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# ast.py
# Copyright (C) 2006 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of Mako and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""utilities for analyzing expressions and blocks of Python code, as well as generating Python from AST nodes"""
from compiler import ast, visitor
from compiler import parse as compiler_parse
from mako import util, exceptions
from StringIO import StringIO
import re
def parse(code, mode, lineno, pos, filename):
try:
return compiler_parse(code, mode)
except SyntaxError, e:
raise exceptions.SyntaxException("(%s) %s (%s)" % (e.__class__.__name__, str(e), repr(code[0:50])), lineno, pos, filename)
class PythonCode(object):
"""represents information about a string containing Python code"""
def __init__(self, code, lineno, pos, filename):
self.code = code
# represents all identifiers which are assigned to at some point in the code
self.declared_identifiers = util.Set()
# represents all identifiers which are referenced before their assignment, if any
self.undeclared_identifiers = util.Set()
# note that an identifier can be in both the undeclared and declared lists.
# using AST to parse instead of using code.co_varnames, code.co_names has several advantages:
# - we can locate an identifier as "undeclared" even if its declared later in the same block of code
# - AST is less likely to break with version changes (for example, the behavior of co_names changed a little bit
# in python version 2.5)
if isinstance(code, basestring):
expr = parse(code.lstrip(), "exec", lineno, pos, filename)
else:
expr = code
class FindIdentifiers(object):
def visitAssName(s, node, *args):
# if node.name not in self.undeclared_identifiers:
self.declared_identifiers.add(node.name)
def visitAssign(s, node, *args):
# flip around the visiting of Assign so the expression gets evaluated first,
# in the case of a clause like "x=x+5" (x is undeclared)
s.visit(node.expr, *args)
for n in node.nodes:
s.visit(n, *args)
def visitFunction(s,node, *args):
# just need the function name. the contents of it are local to the function, dont parse those.
# TODO: parse the default values in the functions keyword arguments.
self.declared_identifiers.add(node.name)
def visitFor(s, node, *args):
# flip around visit
s.visit(node.list, *args)
s.visit(node.assign, *args)
s.visit(node.body, *args)
def visitTryExcept(s, node, *args):
for (decl, s2, s3) in node.handlers:
if decl is not None:
(exception, ident) = [n.name for n in decl.nodes]
self.declared_identifiers.add(ident)
def visitName(s, node, *args):
if node.name not in __builtins__ and node.name not in self.declared_identifiers:
self.undeclared_identifiers.add(node.name)
def visitImport(s, node, *args):
for (mod, alias) in node.names:
if alias is not None:
self.declared_identifiers.add(alias)
else:
self.declared_identifiers.add(mod)
def visitFrom(s, node, *args):
for (mod, alias) in node.names:
if alias is not None:
self.declared_identifiers.add(alias)
else:
if mod == '*':
raise exceptions.CompileException("'import *' is not supported, since all identifier names must be explicitly declared. Please use the form 'from <modulename> import <name1>, <name2>, ...' instead.", lineno, pos, filename)
self.declared_identifiers.add(mod)
f = FindIdentifiers()
visitor.walk(expr, f) #, walker=walker())
class ArgumentList(object):
"""parses a fragment of code as a comma-separated list of expressions"""
def __init__(self, code, lineno, pos, filename):
self.codeargs = []
self.args = []
self.declared_identifiers = util.Set()
self.undeclared_identifiers = util.Set()
class FindTuple(object):
def visitTuple(s, node, *args):
for n in node.nodes:
p = PythonCode(n, lineno, pos, filename)
self.codeargs.append(p)
self.args.append(ExpressionGenerator(n).value())
self.declared_identifiers = self.declared_identifiers.union(p.declared_identifiers)
self.undeclared_identifiers = self.undeclared_identifiers.union(p.undeclared_identifiers)
if isinstance(code, basestring):
if re.match(r"\S", code) and not re.match(r",\s*$", code):
# if theres text and no trailing comma, insure its parsed
# as a tuple by adding a trailing comma
code += ","
expr = parse(code, "exec", lineno, pos, filename)
else:
expr = code
f = FindTuple()
visitor.walk(expr, f)
class PythonFragment(PythonCode):
"""extends PythonCode to provide identifier lookups in partial control statements
e.g.
for x in 5:
elif y==9:
except (MyException, e):
etc.
