1 """Check for errs in the AST.

     2 

     3 The Python parser does not catch all syntax errors.  Others, like

     4 assignments with invalid targets, are caught in the code generation

     5 phase.

     6 

     7 The compiler package catches some errors in the transformer module.

     8 But it seems clearer to write checkers that use the AST to detect

     9 errors.

    10 """

    11 

    12 from compiler import ast, walk

    13 

    14 def check(tree, multi=None):

    15     v = SyntaxErrorChecker(multi)

    16     walk(tree, v)

    17     return v.errors

    18 

    19 class SyntaxErrorChecker:

    20     """A visitor to find syntax errors in the AST."""

    21 

    22     def __init__(self, multi=None):

    23         """Create new visitor object.

    24 

    25         If optional argument multi is not None, then print messages

    26         for each error rather than raising a SyntaxError for the

    27         first.

    28         """

    29         self.multi = multi

    30         self.errors = 0

    31 

    32     def error(self, node, msg):

    33         self.errors = self.errors + 1

    34         if self.multi is not None:

    35             print "%s:%s: %s" % (node.filename, node.lineno, msg)

    36         else:

    37             raise SyntaxError, "%s (%s:%s)" % (msg, node.filename, node.lineno)

    38 

    39     def visitAssign(self, node):

    40         # the transformer module handles many of these

    41         pass

    42 ##        for target in node.nodes:

    43 ##            if isinstance(target, ast.AssList):

    44 ##                if target.lineno is None:

    45 ##                    target.lineno = node.lineno

    46 ##                self.error(target, "can't assign to list comprehension")