Use markerlib for markers in 'extras'

CHANGES.txt

@@ -6,6 +6,7 @@ CHANGES
 0.7.2
 -----
 
+* Issue #14: Prefer markerlib for evaluation of marker expressions in extras.
 * Issue #10: ``ez_setup.py`` now uses HTTPS to download setuptools from PyPI.
 
 -----

pkg_resources.py

@@ -1211,86 +1211,16 @@ def invalid_marker(text):
         return sys.exc_info()[1]
     return False
 
-def evaluate_marker(text, extra=None, _ops={}):
+def evaluate_marker(text):
     """Evaluate a PEP 426 environment marker; SyntaxError if marker is invalid"""
-
-    if not _ops:
-
-        from token import NAME, STRING
-        import token, symbol, operator
-
-        def and_test(nodelist):
-            # MUST NOT short-circuit evaluation, or invalid syntax can be skipped!
-            return reduce(operator.and_, [interpret(nodelist[i]) for i in range(1,len(nodelist),2)])
-
-        def test(nodelist):
-            # MUST NOT short-circuit evaluation, or invalid syntax can be skipped!
-            return reduce(operator.or_, [interpret(nodelist[i]) for i in range(1,len(nodelist),2)])
-
-        def atom(nodelist):
-            t = nodelist[1][0]
-            if t == token.LPAR:
-                if nodelist[2][0] == token.RPAR:
-                    raise SyntaxError("Empty parentheses")
-                return interpret(nodelist[2])
-            raise SyntaxError("Language feature not supported in environment markers")
-
-        def comparison(nodelist):
-            if len(nodelist)>4:
-                raise SyntaxError("Chained comparison not allowed in environment markers")
-            comp = nodelist[2][1]
-            cop = comp[1]
-            if comp[0] == NAME:
-                if len(nodelist[2]) == 3:
-                    if cop == 'not':
-                        cop = 'not in'
-                    else:
-                        cop = 'is not'
-            try:
-                cop = _ops[cop]
-            except KeyError:
-                raise SyntaxError(repr(cop)+" operator not allowed in environment markers")
-            return cop(evaluate(nodelist[1]), evaluate(nodelist[3]))
-
-        _ops.update({
-            symbol.test: test, symbol.and_test: and_test, symbol.atom: atom,
-            symbol.comparison: comparison, 'not in': lambda x,y: x not in y,
-            'in': lambda x,y: x in y, '==': operator.eq, '!=': operator.ne,
-        })
-        if hasattr(symbol,'or_test'):
-            _ops[symbol.or_test] = test
-
-    def interpret(nodelist):
-        while len(nodelist)==2: nodelist = nodelist[1]
-        try:
-            op = _ops[nodelist[0]]
-        except KeyError:
-            raise SyntaxError("Comparison or logical expression expected")
-            raise SyntaxError("Language feature not supported in environment markers: "+symbol.sym_name[nodelist[0]])
-        return op(nodelist)
-
-    def evaluate(nodelist):
-        while len(nodelist)==2: nodelist = nodelist[1]
-        kind = nodelist[0]
-        name = nodelist[1]
-        #while len(name)==2: name = name[1]
-        if kind==NAME:
-            try:
-                op = _marker_values[name]
-            except KeyError:
-                raise SyntaxError("Unknown name %r" % name)
-            return op()
-        if kind==STRING:
-            s = nodelist[1]
-            if s[:1] not in "'\"" or s.startswith('"""') or s.startswith("'''") \
-            or '\\' in s:
-                raise SyntaxError(
-                    "Only plain strings allowed in environment markers")
-            return s[1:-1]
-        raise SyntaxError("Language feature not supported in environment markers")
-
-    import parser
-    return interpret(parser.expr(text).totuple(1)[1])
+    import _markerlib
+    # markerlib implements Metadata 1.2 (PEP 345) environment markers.
+    # Translate the variables to Metadata 2.0 (PEP 426).
+    env = _markerlib.default_environment()
+    for key in env.keys():
+        new_key = key.replace('.', '_')
+        env[new_key] = env.pop(key)
+    return _markerlib.interpret(text, env)
 
 
 class NullProvider: