add emcc option --generate-config (#6810)

fixes #6299

emcc.py

@@ -2319,6 +2319,14 @@ def parse_args(newargs):
         exit_with_error('Invalid value "' + newargs[i + 1] + '" to --output_eol!')
       newargs[i] = ''
       newargs[i + 1] = ''
+    elif newargs[i] == '--generate-config':
+      optarg = newargs[i + 1]
+      path = os.path.expanduser(optarg)
+      if os.path.exists(path):
+        exit_with_error('File ' + optarg + ' passed to --generate-config already exists!')
+      else:
+        shared.generate_config(optarg)
+      should_exit = True
 
   if should_exit:
     sys.exit(0)

tests/test_other.py

@@ -100,6 +100,16 @@ def test_emcc_python_version(self):
       assert expected_call not in output
       assert output == '', output
 
+  def test_emcc_generate_config(self):
+    for compiler in [EMCC, EMXX]:
+      config_path = './emscripten_config'
+      run_process([PYTHON, compiler, '--generate-config', config_path])
+      assert os.path.exists(config_path), 'A config file should have been created at %s' % config_path
+      config_contents = open(config_path).read()
+      self.assertContained('EMSCRIPTEN_ROOT', config_contents)
+      self.assertContained('LLVM_ROOT', config_contents)
+      os.remove(config_path)
+
   def test_emcc_1(self):
     for compiler in [EMCC, EMXX]:
       shortcompiler = os.path.basename(compiler)

tools/shared.py

@@ -178,6 +178,50 @@ def check_call(cmd, *args, **kw):
     raise FatalError("'%s' failed" % " ".join(cmd))
 
 
+def generate_config(path, first_time=False):
+  # Note: repr is used to ensure the paths are escaped correctly on Windows.
+  # The full string is replaced so that the template stays valid Python.
+  config_file = open(path_from_root('tools', 'settings_template_readonly.py')).read().split('\n')
+  config_file = config_file[1:] # remove "this file will be copied..."
+  config_file = '\n'.join(config_file)
+  # autodetect some default paths
+  config_file = config_file.replace('\'{{{ EMSCRIPTEN_ROOT }}}\'', repr(__rootpath__))
+  llvm_root = os.path.dirname(find_executable('llvm-dis') or '/usr/bin/llvm-dis')
+  config_file = config_file.replace('\'{{{ LLVM_ROOT }}}\'', repr(llvm_root))
+
+  node = find_executable('nodejs') or find_executable('node') or 'node'
+  config_file = config_file.replace('\'{{{ NODE }}}\'', repr(node))
+  if WINDOWS:
+    tempdir = os.environ.get('TEMP') or os.environ.get('TMP') or 'c:\\temp'
+  else:
+    tempdir = '/tmp'
+  config_file = config_file.replace('\'{{{ TEMP }}}\'', repr(tempdir))
+
+  abspath = os.path.abspath(os.path.expanduser(path))
+  # write
+  open(abspath, 'w').write(config_file)
+  if first_time:
+    print('''
+==============================================================================
+Welcome to Emscripten!
+
+This is the first time any of the Emscripten tools has been run.
+
+A settings file has been copied to %s, at absolute path: %s
+
+It contains our best guesses for the important paths, which are:
+
+  LLVM_ROOT       = %s
+  NODE_JS         = %s
+  EMSCRIPTEN_ROOT = %s
+
+Please edit the file if any of those are incorrect.
+
+This command will now exit. When you are done editing those paths, re-run it.
+==============================================================================
+''' % (path, abspath, llvm_root, node, __rootpath__), file=sys.stderr)
+
+
 # Emscripten configuration is done through the --em-config command line option or
 # the EM_CONFIG environment variable. If the specified string value contains newline
 # or semicolon-separated definitions, then these definitions will be used to configure
@@ -220,45 +264,7 @@ def check_call(cmd, *args, **kw):
   CONFIG_FILE = os.path.expanduser(EM_CONFIG)
   logging.debug('EM_CONFIG is located in ' + CONFIG_FILE)
   if not os.path.exists(CONFIG_FILE):
-    # Note: repr is used to ensure the paths are escaped correctly on Windows.
-    # The full string is replaced so that the template stays valid Python.
-    config_file = open(path_from_root('tools', 'settings_template_readonly.py')).read().split('\n')
-    config_file = config_file[1:] # remove "this file will be copied..."
-    config_file = '\n'.join(config_file)
-    # autodetect some default paths
-    config_file = config_file.replace('\'{{{ EMSCRIPTEN_ROOT }}}\'', repr(__rootpath__))
-    llvm_root = os.path.dirname(find_executable('llvm-dis') or '/usr/bin/llvm-dis')
-    config_file = config_file.replace('\'{{{ LLVM_ROOT }}}\'', repr(llvm_root))
-
-    node = find_executable('nodejs') or find_executable('node') or 'node'
-    config_file = config_file.replace('\'{{{ NODE }}}\'', repr(node))
-    if WINDOWS:
-      tempdir = os.environ.get('TEMP') or os.environ.get('TMP') or 'c:\\temp'
-    else:
-      tempdir = '/tmp'
-    config_file = config_file.replace('\'{{{ TEMP }}}\'', repr(tempdir))
-
-    # write
-    open(CONFIG_FILE, 'w').write(config_file)
-    print('''
-==============================================================================
-Welcome to Emscripten!
-
-This is the first time any of the Emscripten tools has been run.
-
-A settings file has been copied to %s, at absolute path: %s
-
-It contains our best guesses for the important paths, which are:
-
-  LLVM_ROOT       = %s
-  NODE_JS         = %s
-  EMSCRIPTEN_ROOT = %s
-
-Please edit the file if any of those are incorrect.
-
-This command will now exit. When you are done editing those paths, re-run it.
-==============================================================================
-''' % (EM_CONFIG, CONFIG_FILE, llvm_root, node, __rootpath__), file=sys.stderr)
+    generate_config(EM_CONFIG, first_time=True)
     sys.exit(0)
 
 # The following globals can be overridden by the config file.