Internal change.

refex/python/evaluate.py

@@ -34,14 +34,11 @@
 
 from refex.python import error_strings
 from refex.python import matcher
-from refex.python import matchers
 from refex.python import semiliteral_eval
-# Actually collect all the matchers into the matchers module, so they can be
-# enumerated.
-import refex.python.matchers.ast_matchers  # pylint: disable=unused-import
-import refex.python.matchers.base_matchers  # pylint: disable=unused-import
-import refex.python.matchers.lexical_matchers  # pylint: disable=unused-import
-import refex.python.matchers.syntax_matchers  # pylint: disable=unused-import
+from refex.python.matchers import ast_matchers
+from refex.python.matchers import base_matchers
+from refex.python.matchers import lexical_matchers
+from refex.python.matchers import syntax_matchers
 
 
 def _sorted_attributes(o):
@@ -50,21 +47,32 @@ def _sorted_attributes(o):
     yield a, getattr(o, a)
 
 
-def _get_matcher_map():
-  """Get the mapping from dotted-names to matcher constructors/callables."""
-  mapping = {}
-  for module_name, module in _sorted_attributes(matchers):
-    for global_variable, value in _sorted_attributes(module):
-      if not isinstance(value, type):
-        continue
-      if not matcher.is_safe_to_eval(value):
-        continue
-      mapping[global_variable] = value
-      mapping['%s.%s' % (module_name, global_variable)] = value
-  return mapping
+# TODO: remove overwrite param
 
 
-_ALL_MATCHERS = _get_matcher_map()
+def add_module(module, overwrite=False):
+  """Adds a non-builtin matcher module to be available for compile_matcher."""
+  for global_variable, value in _sorted_attributes(module):
+    if not isinstance(value, type):
+      continue
+    if not matcher.is_safe_to_eval(value):
+      continue
+
+    is_mutated = False
+    module_name = module.__name__.rsplit('.', 1)[-1]
+    for name in global_variable, f'{module_name}.{global_variable}':
+      if overwrite or name not in _ALL_MATCHERS:
+        _ALL_MATCHERS[name] = value
+        is_mutated = True
+    if not is_mutated:
+      raise ValueError(f'Could not add matcher: f{value!r}')
+
+
+_ALL_MATCHERS = {}
+add_module(ast_matchers, overwrite=True)
+add_module(base_matchers, overwrite=True)
+add_module(lexical_matchers, overwrite=True)
+add_module(syntax_matchers, overwrite=True)
 
 
 def compile_matcher(user_input:str) -> matcher.Matcher: