pep257.py

#!/usr/bin/env python

"""Static analysis tool for checking docstring conventions and style.

About
-----

Currently implemented checks cover most of PEP257:
http://www.python.org/dev/peps/pep-0257/

After PEP257 is covered and tested, other checks might be added,
e.g. NumPy docstring conventions is the first candidate:
https://github.com/numpy/numpy/blob/master/doc/HOWTO_DOCUMENT.rst.txt

The main repository of this program is located at:
http://github.com/halst/pep257

Creating own checks
-------------------

In order to add your own check, create a function in "Checks functions"
section below. The function should take 3 parameters:

docstring : str
    Docstring to check, as it is in file (with quotes).
context : str
    Docstring's context (e.g. function's source code).
is_script : bool
    Whether the docstring is script with #! or not.

Depending on 1st parameter name, the function will be called with
different type of docstring:

 * module_docstring
 * function_docstring
 * class_docstring
 * method_docstring
 * def_docstring (i.e. function-docstrings + method-docstrings)
 * docstring (i.e. all above docstring types)

E.g. the following function will be fed only class-docstrings:

    def your_check(class_docstring, context, is_script):
        pass

If for a certain function, class, etc. a docstring does not exist,
then `None` will be passed, which should be taken into account.

In order to signify a failure of the check, return a tuple consisting
of (error_message, start_pos, end_pos), where start and end positions
are integers specifying where in *context* the failure occured.
The start_pos and end_pos will be then automatically converted to
be shown correctly, e.g.:

    return "Rasing `IOError` is not documented.", 150, 160

You can skip start/end position; the start/end of docstring will
be used:

    return "Not all parameters mentioned.",

Note the trailing comma! It signifies that return value is
a tuple with 1 element.

Also, see examples in "Check functions" section.

"""

import re
import inspect
from curses.ascii import isascii
try:
    from StringIO import StringIO
except ImportError:
    # python 3.0 and later
    from io import StringIO
from optparse import OptionParser
import tokenize as tk


try:
    all
    any
except NameError:
    # python 2.4 and earlier
    def all(iterable):
        for element in iterable:
            if not element:
                return False
        return True

    def any(iterable):
        for element in iterable:
            if element:
                return True
        return False


try:
    next
except NameError:
    # python 2.5 and earlier
    def next(obj):
        return obj.next()


#
# Helper functions
#


def yield_list(f):
    return lambda *arg, **kw: list(f(*arg, **kw))


def remove_comments(s):
    return re.sub('#[^\n]', '', s)


def abs_pos(marker, source):
    """Return absolute position in source given (line, character) marker."""
    line, char = marker
    lines = StringIO(source).readlines()
    return len(''.join(lines[:line - 1])) + char


def rel_pos(abs_pos, source):
    """Return relative position (line, character) in source based."""
    lines = StringIO(source).readlines()
    assert len(''.join(lines)) >= abs_pos
    while len(''.join(lines)) > abs_pos:
        assert len(''.join(lines)) >= abs_pos
        lines.pop()
    return len(lines) + 1, abs_pos - len(''.join(lines))


#
# Parsing
#


def parse_module_docstring(source):
    for kind, value, _, _, _ in tk.generate_tokens(StringIO(source).readline):
        if kind in [tk.COMMENT, tk.NEWLINE, tk.NL]:
            continue
        elif kind == tk.STRING:
            docstring = value
            return docstring
        else:
            return


def parse_docstring(source, what=''):
    """Parse docstring given `def` or `class` source."""
    if what.startswith('module'):
        return parse_module_docstring(source)
    token_gen = tk.generate_tokens(StringIO(source).readline)
    try:
        kind = None
        while kind != tk.INDENT:
            kind, _, _, _, _ = next(token_gen)
        kind, value, _, _, _ = next(token_gen)
        if kind == tk.STRING:
            return value
    except StopIteration:
        pass


