
+    return true;
+
+  scoped_refptr<base::SequencedWorkerPool> pool(
+      new base::SequencedWorkerPool(16, "HeaderChecker"));
+  for (FileMap::const_iterator file_i = file_map_.begin();
+       file_i != file_map_.end(); ++file_i) {
+    const TargetVector& vect = file_i->second;
+
+    // Only check C-like source files (RC files also have includes).
+    SourceFileType type = GetSourceFileType(file_i->first);
+    if (type != SOURCE_CC && type != SOURCE_H && type != SOURCE_C &&
+        type != SOURCE_M && type != SOURCE_MM && type != SOURCE_RC)
+      continue;
+
+    for (size_t vect_i = 0; vect_i < vect.size(); ++vect_i) {
+      pool->PostWorkerTaskWithShutdownBehavior(
+          FROM_HERE,
+          base::Bind(&HeaderChecker::DoWork, this,
+                     vect[vect_i].target, file_i->first),
+          base::SequencedWorkerPool::BLOCK_SHUTDOWN);
+    }
+  }
+
+  // After this call we're single-threaded again.
+  pool->Shutdown();
+
+  if (errors_.empty())
+    return true;
+  *errors = errors_;
+  return false;
+}
+
+void HeaderChecker::DoWork(const Target* target, const SourceFile& file) {
+  Err err;
+  if (!CheckFile(target, file, &err)) {
+    base::AutoLock lock(lock_);
+    errors_.push_back(err);
+  }
+}
+
+void HeaderChecker::AddTargetToFileMap(const Target* target) {
+  // Files in the sources have this public bit by default.
+  bool default_public = target->all_headers_public();
+
+  // First collect the normal files, they get the default visibility.
+  std::map<SourceFile, bool> files_to_public;
+  const Target::FileList& sources = target->sources();
+  for (size_t i = 0; i < sources.size(); i++)
+    files_to_public[sources[i]] = default_public;
+
+  // Add in the public files, forcing them to public. This may overwrite some
+  // entries, and it may add new ones.
+  const Target::FileList& public_list = target->public_headers();
+  if (default_public)
+    DCHECK(public_list.empty());  // List only used when default is not public.
+  for (size_t i = 0; i < public_list.size(); i++)
+    files_to_public[public_list[i]] = true;
+
+  // Add the merged list to the master list of all files.
+  for (std::map<SourceFile, bool>::const_iterator i = files_to_public.begin();
+       i != files_to_public.end(); ++i)
+    file_map_[i->first].push_back(TargetInfo(target, i->second));
+}
+
+bool HeaderChecker::IsFileInOuputDir(const SourceFile& file) const {
+  const std::string& build_dir = build_settings_->build_dir().value();
+  return file.value().compare(0, build_dir.size(), build_dir) == 0;
+}
+
+// This current assumes all include paths are relative to the source root
+// which is generally the case for Chromium.
+//
+// A future enhancement would be to search the include path for the target
+// containing the source file containing this include and find the file to
+// handle the cases where people do weird things with the paths.
+SourceFile HeaderChecker::SourceFileForInclude(
+    const base::StringPiece& input) const {
+  std::string str("//");
+  input.AppendToString(&str);
+  return SourceFile(str);
+}
+
+bool HeaderChecker::CheckFile(const Target* from_target,
+                              const SourceFile& file,
+                              Err* err) const {
+  ScopedTrace trace(TraceItem::TRACE_CHECK_HEADER, file.value());
+
+  // Sometimes you have generated source files included as sources in another
+  // target. These won't exist at checking time. Since we require all generated
+  // files to be somewhere in the output tree, we can just check the name to
+  // see if they should be skipped.
