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comment_eater.py
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Mon, Jul 1, 16:05

comment_eater.py
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from cStringIO import StringIO
import compiler
import inspect
import textwrap
import tokenize
from compiler_unparse import unparse
class Comment(object):
""" A comment block.
"""
is_comment = True
def __init__(self, start_lineno, end_lineno, text):
# int : The first line number in the block. 1-indexed.
self.start_lineno = start_lineno
# int : The last line number. Inclusive!
self.end_lineno = end_lineno
# str : The text block including '#' character but not any leading spaces.
self.text = text
def add(self, string, start, end, line):
""" Add a new comment line.
"""
self.start_lineno = min(self.start_lineno, start[0])
self.end_lineno = max(self.end_lineno, end[0])
self.text += string
def __repr__(self):
return '%s(%r, %r, %r)' % (self.__class__.__name__, self.start_lineno,
self.end_lineno, self.text)
class NonComment(object):
""" A non-comment block of code.
"""
is_comment = False
def __init__(self, start_lineno, end_lineno):
self.start_lineno = start_lineno
self.end_lineno = end_lineno
def add(self, string, start, end, line):
""" Add lines to the block.
"""
if string.strip():
# Only add if not entirely whitespace.
self.start_lineno = min(self.start_lineno, start[0])
self.end_lineno = max(self.end_lineno, end[0])
def __repr__(self):
return '%s(%r, %r)' % (self.__class__.__name__, self.start_lineno,
self.end_lineno)
class CommentBlocker(object):
""" Pull out contiguous comment blocks.
"""
def __init__(self):
# Start with a dummy.
self.current_block = NonComment(0, 0)
# All of the blocks seen so far.
self.blocks = []
# The index mapping lines of code to their associated comment blocks.
self.index = {}
def process_file(self, file):
""" Process a file object.
"""
for token in tokenize.generate_tokens(file.next):
self.process_token(*token)
self.make_index()
def process_token(self, kind, string, start, end, line):
""" Process a single token.
"""
if self.current_block.is_comment:
if kind == tokenize.COMMENT:
self.current_block.add(string, start, end, line)
else:
self.new_noncomment(start[0], end[0])
else:
if kind == tokenize.COMMENT:
self.new_comment(string, start, end, line)
else:
self.current_block.add(string, start, end, line)
def new_noncomment(self, start_lineno, end_lineno):
""" We are transitioning from a noncomment to a comment.
"""
block = NonComment(start_lineno, end_lineno)
self.blocks.append(block)
self.current_block = block
def new_comment(self, string, start, end, line):
""" Possibly add a new comment.
Only adds a new comment if this comment is the only thing on the line.
Otherwise, it extends the noncomment block.
"""
prefix = line[:start[1]]
if prefix.strip():
# Oops! Trailing comment, not a comment block.
self.current_block.add(string, start, end, line)
else:
# A comment block.
block = Comment(start[0], end[0], string)
self.blocks.append(block)
self.current_block = block
def make_index(self):
""" Make the index mapping lines of actual code to their associated
prefix comments.
"""
for prev, block in zip(self.blocks[:-1], self.blocks[1:]):
if not block.is_comment:
self.index[block.start_lineno] = prev
def search_for_comment(self, lineno, default=None):
""" Find the comment block just before the given line number.
Returns None (or the specified default) if there is no such block.
"""
if not self.index:
self.make_index()
block = self.index.get(lineno, None)
text = getattr(block, 'text', default)
return text
def strip_comment_marker(text):
""" Strip # markers at the front of a block of comment text.
"""
lines = []
for line in text.splitlines():
lines.append(line.lstrip('#'))
text = textwrap.dedent('\n'.join(lines))
return text
def get_class_traits(klass):
""" Yield all of the documentation for trait definitions on a class object.
"""
# FIXME: gracefully handle errors here or in the caller?
source = inspect.getsource(klass)
cb = CommentBlocker()
cb.process_file(StringIO(source))
mod_ast = compiler.parse(source)
class_ast = mod_ast.node.nodes[0]
for node in class_ast.code.nodes:
# FIXME: handle other kinds of assignments?
if isinstance(node, compiler.ast.Assign):
name = node.nodes[0].name
rhs = unparse(node.expr).strip()
doc = strip_comment_marker(cb.search_for_comment(node.lineno, default=''))
yield name, rhs, doc

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