@yield_list
def parse_top_level(source, keyword):
    """Parse top-level functions or classes."""
    token_gen = tk.generate_tokens(StringIO(source).readline)
    kind, value, char = None, None, None
    while True:
        start, end = None, None
        while not (kind == tk.NAME and value == keyword and char == 0):
            kind, value, (line, char), _, _ = next(token_gen)
        start = line, char
        while not (kind == tk.DEDENT and value == '' and char == 0):
            kind, value, (line, char), _, _ = next(token_gen)
        end = line, char
        yield source[abs_pos(start, source): abs_pos(end, source)]


def parse_functions(source):
    return parse_top_level(source, 'def')


def parse_classes(source):
    return parse_top_level(source, 'class')


def skip_indented_block(token_gen):
    kind, value, start, end, raw = next(token_gen)
    while kind != tk.INDENT:
        kind, value, start, end, raw = next(token_gen)
    indent = 1
    for kind, value, start, end, raw in token_gen:
        if kind == tk.INDENT:
            indent += 1
        elif kind == tk.DEDENT:
            indent -= 1
        if indent == 0:
            return kind, value, start, end, raw


@yield_list
def parse_methods(source):
    source = ''.join(parse_classes(source))
    token_gen = tk.generate_tokens(StringIO(source).readline)
    kind, value, char = None, None, None
    while True:
        start, end = None, None
        while not (kind == tk.NAME and value == 'def'):
            kind, value, (line, char), _, _ = next(token_gen)
        start = line, char
        kind, value, (line, char), _, _ = skip_indented_block(token_gen)
        end = line, char
        yield source[abs_pos(start, source): abs_pos(end, source)]


def parse_contexts(source, kind):
    if kind == 'module_docstring':
        return [source]
    if kind == 'function_docstring':
        return parse_functions(source)
    if kind == 'class_docstring':
        return parse_classes(source)
    if kind == 'method_docstring':
        return parse_methods(source)
    if kind == 'def_docstring':
        return parse_functions(source) + parse_methods(source)
    if kind == 'docstring':
        return ([source] + parse_functions(source) +
                parse_classes(source) + parse_methods(source))


#
# Framework
#


class Error(object):

    """Error in docstring style.

    * Stores relevant data about the error,
    * provides format for printing an error,
    * provides __lt__ method to sort errors.

    """

    options = None  # optparse options that define how errors are printed

    def __init__(self, filename, source, docstring, context,
                 explanation, message, start=None, end=None):
        self.filename = filename.split('/')[-1]
        self.source = source
        self.docstring = docstring
        self.context = context
        self.message = message
        self.explanation = explanation

        if start is None:
            self.start = source.find(context) + context.find(docstring)
        else:
            self.start = source.find(context) + start
        self.line, self.char = rel_pos(self.start, self.source)

        if end is None:
            self.end = self.start + len(docstring)
        else:
            self.end = source.find(context) + end
        self.end_line, self.end_char = rel_pos(self.end, self.source)

    def __str__(self):
        s = self.filename + ':%d:%d' % (self.line, self.char)
        if self.options.range:
            s += '..%d:%d' % (self.end_line, self.end_char)
        s += ': ' + self.message
        if self.options.explain:
            s += '\n' + self.explanation
        if self.options.quote:
            s += '\n    ' + self.source[self.start:self.end]
        return s

    def __lt__(self, other):
        return (self.filename, self.start) < (other.filename, other.start)


@yield_list
def find_checks(keyword):
    for function in globals().values():
        if inspect.isfunction(function):
            args = inspect.getargspec(function)[0]
            if args and args[0] == keyword:
                yield function


@yield_list
def check_source(source, filename=''):
    keywords = ['module_docstring', 'function_docstring',
                'class_docstring', 'method_docstring',
                'def_docstring', 'docstring']  # TODO? 'nested_docstring']
    is_script = source.startswith('#!') or filename.startswith('test_')
    for keyword in keywords:
        for check in find_checks(keyword):
            for context in parse_contexts(source, keyword):
                docstring = parse_docstring(context, keyword)
                result = check(docstring, context, is_script)
                if result is not None:
                    yield Error(filename, source, docstring, context,
                                check.__doc__, *result)


def parse_options():
    parser = OptionParser()
    parser.add_option('-e', '--explain', action='store_true',
                      help='show explanation of each error')
    parser.add_option('-r', '--range', action='store_true',
                      help='show error start..end positions')
    parser.add_option('-q', '--quote', action='store_true',
                      help='quote erroneous lines')
    return parser.parse_args()


def main(options, arguments):
    print('=' * 80)
    print('Note: checks are relaxed for scripts (with #!) compared to modules.')
    Error.options = options
    errors = []
    for filename in arguments:
        try:
            errors.extend(check_source(open(filename).read(), filename))
        except IOError:
            print "Error opening file %s" % filename
    for error in sorted(errors):
        print(error)


#
# Check functions
#


def check_modules_have_docstrings(module_docstring, context, is_script):
    """PEP257 Modules should have docstrings.

