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) {

[Dan Beam, 2016/09/07 18:18:05]

can we just automatically pref targets if we're doing to do that?  i.e.
"compile_js" + target_name here?

[aberent, 2016/09/08 10:29:18]

We could, and I wondered about this, but given that the dependencies have to be
on the full target name I thought that might confuse things more than clarifying
them.

The issue is that the BUILD.gn file would end up containing:


compile_js("a") {
 ...
}

compile_js("b") {
...
  deps = [":compile_js_a"]

}


Unless one knows then it might not be entirely obvious that the target
"compile_js_a" is created by the template (and, in particular, a text search
won't find it). In general the convention for template usage in GN seems to be
to pass the primary target name as the argument.

+    assert(defined(source_files))
+
+    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"

[Dan Beam, 2016/09/07 18:18:05]

why is this /closure/ here?  was this in the old system?

+    }
+    inputs = [
+      "${CLOSURE_DIR}/compile.py",
+      "${CLOSURE_DIR}/processor.py",
+      "${CLOSURE_DIR}/build/inputs.py",

[Dan Beam, 2016/09/07 18:18:05]

where are inputs.py or outputs.py invoked?  they used to be invoked as actions
to generate a list of dependent source files.  i don't see where that's
happening now...

[aberent, 2016/09/08 10:29:19]

Unless I have missed something inputs.py isn't actually used by
compile_js2.gypi, only by compile_js.gypi. We clearly can't use inputs.py in its
current form since it is reading the gyp files to find dependencies, but, in
principle, we should be able to use GN runtime_dependencies to get the file list
(although see my email of this morning).

output.py is doing some simple file name manipulation which can be done (I
think) by GN directly.

Although exec_script exists in GN it is generally a bad idea to run scripts at
GN time, since a slow script slows down GN for everybody (remember that one can
only have one BUILD.gn file per directory).

[Dan Beam, 2016/09/08 17:53:21]

yeah, I just want to remove from inputs = [] if we don't need them there

+      "${CLOSURE_DIR}/build/outputs.py",
+      "${CLOSURE_DIR}/compiler/compiler.jar",
+      "${CLOSURE_DIR}/runner/runner.jar",
+    ]
+
+    sources = source_files

[Dan Beam, 2016/09/07 18:18:05]

can we not use sources directly rather than "source_files" => "sources"?

[aberent, 2016/09/08 10:29:19]

I tried this originally, and it didn't seem to work. I am not exactly sure why,
but "sources" has a special meaning in actions, and assigning to it more than
once (or modifying it) seemed to confuse GN.

+
+    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,
+    ]
+
+    # assign the sources to data to create run-time list of sources from the
+    # dependency tree
+    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 += [
+      "--gn_source_list_file",
+      rebase_path(source_list_file),
+    ]
+    args += [ "--runner_args" ] + runner_args
+    args += [ "--closure_args" ] + closure_args + disabled_closure_args
+  }
+}