summaryrefslogtreecommitdiff
path: root/pylint/checkers/design_analysis.py
blob: 0c1a21cb91be3a42b1eecc150bc539cdea892f0f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
# -*- coding: utf-8 -*-
# Copyright (c) 2006, 2009-2010, 2012-2015 LOGILAB S.A. (Paris, FRANCE) <contact@logilab.fr>
# Copyright (c) 2012, 2014 Google, Inc.
# Copyright (c) 2014-2018 Claudiu Popa <pcmanticore@gmail.com>
# Copyright (c) 2014 Arun Persaud <arun@nubati.net>
# Copyright (c) 2015 Ionel Cristian Maries <contact@ionelmc.ro>
# Copyright (c) 2016 Łukasz Rogalski <rogalski.91@gmail.com>
# Copyright (c) 2017 ahirnish <ahirnish@gmail.com>
# Copyright (c) 2018 Mike Frysinger <vapier@gmail.com>
# Copyright (c) 2018 Mark Miller <725mrm@gmail.com>
# Copyright (c) 2018 Ashley Whetter <ashley@awhetter.co.uk>
# Copyright (c) 2018 Ville Skyttä <ville.skytta@upcloud.com>
# Copyright (c) 2018 Jakub Wilk <jwilk@jwilk.net>

# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/master/COPYING

"""check for signs of poor design"""

from collections import defaultdict
import re

import astroid
from astroid import If, BoolOp
from astroid import decorators

from pylint.interfaces import IAstroidChecker
from pylint.checkers import BaseChecker
from pylint.checkers.utils import check_messages
from pylint import utils


MSGS = {
    "R0901": (
        "Too many ancestors (%s/%s)",
        "too-many-ancestors",
        "Used when class has too many parent classes, try to reduce "
        "this to get a simpler (and so easier to use) class.",
    ),
    "R0902": (
        "Too many instance attributes (%s/%s)",
        "too-many-instance-attributes",
        "Used when class has too many instance attributes, try to reduce "
        "this to get a simpler (and so easier to use) class.",
    ),
    "R0903": (
        "Too few public methods (%s/%s)",
        "too-few-public-methods",
        "Used when class has too few public methods, so be sure it's "
        "really worth it.",
    ),
    "R0904": (
        "Too many public methods (%s/%s)",
        "too-many-public-methods",
        "Used when class has too many public methods, try to reduce "
        "this to get a simpler (and so easier to use) class.",
    ),
    "R0911": (
        "Too many return statements (%s/%s)",
        "too-many-return-statements",
        "Used when a function or method has too many return statement, "
        "making it hard to follow.",
    ),
    "R0912": (
        "Too many branches (%s/%s)",
        "too-many-branches",
        "Used when a function or method has too many branches, "
        "making it hard to follow.",
    ),
    "R0913": (
        "Too many arguments (%s/%s)",
        "too-many-arguments",
        "Used when a function or method takes too many arguments.",
    ),
    "R0914": (
        "Too many local variables (%s/%s)",
        "too-many-locals",
        "Used when a function or method has too many local variables.",
    ),
    "R0915": (
        "Too many statements (%s/%s)",
        "too-many-statements",
        "Used when a function or method has too many statements. You "
        "should then split it in smaller functions / methods.",
    ),
    "R0916": (
        "Too many boolean expressions in if statement (%s/%s)",
        "too-many-boolean-expressions",
        "Used when an if statement contains too many boolean " "expressions.",
    ),
}
SPECIAL_OBJ = re.compile("^_{2}[a-z]+_{2}$")
DATACLASS_DECORATOR = "dataclass"
DATACLASS_IMPORT = "dataclasses"
TYPING_NAMEDTUPLE = "typing.NamedTuple"


def _is_typing_namedtuple(node: astroid.ClassDef) -> bool:
    """Check if a class node is a typing.NamedTuple class"""
    for base in node.ancestors():
        if base.qname() == TYPING_NAMEDTUPLE:
            return True
    return False


def _is_enum_class(node: astroid.ClassDef) -> bool:
    """Check if a class definition defines an Enum class.

    :param node: The class node to check.
    :type node: astroid.ClassDef

    :returns: True if the given node represents an Enum class. False otherwise.
    :rtype: bool
    """
    for base in node.bases:
        try:
            inferred_bases = base.inferred()
        except astroid.InferenceError:
            continue

        for ancestor in inferred_bases:
            if not isinstance(ancestor, astroid.ClassDef):
                continue

            if ancestor.name == "Enum" and ancestor.root().name == "enum":
                return True

    return False


def _is_dataclass(node: astroid.ClassDef) -> bool:
    """Check if a class definition defines a Python 3.7+ dataclass