    All modules should normally have docstrings.

    """
    if not module_docstring:  # or not eval(module_docstring).strip():
        return ("PEP257 Modules should have docstrings.",
                0, min(79, len(context)))
    if not eval(module_docstring).strip():
        return "PEP257 Modules should have docstrings.",


def check_def_has_docstring(def_docstring, context, is_script):
    """PEP257 Exported definitions should have docstrings.

    ...all functions and classes exported by a module should also have
    docstrings. Public methods (including the __init__ constructor)
    should also have docstrings.

    """
    if is_script:
        return  # assume nothing is exported
    def_name = context.split()[1]
    if def_name.startswith('_') and not def_name.endswith('__'):
        return  # private, not exported
    if not def_docstring:
        return ("PEP257 Exported definitions should have docstrings.",
                0, len(context.split('\n')[0]))
    if not eval(def_docstring).strip():
        return "PEP257 Exported definitions should have docstrings.",


def check_class_has_docstring(class_docstring, context, is_script):
    """PEP257 Exported classes should have docstrings.

    ...all functions and classes exported by a module should also have
    docstrings.

    """
    if is_script:
        return  # assume nothing is exported
    class_name = context.split()[1]
    if class_name.startswith('_'):
        return  # not exported
    if not class_docstring:
        return ("PEP257 Exported classes should have docstrings.",
                0, len(context.split('\n')[0]))
    if not eval(class_docstring).strip():
        return "PEP257 Exported classes should have docstrings.",


def check_tripple_double_quotes(docstring, context, is_script):
    '''PEP257 Use """tripple double quotes""".

    For consistency, always use """triple double quotes""" around
    docstrings. Use r"""raw triple double quotes""" if you use any
    backslashes in your docstrings. For Unicode docstrings, use
    u"""Unicode triple-quoted strings""".

    '''
    if docstring and not (docstring.startswith('"""') or
                          docstring.startswith('r"""') or
                          docstring.startswith('u"""')):
        return 'PEP257 Use """tripple double quotes""".',


def check_backslashes(docstring, context, is_script):
    '''PEP257 Use r""" if any backslashes in your docstrings.

    Use r"""raw triple double quotes""" if you use any backslashes (\)
    in your docstrings.

    '''
    if docstring and "\\" in docstring and not docstring.startswith('r"""'):
        return 'PEP257 Use r""" if any backslashes in your docstrings.',


def check_unicode_docstring(docstring, context, is_script):
    '''PEP257 Use u""" for Unicode docstrings.

    For Unicode docstrings, use u"""Unicode triple-quoted strings""".

    '''
    if (docstring and not all(isascii(char) for char in docstring) and
            not docstring.startswith('u"""')):
        return 'PEP257 Use u""" for Unicode docstrings.',


def check_one_liners(docstring, context, is_script):
    """PEP257 One-liners should fit on one line with quotes.

    The closing quotes are on the same line as the opening quotes.
    This looks better for one-liners.

    """
    if not docstring:
        return
    lines = docstring.split('\n')
    if len(lines) > 1:
        non_empty = [l for l in lines if any([c.isalpha() for c in l])]
        if len(non_empty) == 1:
            return "PEP257 One-liners should fit on one line with quotes.",


def check_no_blank_before(def_docstring, context, is_script):
    """PEP257 No blank line before docstring in definitions.

    There's no blank line either before or after the docstring.

    """
    if not def_docstring:
        return
    before = remove_comments(context.split(def_docstring)[0])
    if before.split(':')[-1].count('\n') > 1:
        return "PEP257 No blank line before docstring in definitions.",


def check_ends_with_period(docstring, context, is_script):
    """PEP257 First line should end with a period

    The [first line of a] docstring is a phrase ending in a period.

    """
    if docstring and not eval(docstring).split('\n')[0].strip().endswith('.'):
        return "PEP257 Short description should end with a period.",


def check_imperative_mood(def_docstring, context, is_script):
    """PEP257 First line should be in imperative mood ('Do', not 'Does').

