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// 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.
#include "tools/gn/err.h"
#include "tools/gn/functions.h"
#include "tools/gn/parse_tree.h"
#include "tools/gn/scope.h"
namespace functions {
namespace {
} // namespace
const char kForEach[] = "foreach";
const char kForEach_HelpShort[] =
"foreach: Iterate over a list.";
const char kForEach_Help[] =
"foreach: Iterate over a list.\n"
"\n"
" foreach(<loop_var>, <list>) {\n"
" <loop contents>\n"
" }\n"
"\n"
" Executes the loop contents block over each item in the list,\n"
" assigning the loop_var to each item in sequence.\n"
"\n"
" The block does not introduce a new scope, so that variable assignments\n"
" inside the loop will be visible once the loop terminates.\n"
"\n"
" The loop variable will temporarily shadow any existing variables with\n"
" the same name for the duration of the loop. After the loop terminates\n"
" the loop variable will no longer be in scope, and the previous value\n"
" (if any) will be restored.\n"
"\n"
"Example\n"
"\n"
" mylist = [ \"a\", \"b\", \"c\" ]\n"
" foreach(i, mylist) {\n"
" print(i)\n"
" }\n"
"\n"
" Prints:\n"
" a\n"
" b\n"
" c\n";
Value RunForEach(Scope* scope,
const FunctionCallNode* function,
const ListNode* args_list,
Err* err) {
const std::vector<const ParseNode*>& args_vector = args_list->contents();
if (args_vector.size() != 2) {
*err = Err(function, "Wrong number of arguments to foreach().",
"Expecting exactly two.");
return Value();
}
// Extract the loop variable.
const IdentifierNode* identifier = args_vector[0]->AsIdentifier();
if (!identifier) {
*err = Err(args_vector[0], "Expected an identifier for the loop var.");
return Value();
}
base::StringPiece loop_var(identifier->value().value());
// Extract the list, avoid a copy if it's an identifier (common case).
Value value_storage_for_exec; // Backing for list_value when we need to exec.
const Value* list_value = NULL;
const IdentifierNode* list_identifier = args_vector[1]->AsIdentifier();
if (list_identifier) {
list_value = scope->GetValue(list_identifier->value().value(), true);
if (!list_value) {
*err = Err(args_vector[1], "Undefined identifier.");
return Value();
}
} else {
// Not an identifier, evaluate the node to get the result.
Scope list_exec_scope(scope);
value_storage_for_exec = args_vector[1]->Execute(scope, err);
if (err->has_error())
return Value();
list_value = &value_storage_for_exec;
}
if (!list_value->VerifyTypeIs(Value::LIST, err))
return Value();
const std::vector<Value>& list = list_value->list_value();
// Block to execute.
const BlockNode* block = function->block();
if (!block) {
*err = Err(function, "Expected { after foreach.");
return Value();
}
// If the loop variable was previously defined in this scope, save it so we
// can put it back after the loop is done.
const Value* old_loop_value_ptr = scope->GetValue(loop_var);
Value old_loop_value;
if (old_loop_value_ptr)
old_loop_value = *old_loop_value_ptr;
for (const auto& cur : list) {
scope->SetValue(loop_var, cur, function);
block->ExecuteBlockInScope(scope, err);
if (err->has_error())
return Value();
}
// Put back loop var.
if (old_loop_value_ptr) {
// Put back old value. Use the copy we made, rather than use the pointer,
// which will probably point to the new value now in the scope.
scope->SetValue(loop_var, old_loop_value, old_loop_value.origin());
} else {
// Loop variable was undefined before loop, delete it.
scope->RemoveIdentifier(loop_var);
}
return Value();
}
} // namespace functions
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