tools/gn/template.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "tools/gn/template.h"
   6
   7 #include "tools/gn/err.h"
   8 #include "tools/gn/functions.h"
   9 #include "tools/gn/parse_tree.h"
  10 #include "tools/gn/scope.h"
  11 #include "tools/gn/scope_per_file_provider.h"
  12 #include "tools/gn/value.h"
  13
  14 Template::Template(const Scope* scope, const FunctionCallNode* def)
  15     : closure_(scope->MakeClosure()),
  16       definition_(def) {
  17 }
  18
  19 Template::Template(scoped_ptr<Scope> scope, const FunctionCallNode* def)
  20     : closure_(scope.Pass()),
  21       definition_(def) {
  22 }
  23
  24 Template::~Template() {
  25 }
  26
  27 Value Template::Invoke(Scope* scope,
  28                        const FunctionCallNode* invocation,
  29                        const std::vector<Value>& args,
  30                        BlockNode* block,
  31                        Err* err) const {
  32   // Don't allow templates to be executed from imported files. Imports are for
  33   // simple values only.
  34   if (!EnsureNotProcessingImport(invocation, scope, err))
  35     return Value();
  36
  37   // First run the invocation's block. Need to allocate the scope on the heap
  38   // so we can pass ownership to the template.
  39   scoped_ptr<Scope> invocation_scope(new Scope(scope));
  40   if (!FillTargetBlockScope(scope, invocation,
  41                             invocation->function().value().as_string(),
  42                             block, args, invocation_scope.get(), err))
  43     return Value();
  44   block->Execute(invocation_scope.get(), err);
  45   if (err->has_error())
  46     return Value();
  47
  48   // Set up the scope to run the template and set the current directory for the
  49   // template (which ScopePerFileProvider uses to base the target-related
  50   // variables target_gen_dir and target_out_dir on) to be that of the invoker.
  51   // This way, files don't have to be rebased and target_*_dir works the way
  52   // people expect (otherwise its to easy to be putting generated files in the
  53   // gen dir corresponding to an imported file).
  54   Scope template_scope(closure_.get());
  55   template_scope.set_source_dir(scope->GetSourceDir());
  56
  57   ScopePerFileProvider per_file_provider(&template_scope, true);
  58
  59   // Targets defined in the template go in the collector for the invoking file.
  60   template_scope.set_item_collector(scope->GetItemCollector());
  61
  62   // We jump through some hoops to avoid copying the invocation scope when
  63   // setting it in the template scope (since the invocation scope may have
  64   // large lists of source files in it and could be expensive to copy).
  65   //
  66   // Scope.SetValue will copy the value which will in turn copy the scope, but
  67   // if we instead create a value and then set the scope on it, the copy can
  68   // be avoided.
  69   const char kInvoker[] = "invoker";
  70   template_scope.SetValue(kInvoker, Value(nullptr, scoped_ptr<Scope>()),
  71                           invocation);
  72   Value* invoker_value = template_scope.GetMutableValue(kInvoker, false);
  73   invoker_value->SetScopeValue(invocation_scope.Pass());
  74   template_scope.set_source_dir(scope->GetSourceDir());
  75
  76   const base::StringPiece target_name("target_name");
  77   template_scope.SetValue(target_name,
  78                           Value(invocation, args[0].string_value()),
  79                           invocation);
  80
  81   // Actually run the template code.
  82   Value result =
  83       definition_->block()->Execute(&template_scope, err);
  84   if (err->has_error()) {
  85     // If there was an error, append the caller location so the error message
  86     // displays a stack trace of how it got here.
  87     err->AppendSubErr(Err(invocation, "whence it was called."));
  88     return Value();
  89   }
  90
  91   // Check for unused variables in the invocation scope. This will find typos
  92   // of things the caller meant to pass to the template but the template didn't
  93   // read out.
  94   //
  95   // This is a bit tricky because it's theoretically possible for the template
  96   // to overwrite the value of "invoker" and free the Scope owned by the
  97   // value. So we need to look it up again and don't do anything if it doesn't
  98   // exist.
  99   invoker_value = template_scope.GetMutableValue(kInvoker, false);
 100   if (invoker_value && invoker_value->type() == Value::SCOPE) {
 101     if (!invoker_value->scope_value()->CheckForUnusedVars(err))
 102       return Value();
 103   }
 104
 105   // Check for unused variables in the template itself.
 106   if (!template_scope.CheckForUnusedVars(err))
 107     return Value();
 108
 109   return result;
 110 }
 111
 112 LocationRange Template::GetDefinitionRange() const {
 113   return definition_->GetRange();
 114 }