GN files for running Closure Compiler

third_party/closure_compiler/compile_js2.gni

+# Copyright 2016 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.
+
+import("closure_args.gni")
+
+template("compile_js") {
+  # This template optionally takes these arguments:
+  # - sources: a list of all of the source files to be compiled. Required.
+  # - out_file: a file where the compiled output is written to. The default
+  #             is ${target_gen_dir}/closure/${target_name}.js".
+  # - script_args: additional arguments to pass to compile.py.
+  # - closure_args: additional arguments to pass to the Closure compiler.
+  # - disabled_closure_args: additional arguments dealing with the
+  #                          strictness of compilation; Non-strict
+  #                          defaults are provided that can be overriden.
+  # - externs: externs required to compile the sources
+  # - interfaces: interfaces required to compile the sources
+  forward_variables_from(invoker,
+                         [
+                           "source_files",
+                           "deps",
+                           "out_file",
+                           "script_args",
+                           "closure_args",
+                           "runner_args",
+                           "disabled_closure_args",
+                           "externs",
+                           "interfaces",
+                         ])
+
+  CLOSURE_DIR = "//third_party/closure_compiler"
+
+  action(target_name) {
+    assert(defined(source_files))
+
+    # assign the sources to data to create run-time list of sources from the
+    # dependency tree

[Dan Beam, 2016/08/19 01:55:19]

can actions have dependencies?  if so, we just kind of need to do a dependency
order set union here i think

[aberent, 2016/09/06 13:22:29]

Yes, actions can have dependencies. The problem is that, as I understand it, GN
is single pass. As such it does not know the full dependency tree of any target
until the GN run is finished, so one cannot read that dependency tree within GN.
 The best it can do is create a file containing a data dependency list that can
be read at ninja time (see the discussion in the email thread).

Dirk may be able to correct me, or comment further.

I have just realised, however that this comment is totally the wrong place! It
should be a comment on line 80, 'data = sources'.

+    if (!defined(runner_args)) {
+      runner_args = [ "enable-chrome-pass" ]
+    }
+    if (!defined(script_args)) {
+      script_args = []
+    }
+    if (!defined(closure_args)) {
+      closure_args = common_closure_args + checking_closure_args
+    }
+    if (!defined(disabled_closure_args)) {
+      disabled_closure_args = default_disabled_closure_args
+    }
+    if (!defined(out_file)) {
+      out_file = "${target_gen_dir}/closure/${target_name}.js"
+    }
+    inputs = [
+      "${CLOSURE_DIR}/compile.py",
+      "${CLOSURE_DIR}/processor.py",
+      "${CLOSURE_DIR}/build/inputs.py",
+      "${CLOSURE_DIR}/build/outputs.py",
+      "${CLOSURE_DIR}/compiler/compiler.jar",
+      "${CLOSURE_DIR}/runner/runner.jar",
+    ]
+
+    sources = source_files
+
+    if (defined(externs)) {
+      EXTERNS_DIR = "${CLOSURE_DIR}/externs"
+      foreach(extern, externs) {
+        sources += [ "$EXTERNS_DIR/$extern" ]
+      }
+    }
+    if (defined(interfaces)) {
+      INTERFACES_DIR = "${CLOSURE_DIR}/interfaces"
+      foreach(interface, interfaces) {
+        sources += [ "$INTERFACES_DIR/$interface" ]
+      }
+    }
+    outputs = [
+      out_file,
+    ]
+    data = sources
+    source_list_file =
+        "${target_gen_dir}/closure/${target_name}_source_list_file"
+    write_runtime_deps = source_list_file
+
+    script = "${CLOSURE_DIR}/compile2.py"
+    args = script_args + rebase_path(sources)
+    args += [
+      "--out_file",
+      rebase_path(out_file),
+    ]
+    args += [
+      "--source_list_file",
+      rebase_path(source_list_file),
+    ]
+    args += [ "--runner_args" ] + runner_args
+    args += [ "--closure_args" ] + closure_args + disabled_closure_args
+  }
+}