    :param node: The class node to check.
    :type node: astroid.ClassDef

    :returns: True if the given node represents a dataclass class. False otherwise.
    :rtype: bool
    """
    if not node.decorators:
        return False

    root_locals = node.root().locals
    for decorator in node.decorators.nodes:
        if isinstance(decorator, astroid.Call):
            decorator = decorator.func
        if not isinstance(decorator, (astroid.Name, astroid.Attribute)):
            continue
        if isinstance(decorator, astroid.Name):
            name = decorator.name
        else:
            name = decorator.attrname
        if name == DATACLASS_DECORATOR and DATACLASS_DECORATOR in root_locals:
            return True
    return False


def _count_boolean_expressions(bool_op):
    """Counts the number of boolean expressions in BoolOp `bool_op` (recursive)

    example: a and (b or c or (d and e)) ==> 5 boolean expressions
    """
    nb_bool_expr = 0
    for bool_expr in bool_op.get_children():
        if isinstance(bool_expr, BoolOp):
            nb_bool_expr += _count_boolean_expressions(bool_expr)
        else:
            nb_bool_expr += 1
    return nb_bool_expr


def _count_methods_in_class(node):
    all_methods = sum(1 for method in node.methods() if not method.name.startswith("_"))
    # Special methods count towards the number of public methods,
    # but don't count towards there being too many methods.
    for method in node.mymethods():
        if SPECIAL_OBJ.search(method.name) and method.name != "__init__":
            all_methods += 1
    return all_methods


class MisdesignChecker(BaseChecker):
    """checks for sign of poor/misdesign:
    * number of methods, attributes, local variables...
    * size, complexity of functions, methods
    """

    __implements__ = (IAstroidChecker,)

    # configuration section name
    name = "design"
    # messages
    msgs = MSGS
    priority = -2
    # configuration options
    options = (
        (
            "max-args",
            {
                "default": 5,
                "type": "int",
                "metavar": "<int>",
                "help": "Maximum number of arguments for function / method.",
            },
        ),
        (
            "max-locals",
            {
                "default": 15,
                "type": "int",
                "metavar": "<int>",
                "help": "Maximum number of locals for function / method body.",
            },
        ),
        (
            "max-returns",
            {
                "default": 6,
                "type": "int",
                "metavar": "<int>",
                "help": "Maximum number of return / yield for function / "
                "method body.",
            },
        ),
        (
            "max-branches",
            {
                "default": 12,
                "type": "int",
                "metavar": "<int>",
                "help": "Maximum number of branch for function / method body.",
            },
        ),
        (
            "max-statements",
            {
                "default": 50,
                "type": "int",
                "metavar": "<int>",
                "help": "Maximum number of statements in function / method " "body.",
            },
        ),
        (
            "max-parents",
            {
                "default": 7,
                "type": "int",
                "metavar": "<num>",
                "help": "Maximum number of parents for a class (see R0901).",
            },
        ),
        (
            "max-attributes",
            {
                "default": 7,
                "type": "int",
                "metavar": "<num>",
                "help": "Maximum number of attributes for a class \
(see R0902).",
            },
        ),
        (
            "min-public-methods",
            {
                "default": 2,
                "type": "int",
                "metavar": "<num>",
                "help": "Minimum number of public methods for a class \
(see R0903).",
            },
        ),
        (
            "max-public-methods",
            {
                "default": 20,
                "type": "int",
                "metavar": "<num>",
                "help": "Maximum number of public methods for a class \
(see R0904).",
            },
        ),
        (
            "max-bool-expr",
            {
                "default": 5,
                "type": "int",
                "metavar": "<num>",
                "help": "Maximum number of boolean expressions in an if " "statement.",
            },
        ),
    )

    def __init__(self, linter=None):
        BaseChecker.__init__(self, linter)
        self.stats = None
        self._returns = None
        self._branches = None
        self._stmts = None

    def open(self):
        """initialize visit variables"""
        self.stats = self.linter.add_stats()
        self._returns = []
        self._branches = defaultdict(int)
        self._stmts = []

    def _inc_all_stmts(self, amount):
        for i in range(len(self._stmts)):
            self._stmts[i] += amount

    @decorators.cachedproperty
    def _ignored_argument_names(self):
        return utils.get_global_option(self, "ignored-argument-names", default=None)

    @check_messages(
        "too-many-ancestors",
        "too-many-instance-attributes",
        "too-few-public-methods",
        "too-many-public-methods",
    )
    def visit_classdef(self, node):
        """check size of inheritance hierarchy and number of instance attributes
        """
        nb_parents = len(list(node.ancestors()))
        if nb_parents > self.config.max_parents:
            self.add_message(
                "too-many-ancestors",
                node=node,
                args=(nb_parents, self.config.max_parents),
            )

        if len(node.instance_attrs) > self.config.max_attributes:
            self.add_message(
                "too-many-instance-attributes",
                node=node,
                args=(len(node.instance_attrs), self.config.max_attributes),
            )

    @check_messages("too-few-public-methods", "too-many-public-methods")
    def leave_classdef(self, node):
        """check number of public methods"""
        my_methods = sum(
            1 for method in node.mymethods() if not method.name.startswith("_")
        )

        # Does the class contain less than n public methods ?
        # This checks only the methods defined in the current class,
        # since the user might not have control over the classes
        # from the ancestors. It avoids some false positives
        # for classes such as unittest.TestCase, which provides
        # a lot of assert methods. It doesn't make sense to warn
        # when the user subclasses TestCase to add his own tests.
        if my_methods > self.config.max_public_methods:
            self.add_message(
                "too-many-public-methods",
                node=node,
                args=(my_methods, self.config.max_public_methods),
            )

        # Stop here for exception, metaclass, interface classes and other
        # classes for which we don't need to count the methods.
        if (
            node.type != "class"
            or _is_enum_class(node)
            or _is_dataclass(node)
            or _is_typing_namedtuple(node)
        ):
            return

        # Does the class contain more than n public methods ?
        # This checks all the methods defined by ancestors and
        # by the current class.
        all_methods = _count_methods_in_class(node)
        if all_methods < self.config.min_public_methods:
            self.add_message(
                "too-few-public-methods",
                node=node,
                args=(all_methods, self.config.min_public_methods),
            )

    @check_messages(
        "too-many-return-statements",
        "too-many-branches",
        "too-many-arguments",
        "too-many-locals",
        "too-many-statements",
        "keyword-arg-before-vararg",
    )
    def visit_functiondef(self, node):
        """check function name, docstring, arguments, redefinition,
        variable names, max locals
        """
        # init branch and returns counters
        self._returns.append(0)
        # check number of arguments
        args = node.args.args
        ignored_argument_names = self._ignored_argument_names
        if args is not None:
            ignored_args_num = 0
            if ignored_argument_names:
                ignored_args_num = sum(
                    1 for arg in args if ignored_argument_names.match(arg.name)
                )

            argnum = len(args) - ignored_args_num
            if argnum > self.config.max_args:
                self.add_message(
                    "too-many-arguments",
                    node=node,
                    args=(len(args), self.config.max_args),
                )
        else:
            ignored_args_num = 0
        # check number of local variables
        locnum = len(node.locals) - ignored_args_num
        if locnum > self.config.max_locals:
            self.add_message(
                "too-many-locals", node=node, args=(locnum, self.config.max_locals)
            )
        # init new statements counter
        self._stmts.append(1)

    visit_asyncfunctiondef = visit_functiondef

    @check_messages(
        "too-many-return-statements",
        "too-many-branches",
        "too-many-arguments",
        "too-many-locals",
        "too-many-statements",
    )
    def leave_functiondef(self, node):
        """most of the work is done here on close:
        checks for max returns, branch, return in __init__
        """
        returns = self._returns.pop()
        if returns > self.config.max_returns:
            self.add_message(
                "too-many-return-statements",
                node=node,
                args=(returns, self.config.max_returns),
            )
        branches = self._branches[node]
        if branches > self.config.max_branches:
            self.add_message(
                "too-many-branches",
                node=node,
                args=(branches, self.config.max_branches),
            )
        # check number of statements
        stmts = self._stmts.pop()
        if stmts > self.config.max_statements:
            self.add_message(
                "too-many-statements",
                node=node,
                args=(stmts, self.config.max_statements),
            )

    leave_asyncfunctiondef = leave_functiondef

    def visit_return(self, _):
        """count number of returns"""
        if not self._returns:
            return  # return outside function, reported by the base checker
        self._returns[-1] += 1

    def visit_default(self, node):
        """default visit method -> increments the statements counter if
        necessary
        """
        if node.is_statement:
            self._inc_all_stmts(1)

    def visit_tryexcept(self, node):
        """increments the branches counter"""
        branches = len(node.handlers)
        if node.orelse:
            branches += 1
        self._inc_branch(node, branches)
        self._inc_all_stmts(branches)

    def visit_tryfinally(self, node):
        """increments the branches counter"""
        self._inc_branch(node, 2)
        self._inc_all_stmts(2)

    @check_messages("too-many-boolean-expressions")
    def visit_if(self, node):
        """increments the branches counter and checks boolean expressions"""
        self._check_boolean_expressions(node)
        branches = 1
        # don't double count If nodes coming from some 'elif'
        if node.orelse and (len(node.orelse) > 1 or not isinstance(node.orelse[0], If)):
            branches += 1
        self._inc_branch(node, branches)
        self._inc_all_stmts(branches)

    def _check_boolean_expressions(self, node):
        """Go through "if" node `node` and counts its boolean expressions

        if the "if" node test is a BoolOp node
        """
        condition = node.test
        if not isinstance(condition, BoolOp):
            return
        nb_bool_expr = _count_boolean_expressions(condition)
        if nb_bool_expr > self.config.max_bool_expr:
            self.add_message(
                "too-many-boolean-expressions",
                node=condition,
                args=(nb_bool_expr, self.config.max_bool_expr),
            )

    def visit_while(self, node):
        """increments the branches counter"""
        branches = 1
        if node.orelse:
            branches += 1
        self._inc_branch(node, branches)

    visit_for = visit_while

    def _inc_branch(self, node, branchesnum=1):
        """increments the branches counter"""
        self._branches[node.scope()] += branchesnum


def register(linter):
    """required method to auto register this checker """
    linter.register_checker(MisdesignChecker(linter))