Lib/compiler/syntax.py

   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         for target in node.nodes:
  42             pass
  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")