+  if (IsFileInOuputDir(file))
+    return true;
+
+  base::FilePath path = build_settings_->GetFullPath(file);
+  std::string contents;
+  if (!base::ReadFileToString(path, &contents)) {
+    *err = Err(from_target->defined_from(), "Source file not found.",
+        "This target includes as a source:\n  " + file.value() +
+        "\nwhich was not found.");
+    return false;
+  }
+
+  CIncludeIterator iter(contents);
+  base::StringPiece current_include;
+  while (iter.GetNextIncludeString(&current_include)) {
+    SourceFile include = SourceFileForInclude(current_include);
+    if (!CheckInclude(from_target, file, include, err))
+      return false;
+  }
+
+  return true;
+}
+
+// If the file exists, it must be in a dependency of the given target, and it
+// must be public in that dependency.
+bool HeaderChecker::CheckInclude(const Target* from_target,
+                                 const SourceFile& source_file,
+                                 const SourceFile& include_file,
+                                 Err* err) const {
+  // Assume if the file isn't declared in our sources that we don't need to
+  // check it. It would be nice if we could give an error if this happens, but
+  // our include finder is too primitive and returns all includes, even if
+  // they're in a #if not executed in the current build. In that case, it's
+  // not unusual for the buildfiles to not specify that header at all.
+  FileMap::const_iterator found = file_map_.find(include_file);
+  if (found == file_map_.end())
+    return true;
+
+  const TargetVector& targets = found->second;
+
+  // For all targets containing this file, we require that at least one be
+  // a dependency of the current target, and all targets that are dependencies
+  // must have the file listed in the public section.
+  bool found_dependency = false;
+  for (size_t i = 0; i < targets.size(); i++) {
+    // We always allow source files in a target to include headers also in that
+    // target.
+    if (targets[i].target == from_target)
+      return true;
+
+    if (IsDependencyOf(targets[i].target, from_target)) {
+      // The include is in a target that's a proper dependency. Now verify
+      // that the include is a public file.
+      if (!targets[i].is_public) {
+        // Depending on a private header.
+        std::string msg = "The file " + source_file.value() +
+            "\nincludes " + include_file.value() +
+            "\nwhich is private to the target " +
+            targets[i].target->label().GetUserVisibleName(false);
+
+        // TODO(brettw) blame the including file.
+        *err = Err(NULL, "Including a private header.", msg);
+        return false;
+      }
+      found_dependency = true;
+    }
+  }
+
+  if (!found_dependency) {
+    std::string msg =
+        source_file.value() + " includes the header\n" +
+        include_file.value() + " which is not in any dependency of\n" +
+        from_target->label().GetUserVisibleName(false);
+    msg += "\n\nThe include file is in the target(s):\n";
+    for (size_t i = 0; i < targets.size(); i++)
+      msg += "  " + targets[i].target->label().GetUserVisibleName(false) + "\n";
+
+    msg += "\nMake sure one of these is a direct or indirect dependency\n"
+        "of " + from_target->label().GetUserVisibleName(false);
+
+    // TODO(brettw) blame the including file.
+    // Probably this means making and leaking an input file for it, and also
+    // tracking the locations for each include.
+    *err = Err(NULL, "Include not allowed.", msg);
+    return false;
+  }
+
+  return true;
+}
+
+bool HeaderChecker::IsDependencyOf(const Target* search_for,
+                                   const Target* search_from) const {
+  std::set<const Target*> checked;
+  return IsDependencyOf(search_for, search_from, &checked);
+}
+
+bool HeaderChecker::IsDependencyOf(const Target* search_for,
+                                   const Target* search_from,
+                                   std::set<const Target*>* checked) const {
+  if (checked->find(search_for) != checked->end())
+    return false;  // Already checked this subtree.
+
+  const LabelTargetVector& deps = search_from->deps();
+  for (size_t i = 0; i < deps.size(); i++) {
+    if (deps[i].ptr == search_for)
+      return true;  // Found it.
+
+    // Recursive search.
+    checked->insert(deps[i].ptr);
+    if (IsDependencyOf(search_for, deps[i].ptr, checked))
+      return true;
+  }
+
+  return false;
+}