    [Docstring] prescribes the function or method's effect as a command:
    ("Do this", "Return that"), not as a description; e.g. don't write
    "Returns the pathname ...".

    """
    if def_docstring and eval(def_docstring).strip():
        first_word = eval(def_docstring).strip().split()[0]
        if first_word.endswith('s') and not first_word.endswith('ss'):
            return ("PEP257 First line should be in imperative mood "
                    "('Do', not 'Does').",)


def check_no_signature(def_docstring, context, is_script):
    """PEP257 First line should not be function's or method's "signature".

    The one-line docstring should NOT be a "signature" reiterating
    the function/method parameters (which can be obtained by introspection).

    """
    if not def_docstring:
        return
    def_name = context.split(def_docstring)[0].split()[1].split('(')[0]
    first_line = eval(def_docstring).split('\n')[0]
    if def_name + '(' in first_line.replace(' ', ''):
        return "PEP257 First line should not be definitions's \"signature\".",


def check_return_type(def_docstring, context, is_script):
    """PEP257 Return value type should be mentioned.

    However, the nature of the return value cannot be determined by
    introspection, so it should be mentioned.

    """
    if (not def_docstring) or is_script:
        return
    if 'return' not in def_docstring.lower():
        tokens = list(tk.generate_tokens(StringIO(context).readline))
        after_return = [tokens[i + 1][0] for i, token in enumerate(tokens)
                        if token[1] == 'return']
        # not very precise (tk.OP ';' is not taken into account)
        if set(after_return) - set([tk.COMMENT, tk.NL, tk.NEWLINE]) != set([]):
            return "PEP257 Return value type should be mentioned.",


def check_blank_after_summary(docstring, context, is_script):
    """PEP257 Blank line missing after one-line summary.
    ....................
    Multi-line docstrings consist of a summary line just like a one-line
    docstring, followed by a blank line, followed by a more elaborate
    description. The summary line may be used by automatic indexing tools;
    it is important that it fits on one line and is separated from the
    rest of the docstring by a blank line.

    """
    if not docstring:
        return
    lines = eval(docstring).split('\n')
    if len(lines) > 1 and lines[1].strip() != '':
        return "PEP257 Blank line missing after one-line summary.",


def check_indent(docstring, context, is_script):
    """PEP257 Docstrings should be indented same as code.

  The entire docstring is indented the same as the quotes at its
  first line.

    """
    if (not docstring) or len(eval(docstring).split('\n')) == 1:
        return
    non_empty_lines = [line for line in eval(docstring).split('\n')[1:]
                       if line.strip()]
    if not non_empty_lines:
        return
    indent = min([len(l) - len(l.lstrip()) for l in non_empty_lines])
    if indent != len(context.split(docstring)[0].split('\n')[-1]):
        return "PEP257 Docstrings should be indented same as code.",


def check_blank_before_after_class(class_docstring, context, is_script):
    """PEP257 Class docstring should have 1 blank line around them.

    Insert a blank line before and after all docstrings (one-line or
    multi-line) that document a class -- generally speaking, the class's
    methods are separated from each other by a single blank line, and the
    docstring needs to be offset from the first method by a blank line;
    for symmetry, put a blank line between the class header and the
    docstring.

    """
    if not class_docstring:
        return
    before, after = context.split(class_docstring)
    before_blanks = [not line.strip() for line in before.split('\n')]
    after_blanks = [not line.strip() for line in after.split('\n')]
    if before_blanks[-3:] != [False, True, True]:
        return "PEP257 Class docstring should have 1 blank line around them.",
    if after_blanks[:3] != [True, True, False]:
        return "PEP257 Class docstring should have 1 blank line around them.",


def check_blank_after_last_paragtaph(docstring, context, is_script):
    """PEP257 Multiline docstring should end with 1 blank line.

    The BDFL recommends inserting a blank line between the last
    paragraph in a multi-line docstring and its closing quotes,
    placing the closing quotes on a line by themselves.
    """
    if (not docstring) or len(eval(docstring).split('\n')) == 1:
        return
    blanks = [not line.strip() for line in eval(docstring).split('\n')]
    if blanks[-3:] != [False, True, True]:
        return "PEP257 Multiline docstring should end with 1 blank line.",


if __name__ == '__main__':
    try:
        main(*parse_options())
    except KeyboardInterrupt:
        pass