yorm.get_mapper() - Code Metrics - Inspection of "Monkey patch methods rather than modify the class" - jacebrowning/yorm - Measure and Improve Code Quality continuously with Scrutinizer

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Push — develop ( 177319...6ce2f8 )

by Jace

created 2016-02-11 04:13 UTC

yorm.get_mapper() B

↳ Parent: Project

Complexity

Conditions

Size

Total Lines

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	9
CRAP Score	5

Metric	Value
cc	5
dl	0
loc	12
ccs	9
cts	9
cp	1
crap	5
rs	8.5454

"""Core YAML mapping functionality."""

import os
import abc
import functools
from pprint import pformat

from . import common, exceptions, settings
from .bases import Container

MAPPER = '__mapper__'

log = common.logger(__name__)


def get_mapper(obj, allow_missing=False):
    """Get `Mapper` instance attached to an object."""
    try:
        mapper = getattr(obj, MAPPER)
    except AttributeError:
        if allow_missing or isinstance(obj, (dict, list)):
            mapper = None
        else:
            msg = "Mapped {!r} missing {!r} attribute".format(obj, MAPPER)
            raise AttributeError(msg) from None
    else:
        return mapper


def set_mapper(obj, path, attrs, auto=True, root=None):
    """Create and attach a `Mapper` instance to an object."""
    mapper = Mapper(obj, path, attrs, auto=auto, root=root)
    setattr(obj, MAPPER, mapper)
    return mapper


def file_required(create=False):
    """Decorator for methods that require the file to exist.

    :param create: boolean or the method to decorate

    """
    def decorator(method):

        @functools.wraps(method)
        def wrapped(self, *args, **kwargs):  # pylint: disable=W0621
            if not self.path:
                return None
            if not self.exists and self.auto:
                if create is True and not self.deleted:
                    self.create()
                else:
                    msg = "cannot access deleted: {}".format(self.path)
                    raise exceptions.FileDeletedError(msg)
            return method(self, *args, **kwargs)

        return wrapped

    if callable(create):
        return decorator(create)
    else:
        return decorator


def prevent_recursion(method):
    """Decorator to prevent indirect recursive calls."""

    @functools.wraps(method)
    def wrapped(self, *args, **kwargs):
        # pylint: disable=W0212
        if self._activity:
            return
        self._activity = True
        result = method(self, *args, **kwargs)
        self._activity = False
        return result

    return wrapped


def prefix(obj):
    """Prefix a string with a fake designator if enabled."""
    fake = "(fake) " if settings.fake else ""
    name = obj if isinstance(obj, str) else "'{}'".format(obj)
    return fake + name


class BaseHelper(metaclass=abc.ABCMeta):
    """Utility class to map attributes to text files.

    To start mapping attributes to a file:

        create -> [empty] -> FILE

    When getting an attribute:

        FILE -> read -> [text] -> load -> [dict] -> fetch -> ATTRIBUTES

    When setting an attribute:

        ATTRIBUTES -> store -> [dict] -> dump -> [text] -> write -> FILE

    After the mapped file is no longer needed:

        delete -> [null] -> FILE

    """

    def __init__(self, path, auto=True):
        self.path = path
        self.auto = auto
        self.auto_store = False
        self.exists = self.path and os.path.isfile(self.path)
        self.deleted = False
        self._activity = False
        self._timestamp = 0
        self._fake = ""

    def __str__(self):
        return str(self.path)

    @property
    def text(self):
        """Get file contents."""
        log.info("Getting contents of %s...", prefix(self))
        if settings.fake:
            text = self._fake
        else:
            text = self._read()
        log.trace("Text read: \n%s", text[:-1])
        return text

    @text.setter
    def text(self, text):
        """Set file contents."""
        log.info("Setting contents of %s...", prefix(self))
        if settings.fake:
            self._fake = text
        else:
            self._write(text)
        log.trace("Text wrote: \n%s", text[:-1])
        self.modified = True

    @property
    def modified(self):
        """Determine if the file has been modified."""
        if settings.fake:
            changes = self._timestamp is not None
            return changes
        elif not self.exists:
            return True
        else:
            was = self._timestamp
            now = common.stamp(self.path)
            return was != now

