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// 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 "gn/template.h"
#include <memory>
#include <utility>
#include "gn/err.h"
#include "gn/functions.h"
#include "gn/parse_tree.h"
#include "gn/scope.h"
#include "gn/scope_per_file_provider.h"
#include "gn/value.h"
#include "gn/variables.h"
Template::Template(const Scope* scope, const FunctionCallNode* def)
: closure_(scope->MakeClosure()), definition_(def) {}
Template::Template(std::unique_ptr<Scope> scope, const FunctionCallNode* def)
: closure_(std::move(scope)), definition_(def) {}
Template::~Template() = default;
Value Template::Invoke(Scope* scope,
const FunctionCallNode* invocation,
const std::string& template_name,
const std::vector<Value>& args,
BlockNode* block,
Err* err) const {
// Don't allow templates to be executed from imported files. Imports are for
// simple values only.
if (!EnsureNotProcessingImport(invocation, scope, err))
return Value();
// First run the invocation's block. Need to allocate the scope on the heap
// so we can pass ownership to the template.
std::unique_ptr<Scope> invocation_scope = std::make_unique<Scope>(scope);
if (!FillTargetBlockScope(scope, invocation, template_name, block, args,
invocation_scope.get(), err))
return Value();
// Don't allow the block of the template invocation to include other
// targets configs, or template invocations. This must only be applied
// to the invoker's block rather than the whole function because the
// template execution itself must be able to define targets, etc.
NonNestableBlock non_nestable(scope, invocation, "template invocation");
if (!non_nestable.Enter(err))
return Value();
block->Execute(invocation_scope.get(), err);
if (err->has_error())
return Value();
// Set up the scope to run the template and set the current directory for the
// template (which ScopePerFileProvider uses to base the target-related
// variables target_gen_dir and target_out_dir on) to be that of the invoker.
// This way, files don't have to be rebased and target_*_dir works the way
// people expect (otherwise its to easy to be putting generated files in the
// gen dir corresponding to an imported file).
Scope template_scope(closure_.get());
// Track the invocation of the template on the template's scope
template_name, args[0].string_value(), invocation->GetRange().begin());
// Propagate build dependency files from invoker scope (template scope already
// propagated via parent scope).
ScopePerFileProvider per_file_provider(&template_scope, true);
// Targets defined in the template go in the collector for the invoking file.
// We jump through some hoops to avoid copying the invocation scope when
// setting it in the template scope (since the invocation scope may have
// large lists of source files in it and could be expensive to copy).
// Scope.SetValue will copy the value which will in turn copy the scope, but
// if we instead create a value and then set the scope on it, the copy can
// be avoided.
Value(nullptr, std::unique_ptr<Scope>()), invocation);
Value* invoker_value = template_scope.GetMutableValue(
variables::kInvoker, Scope::SEARCH_NESTED, false);
const std::string_view target_name(variables::kTargetName);
target_name, Value(invocation, args[0].string_value()), invocation);
// Actually run the template code.
Value result = definition_->block()->Execute(&template_scope, err);
if (err->has_error()) {
// If there was an error, append the caller location so the error message
// displays a stack trace of how it got here.
err->AppendSubErr(Err(invocation, "whence it was called."));
return Value();
// Check for unused variables in the invocation scope. This will find typos
// of things the caller meant to pass to the template but the template didn't
// read out.
// This is a bit tricky because it's theoretically possible for the template
// to overwrite the value of "invoker" and free the Scope owned by the
// value. So we need to look it up again and don't do anything if it doesn't
// exist.
invoker_value = template_scope.GetMutableValue(variables::kInvoker,
Scope::SEARCH_NESTED, false);
if (invoker_value && invoker_value->type() == Value::SCOPE) {
if (!invoker_value->scope_value()->CheckForUnusedVars(err))
return Value();
// Check for unused variables in the template itself.
if (!template_scope.CheckForUnusedVars(err))
return Value();
return result;
LocationRange Template::GetDefinitionRange() const {
return definition_->GetRange();