Support for embedded .emscripten config

emsdk has always had partial support for this.  With this change all
emscripten users can take advantage of embedded config.  This allows
different emscripten installations to have different configuration files
since they don't need to share a single config file in the user's home
directory.

As a followup and plan to make this location the default when generating
a new sample config file.

See #9543

Author: sbc100

.gitignore

@@ -1,3 +1,8 @@
+# Config file
+.emscripten
+.emscripten_sanity
+.emscripten_sanity_wasm
+
 # vim/emacs temporary/backup files
 *~
 *.swp

ChangeLog.md

@@ -24,6 +24,9 @@ Current Trunk
    unless you use errno defines (like EAGAIN) *and* keep around binaries
    compiled with an older version that you link against. In that case, you
    should rebuild them. See #9545.
+ - Emscripten now supports the config file (.emscripten) being placed in the
+   emscriten directory rather that the current user's home directory.
+   See #9543
 
 v.1.38.46: 09/25/2019
 ---------------------

tools/shared.py

@@ -231,13 +231,19 @@ def generate_config(path, first_time=False):
 ''' % (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
-# Emscripten.  Otherwise, the string is understood to be a path to a settings
-# file that contains the required definitions.
-
-try:
+# 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 Emscripten.  Otherwise, the string is understood to be a
+# path to a settings file that contains the required definitions.
+# The search order from the config file is as follows:
+# 1. Specified on the command line (--em-config)
+# 2. Specified via EM_CONFIG environment variable
+# 3. If emscripen-local .emescripten file is found, use that
+# 4. Fall back users home direcotry (~/.emscripten).
+
+embedded_config = path_from_root('.emscripten')
+if '--em-config' in sys.argv:
   EM_CONFIG = sys.argv[sys.argv.index('--em-config') + 1]
   # And now remove it from sys.argv
   skip = False
@@ -250,22 +256,25 @@ def generate_config(path, first_time=False):
     elif skip:
       skip = False
   sys.argv = newargs
-  # Emscripten compiler spawns other processes, which can reimport shared.py, so make sure that
-  # those child processes get the same configuration file by setting it to the currently active environment.
-  os.environ['EM_CONFIG'] = EM_CONFIG
-except Exception:
-  EM_CONFIG = os.environ.get('EM_CONFIG')
-
-if EM_CONFIG and not os.path.isfile(EM_CONFIG):
-  if EM_CONFIG.startswith('-'):
-    exit_with_error('Passed --em-config without an argument. Usage: --em-config /path/to/.emscripten or --em-config LLVM_ROOT=/path;...')
-  if '=' not in EM_CONFIG:
-    exit_with_error('File ' + EM_CONFIG + ' passed to --em-config does not exist!')
-  else:
-    EM_CONFIG = EM_CONFIG.replace(';', '\n') + '\n'
-
-if not EM_CONFIG:
+  if not os.path.isfile(EM_CONFIG):
+    if EM_CONFIG.startswith('-'):
+      exit_with_error('Passed --em-config without an argument. Usage: --em-config /path/to/.emscripten or --em-config LLVM_ROOT=/path;...')
+    if '=' not in EM_CONFIG:
+      exit_with_error('File ' + EM_CONFIG + ' passed to --em-config does not exist!')
+    else:
+      EM_CONFIG = EM_CONFIG.replace(';', '\n') + '\n'
+elif 'EM_CONFIG' in os.environ:
+  EM_CONFIG = os.environ['EM_CONFIG']
+elif os.path.exists(embedded_config):
+  EM_CONFIG = embedded_config
+else:
   EM_CONFIG = '~/.emscripten'
+
+# Emscripten compiler spawns other processes, which can reimport shared.py, so
+# make sure that those child processes get the same configuration file by
+# setting it to the currently active environment.
+os.environ['EM_CONFIG'] = EM_CONFIG
+
 if '\n' in EM_CONFIG:
   CONFIG_FILE = None
   logger.debug('EM_CONFIG is specified inline without a file')