Fix native Closure Compiler to work.

emsdk.py

@@ -1402,6 +1402,8 @@ def emscripten_npm_install(tool, directory):
   env = os.environ.copy()
   env["PATH"] = node_path + os.pathsep + env["PATH"]
   print('Running post-install step: npm ci ...')
+  # Do a --no-optional install to avoid bloating disk size:
+  # https://github.com/emscripten-core/emscripten/issues/12406
   try:
     subprocess.check_output(
         [npm, 'ci', '--production', '--no-optional'],
@@ -1411,6 +1413,66 @@ def emscripten_npm_install(tool, directory):
     errlog('Error running %s:\n%s' % (e.cmd, e.output))
     return False
 
+  # Manually install the appropriate native Closure Compiler package
+  # This is currently needed because npm ci would install the packages
+  # for Closure for all platforms, adding 180MB to the download size
+  # There are two problems here:
+  #   1. npm ci does not consider the platform of optional dependencies
+  #      https://github.com/npm/cli/issues/558
+  #   2. A bug with the native compiler has bloated the packages from
+  #      30MB to almost 300MB
+  #      https://github.com/google/closure-compiler-npm/issues/186
+  # If either of these bugs are fixed then we can remove this exception
+  # See also https://github.com/google/closure-compiler/issues/3925
+  closure_compiler_native = ''
+  if LINUX and ARCH in ('x86', 'x86_64'):
+    closure_compiler_native = 'google-closure-compiler-linux'
+  if MACOS and ARCH in ('x86', 'x86_64'):
+    closure_compiler_native = 'google-closure-compiler-osx'
+  if WINDOWS and ARCH == 'x86_64':
+    closure_compiler_native = 'google-closure-compiler-windows'
+
+  if closure_compiler_native:
+    # Check which version of native Closure Compiler we want to install via npm.
+    # (npm install command has this requirement that we must explicitly tell the pinned version)
+    try:
+      closure_version = json.load(open(os.path.join(directory, 'package.json')))['dependencies']['google-closure-compiler']
+    except KeyError as e:
+      # The target version of Emscripten does not (did not) have a package.json that would contain google-closure-compiler. (fastcomp)
+      # Skip manual native google-closure-compiler installation there.
+      print(str(e))
+      print('Emscripten version does not have a npm package.json with google-closure-compiler dependency, skipping native google-closure-compiler install step')
+      return True
+
+    closure_compiler_native += '@' + closure_version
+    print('Running post-install step: npm install', closure_compiler_native)
+    try:
+      subprocess.check_output(
+        [npm, 'install', '--production', '--no-optional', closure_compiler_native],
+        cwd=directory, stderr=subprocess.STDOUT, env=env,
+        universal_newlines=True)
+
+      # Installation of native Closure compiler was successful, so remove import of Java Closure Compiler module to avoid
+      # a Java dependency.
+      compiler_filename = os.path.join(directory, 'node_modules', 'google-closure-compiler', 'lib', 'node', 'closure-compiler.js')
+      if os.path.isfile(compiler_filename):
+        old_js = open(compiler_filename, 'r').read()
+        new_js = old_js.replace("require('google-closure-compiler-java')", "''/*require('google-closure-compiler-java') XXX Removed by Emsdk*/")
+        if old_js == new_js:
+          raise Exception('Failed to patch google-closure-compiler-java dependency away!')
+        open(compiler_filename, 'w').write(new_js)
+
+        # Now that we succeeded to install the native version and patch away the Java dependency, delete the Java version
+        # since that takes up ~12.5MB of installation space that is no longer needed.
+        # This process is currently a little bit hacky, see https://github.com/google/closure-compiler/issues/3926
+        remove_tree(os.path.join(directory, 'node_modules', 'google-closure-compiler-java'))
+        print('Removed google-closure-compiler-java dependency.')
+      else:
+        errlog('Failed to patch away google-closure-compiler Java dependency. ' + compiler_filename + ' does not exist.')
+    except subprocess.CalledProcessError as e:
+      errlog('Error running %s:\n%s' % (e.cmd, e.output))
+      return False
+
   print('Done running: npm ci')
   return True