"""Generate ast module from specification
This script generates the ast module from a simple specification,
which makes it easy to accomodate changes in the grammar. This
approach would be quite reasonable if the grammar changed often.
Instead, it is rather complex to generate the appropriate code. And
the Node interface has changed more often than the grammar.
"""
import fileinput
import re
import sys
from StringIO import StringIO
SPEC = "ast.txt"
COMMA = ", "
def load_boilerplate(file):
f = open(file)
buf = f.read()
f.close()
i = buf.find('### ''PROLOGUE')
j = buf.find('### ''EPILOGUE')
pro = buf[i+12:j].strip()
epi = buf[j+12:].strip()
return pro, epi
def strip_default(arg):
"""Return the argname from an 'arg = default' string"""
i = arg.find('=')
if i == -1:
return arg
t = arg[:i].strip()
return t
P_NODE = 1
P_OTHER = 2
P_NESTED = 3
P_NONE = 4
class NodeInfo:
"""Each instance describes a specific AST node"""
def __init__(self, name, args):
self.name = name
self.args = args.strip()
self.argnames = self.get_argnames()
self.argprops = self.get_argprops()
self.nargs = len(self.argnames)
self.init = []
def get_argnames(self):
if '(' in self.args:
i = self.args.find('(')
j = self.args.rfind(')')
args = self.args[i+1:j]
else:
args = self.args
return [strip_default(arg.strip())
for arg in args.split(',') if arg]
def get_argprops(self):
"""Each argument can have a property like '*' or '!'
XXX This method modifies the argnames in place!
"""
d = {}
hardest_arg = P_NODE
for i in range(len(self.argnames)):
arg = self.argnames[i]
if arg.endswith('*'):
arg = self.argnames[i] = arg[:-1]
d[arg] = P_OTHER
hardest_arg = max(hardest_arg, P_OTHER)
elif arg.endswith('!'):
arg = self.argnames[i] = arg[:-1]
d[arg] = P_NESTED
hardest_arg = max(hardest_arg, P_NESTED)
elif arg.endswith('&'):
arg = self.argnames[i] = arg[:-1]
d[arg] = P_NONE
hardest_arg = max(hardest_arg, P_NONE)
else:
d[arg] = P_NODE
self.hardest_arg = hardest_arg
if hardest_arg > P_NODE:
self.args = self.args.replace('*', '')
self.args = self.args.replace('!', '')
self.args = self.args.replace('&', '')
return d
def gen_source(self):
buf = StringIO()
print >> buf, "class %s(Node):" % self.name
self._gen_init(buf)
print >> buf
self._gen_getChildren(buf)
print >> buf
self._gen_getChildNodes(buf)
print >> buf
self._gen_repr(buf)
buf.seek(0, 0)
return buf.read()
def _gen_init(self, buf):
if self.args:
print >> buf, " def __init__(self, %s, lineno=None):" % self.args
else:
print >> buf, " def __init__(self, lineno=None):"
if self.argnames:
for name in self.argnames:
print >> buf, " self.%s = %s" % (name, name)
print >> buf, " self.lineno = lineno"
