IDL parser: fix rebuilding of (stale) cached lexer tables

Source/bindings/scripts/blink_idl_lexer.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 70 matching lines @@
     # Analogs to _AddToken/_AddTokens in base lexer
     # Needed to remove COMMENT token, since comments ignored
     def _RemoveToken(self, token):
         if token in self.tokens:
             self.tokens.remove(token)
 
     def _RemoveTokens(self, tokens):
         for token in tokens:
             self._RemoveToken(token)
 
-    def __init__(self, debug=False, optimize=True, outputdir=None):
+    def __init__(self, debug=False, optimize=True, outputdir=None,
+                 rewrite_tables=False):
         if debug:
             # Turn off optimization and caching to help debugging
             optimize = False
             outputdir = None
         if outputdir:
             # Need outputdir in path because lex imports the cached lex table
             # as a Python module
             sys.path.append(outputdir)
 
+            if rewrite_tables:
+                tablefile = os.path.join(outputdir, 'lextab.py')
+
+                def unlink(filename):
+                    try:
+                        os.unlink(filename)
+                    except OSError:
+                        pass
+
+                unlink(tablefile)

[Nils Barth (inactive), 2014/07/29 16:00:25]

FWIW, cleaner would be a loop through suffixes, which avoids needing a helper
function:

tablefile_root = os.path.join(outputdir, 'lextab')
for ext in ('.py', '.pyc', '.pyo'):
    try:
        os.unlink(tablefile_root + ext)
    except OSError:
        pass

...and to be really formal, we'd want
LEXTAB = 'lextab'
...and to use that both places.
...but that's a *bit* picky.

+                # Also remove the .pyc/.pyo files, or they'll be used even if
+                # the .py file doesn't exist.
+                unlink(tablefile + 'c')
+                unlink(tablefile + 'o')
+
         IDLLexer.__init__(self)
         # Overrides to parent class
         self._RemoveTokens(REMOVE_TOKENS)
         # Optimized mode substantially decreases startup time (by disabling
         # error checking), and also allows use of Python's optimized mode.
         # See: Optimized Mode
         # http://www.dabeaz.com/ply/ply.html#ply_nn15
         self._lexobj = lex.lex(object=self,
                                debug=debug,
                                optimize=optimize,
+                               lextab='lextab',
                                outputdir=outputdir)
 
 
 ################################################################################
 
 def main(argv):
     # If file itself executed, build and cache lex table
     try:
         outputdir = argv[1]
     except IndexError as err:
         print 'Usage: %s OUTPUT_DIR' % argv[0]
         return 1
-    lexer = BlinkIDLLexer(outputdir=outputdir)
+    # Important: rewrite_tables=True causes the cache file to be deleted if it
+    # exists, thus making sure that PLY doesn't load it instead of regenerating
+    # the parse table.
+    lexer = BlinkIDLLexer(outputdir=outputdir, rewrite_tables=True)
 
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))