    @modified.setter
    def modified(self, changes):
        """Mark the file as modified if there are changes."""
        if changes:
            log.debug("Marked %s as modified", prefix(self))
            self._timestamp = 0
        else:
            if settings.fake or self.path is None:
                self._timestamp = None
            else:
                self._timestamp = common.stamp(self.path)
            log.debug("Marked %s as unmodified", prefix(self))

    @property
    def ext(self):
        if '.' in self.path:
            return self.path.split('.')[-1]
        else:
            return 'yml'

    def create(self, obj):
        """Create a new file for the object."""
        log.info("Creating %s for %r...", prefix(self), obj)
        if self.exists:
            log.warning("Already created: %s", self)
            return
        if not settings.fake:
            common.create_dirname(self.path)
            common.touch(self.path)
        self.exists = True
        self.deleted = False

    @file_required
    @prevent_recursion
    def fetch(self, obj, attrs):
        """Update the object's mapped attributes from its file."""
        log.info("Fetching %r from %s...", obj, prefix(self))

        # Parse data from file
        text = self._read()
        data = self._load(text=text, path=self.path, ext=self.ext)
        log.trace("Loaded data: \n%s", pformat(data))

        # Update all attributes
        attrs2 = attrs.copy()
        for name, data in data.items():
            attrs2.pop(name, None)

            # Find a matching converter
            try:
                converter = attrs[name]
            except KeyError:
                # TODO: determine if runtime import is the best way to avoid
                # cyclic import
                from .converters import match
                converter = match(name, data)
                attrs[name] = converter

            # Convert the loaded attribute
            attr = getattr(obj, name, None)
            if all((isinstance(attr, converter),
                    issubclass(converter, Container))):
                attr.update_value(data)
            else:
                attr = converter.to_value(data)
                setattr(obj, name, attr)
            self._remap(attr)
            log.trace("Value fetched: %s = %r", name, attr)

        # Add missing attributes
        for name, converter in attrs2.items():
            if not hasattr(obj, name):
                value = converter.to_value(None)
                msg = "Fetched default value for missing attribute: %s = %r"
                log.warning(msg, name, value)
                setattr(obj, name, value)

        # Set meta attributes
        self.modified = False

    @file_required(create=True)
    @prevent_recursion
    def store(self, obj, attrs):
        """Format and save the object's mapped attributes to its file."""
        log.info("Storing %r to %s...", obj, prefix(self))

        # Format the data items
        data = {}
        for name, converter in attrs.items():
            try:
                value = getattr(obj, name)
            except AttributeError:
                value = None
                msg = "Storing default data for missing attribute '%s'..."
                log.warning(msg, name)

            data2 = converter.to_data(value)

            log.trace("Data to store: %s = %r", name, data2)
            data[name] = data2

        # Dump data to file
        text = self._dump(data=data, ext=self.ext)
        self._write(text)

        # Set meta attributes
        self.modified = True
        self.auto_store = self.auto

    def delete(self):
        """Delete the object's file from the file system."""
        if self.exists:
            log.info("Deleting %s...", prefix(self))
            if not settings.fake:
                common.delete(self.path)
        else:
            log.warning("Already deleted: %s", self)
        self.exists = False
        self.deleted = True

    @file_required
    def _read(self):
        """Read text from the object's file.

        :param path: path to a text file

        :return: contexts of text file

        """
        if settings.fake:
            return self._fake
        elif not self.exists:
            return ""
        else:
            return common.read_text(self.path)

    @file_required
    def _write(self, text):
        """Write text to the object's file.

        :param text: text to write to a file
        :param path: path to the file

        """
        if settings.fake:
            self._fake = text
        else:
            common.write_text(text, self.path)

    @abc.abstractstaticmethod
    def _load(text, path, ext):  # pragma: no cover (abstract method)
        """Parsed data from text.

        :param text: text read from a file
        :param path: path to the file (for displaying errors)

        :return: dictionary of parsed data

        """
        raise NotImplementedError

    @abc.abstractstaticmethod
    def _dump(data, ext):  # pragma: no cover (abstract method)
        """Dump data to text.