# Copy the lines in self.init, indented four spaces. The rstrip()
# business is to get rid of the four spaces if line happens to be
# empty, so that reindent.py is happy with the output.
for line in self.init:
print >> buf, (" " + line).rstrip()
def _gen_getChildren(self, buf):
print >> buf, " def getChildren(self):"
if len(self.argnames) == 0:
print >> buf, " return ()"
else:
if self.hardest_arg < P_NESTED:
clist = COMMA.join(["self.%s" % c
for c in self.argnames])
if self.nargs == 1:
print >> buf, " return %s," % clist
else:
print >> buf, " return %s" % clist
else:
if len(self.argnames) == 1:
print >> buf, " return tuple(flatten(self.%s))" % self.argnames[0]
else:
print >> buf, " children = []"
template = " children.%s(%sself.%s%s)"
for name in self.argnames:
if self.argprops[name] == P_NESTED:
print >> buf, template % ("extend", "flatten(",
name, ")")
else:
print >> buf, template % ("append", "", name, "")
print >> buf, " return tuple(children)"
def _gen_getChildNodes(self, buf):
print >> buf, " def getChildNodes(self):"
if len(self.argnames) == 0:
print >> buf, " return ()"
else:
if self.hardest_arg < P_NESTED:
clist = ["self.%s" % c
for c in self.argnames
if self.argprops[c] == P_NODE]
if len(clist) == 0:
print >> buf, " return ()"
elif len(clist) == 1:
print >> buf, " return %s," % clist[0]
else:
print >> buf, " return %s" % COMMA.join(clist)
else:
print >> buf, " nodelist = []"
template = " nodelist.%s(%sself.%s%s)"
for name in self.argnames:
if self.argprops[name] == P_NONE:
tmp = (" if self.%s is not None:\n"
" nodelist.append(self.%s)")
print >> buf, tmp % (name, name)
elif self.argprops[name] == P_NESTED:
print >> buf, template % ("extend", "flatten_nodes(",
name, ")")
elif self.argprops[name] == P_NODE:
print >> buf, template % ("append", "", name, "")
print >> buf, " return tuple(nodelist)"
def _gen_repr(self, buf):
print >> buf, " def __repr__(self):"
if self.argnames:
fmt = COMMA.join(["%s"] * self.nargs)
if '(' in self.args:
fmt = '(%s)' % fmt
vals = ["repr(self.%s)" % name for name in self.argnames]
vals = COMMA.join(vals)
if self.nargs == 1:
vals = vals + ","
print >> buf, ' return "%s(%s)" %% (%s)' % \
(self.name, fmt, vals)
else:
print >> buf, ' return "%s()"' % self.name
rx_init = re.compile('init\((.*)\):')
def parse_spec(file):
classes = {}
cur = None
for line in fileinput.input(file):
if line.strip().startswith('#'):
continue
mo = rx_init.search(line)
if mo is None:
if cur is None:
# a normal entry
try:
name, args = line.split(':')
except ValueError:
continue
classes[name] = NodeInfo(name, args)
cur = None
else:
# some code for the __init__ method
cur.init.append(line)
else:
# some extra code for a Node's __init__ method
name = mo.group(1)
cur = classes[name]
return sorted(classes.values(), key=lambda n: n.name)
def main():
prologue, epilogue = load_boilerplate(sys.argv[-1])
print prologue
print
classes = parse_spec(SPEC)
for info in classes:
print info.gen_source()
print epilogue
if __name__ == "__main__":
main()
sys.exit(0)
### PROLOGUE
"""Python abstract syntax node definitions
This file is automatically generated by Tools/compiler/astgen.py
"""
from consts import CO_VARARGS,CO_VARKEYWORDS
def flatten(seq):
l = []
for elt in seq:
t = type(elt)
if t is tuple or t is list:
for elt2 in flatten(elt):
l.append(elt2)
else:
l.append(elt)
return l
def flatten_nodes(seq):
return [n for n in flatten(seq) if isinstance(n, Node)]
nodes = {}
class Node(object):
"""Abstract base class for ast nodes."""
def getChildren(self):
pass # implemented by subclasses
def __iter__(self):
for n in self.getChildren():
yield n
def asList(self): # for backwards compatibility
return self.getChildren()
def getChildNodes(self):
pass # implemented by subclasses
def _get_lineno(self):
return self._lineno
def _set_lineno(self, lineno):
if lineno is not None and not isinstance(lineno, int):
self._context = lineno
self._lineno = lineno[1][0]
else:
self._lineno = lineno
self._context = None
lineno = property(_get_lineno, _set_lineno)
class EmptyNode(Node):
pass
class Expression(Node):
# Expression is an artificial node class to support "eval"
nodes["expression"] = "Expression"
def __init__(self, node):
Node.__init__(self)
self.node = node
def getChildren(self):
return self.node,
def getChildNodes(self):
return self.node,
def __repr__(self):
return "Expression(%s)" % (repr(self.node))
### EPILOGUE
for name, obj in globals().items():
if isinstance(obj, type) and issubclass(obj, Node):
nodes[name.lower()] = obj
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