"""
def __init__(self, code, lineno, pos, filename):
m = re.match(r'^(\w+)(?:\s+(.*?))?:$', code.strip())
if not m:
raise exceptions.CompileException("Fragment '%s' is not a partial control statement" % code, lineno, pos, filename)
(keyword, expr) = m.group(1,2)
if keyword in ['for','if', 'while']:
code = code + "pass"
elif keyword == 'try':
code = code + "pass\nexcept:pass"
elif keyword == 'elif' or keyword == 'else':
code = "if False:pass\n" + code + "pass"
elif keyword == 'except':
code = "try:pass\n" + code + "pass"
else:
raise exceptions.CompileException("Unsupported control keyword: '%s'" % keyword, lineno, pos, filename)
super(PythonFragment, self).__init__(code, lineno, pos, filename)
class walker(visitor.ASTVisitor):
def dispatch(self, node, *args):
print "Node:", str(node)
#print "dir:", dir(node)
return visitor.ASTVisitor.dispatch(self, node, *args)
class FunctionDecl(object):
"""function declaration"""
def __init__(self, code, lineno, pos, filename):
self.code = code
expr = parse(code, "exec", lineno, pos, filename)
class ParseFunc(object):
def visitFunction(s, node, *args):
self.funcname = node.name
self.argnames = node.argnames
self.defaults = node.defaults
self.varargs = node.varargs
self.kwargs = node.kwargs
f = ParseFunc()
visitor.walk(expr, f)
if not hasattr(self, 'funcname'):
raise exceptions.CompileException("Code '%s' is not a function declaration" % code, lineno, pos, filename)
def get_argument_expressions(self, include_defaults=True):
"""return the argument declarations of this FunctionDecl as a printable list."""
namedecls = []
defaults = [d for d in self.defaults]
kwargs = self.kwargs
varargs = self.varargs
argnames = [f for f in self.argnames]
argnames.reverse()
for arg in argnames:
default = None
if kwargs:
arg = "**" + arg
kwargs = False
elif varargs:
arg = "*" + arg
varargs = False
else:
default = len(defaults) and defaults.pop() or None
if include_defaults and default:
namedecls.insert(0, "%s=%s" % (arg, ExpressionGenerator(default).value()))
else:
namedecls.insert(0, arg)
return namedecls
class FunctionArgs(FunctionDecl):
"""the argument portion of a function declaration"""
def __init__(self, code, lineno, pos, filename):
super(FunctionArgs, self).__init__("def ANON(%s):pass" % code, lineno, pos, filename)
class ExpressionGenerator(object):
"""given an AST node, generates an equivalent literal Python expression."""
def __init__(self, astnode):
self.buf = StringIO()
visitor.walk(astnode, self) #, walker=walker())
def value(self):
return self.buf.getvalue()
def operator(self, op, node, *args):
self.buf.write("(")
self.visit(node.left, *args)
self.buf.write(" %s " % op)
self.visit(node.right, *args)
self.buf.write(")")
def visitConst(self, node, *args):
self.buf.write(repr(node.value))
def visitName(self, node, *args):
self.buf.write(node.name)
def visitMul(self, node, *args):
self.operator("*", node, *args)
def visitAdd(self, node, *args):
self.operator("+", node, *args)
def visitGetattr(self, node, *args):
self.visit(node.expr, *args)
self.buf.write(".%s" % node.attrname)
def visitSub(self, node, *args):
self.operator("-", node, *args)
def visitDiv(self, node, *args):
self.operator("/", node, *args)
def visitSubscript(self, node, *args):
self.visit(node.expr)
self.buf.write("[")
[self.visit(x) for x in node.subs]
self.buf.write("]")
def visitSlice(self, node, *args):
self.visit(node.expr)
self.buf.write("[")
if node.lower is not None:
self.visit(node.lower)
self.buf.write(":")
if node.upper is not None:
self.visit(node.upper)
self.buf.write("]")
def visitCallFunc(self, node, *args):
self.visit(node.node)
self.buf.write("(")
self.visit(node.args[0])
for a in node.args[1:]:
self.buf.write(", ")
self.visit(a)
self.buf.write(")")
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