        :param data: dictionary of data

        :return: text to write to a file

        """
        raise NotImplementedError

    def _remap(self, obj):
        """Restore mapping on nested attributes."""
        if isinstance(obj, Container):
            set_mapper(obj, None, common.attrs[obj.__class__], root=self)
            if isinstance(obj, dict):
                for obj2 in obj.values():
                    self._remap(obj2)
            else:
                assert isinstance(obj, list)
                for obj2 in obj:
                    self._remap(obj2)


class Helper(BaseHelper):
    """Utility class to map attributes to YAML files."""

    @staticmethod
    def _load(text, path, ext):
        """Load YAML data from text.

        :param text: text read from a file
        :param path: path to the file (for displaying errors)

        :return: dictionary of YAML data

        """
        return common.load_file(text, path, ext)

    @staticmethod
    def _dump(data, ext):
        """Dump YAML data to text.

        :param data: dictionary of YAML data

        :return: text to write to a file

        """
        return common.dump_file(data, ext)


class Mapper(Helper):
    """Maps an object's attribute to YAML files."""

    def __init__(self, obj, path, attrs, auto=True, root=None):
        super().__init__(path, auto=auto)
        self.obj = obj
        self.attrs = attrs
        self.root = root

    def create(self):  # pylint: disable=W0221
        super().create(self.obj)

    def fetch(self):  # pylint: disable=W0221
        if self.root and self.root.auto and not self._activity:
            self._activity = True
            self.root.fetch()
            self._activity = False
        super().fetch(self.obj, self.attrs)

    def store(self):  # pylint: disable=W0221
        if self.root and self.root.auto and not self._activity:
            self._activity = True
            self.root.store()
            self._activity = False
        super().store(self.obj, self.attrs)


1		"""Core YAML mapping functionality."""
2
3	1	import os
4	1	import abc
5	1	import functools
6	1	from pprint import pformat
7
8	1	from . import common, exceptions, settings
9	1	from .bases import Container
10
11	1	MAPPER = '__mapper__'
12
13	1	log = common.logger(__name__)
14
15
16	1	def get_mapper(obj, allow_missing=False):
17		"""Get `Mapper` instance attached to an object."""
18	1	try:
19	1	mapper = getattr(obj, MAPPER)
20	1	except AttributeError:
21	1	if allow_missing or isinstance(obj, (dict, list)):
22	1	mapper = None
23		else:
24	1	msg = "Mapped {!r} missing {!r} attribute".format(obj, MAPPER)
25	1	raise AttributeError(msg) from None
26		else:
27	1	return mapper
28
29
30	1	def set_mapper(obj, path, attrs, auto=True, root=None):
31		"""Create and attach a `Mapper` instance to an object."""
32	1	mapper = Mapper(obj, path, attrs, auto=auto, root=root)
33	1	setattr(obj, MAPPER, mapper)
34	1	return mapper
35
36
37	1	def file_required(create=False):
38		"""Decorator for methods that require the file to exist.
39
40		:param create: boolean or the method to decorate
41
42		"""
43	1	def decorator(method):
44
45	1	@functools.wraps(method)
46		def wrapped(self, args, *kwargs): # pylint: disable=W0621
47	1	if not self.path:
48	1	return None
49	1	if not self.exists and self.auto:
50	1	if create is True and not self.deleted:
51	1	self.create()
52		else:
53	1	msg = "cannot access deleted: {}".format(self.path)
54	1	raise exceptions.FileDeletedError(msg)
55	1	return method(self, args, *kwargs)
56
57	1	return wrapped
58
59	1	if callable(create):
60	1	return decorator(create)
61		else:
62	1	return decorator
63
64
65	1	def prevent_recursion(method):
66		"""Decorator to prevent indirect recursive calls."""
67
68	1	@functools.wraps(method)
69		def wrapped(self, args, *kwargs):
70		# pylint: disable=W0212
71	1	if self._activity:
72	1	return
73	1	self._activity = True
74	1	result = method(self, args, *kwargs)
75	1	self._activity = False
76	1	return result
77
78	1	return wrapped
79
80
81	1	def prefix(obj):
82		"""Prefix a string with a fake designator if enabled."""
83	1	fake = "(fake) " if settings.fake else ""
84	1	name = obj if isinstance(obj, str) else "'{}'".format(obj)
85	1	return fake + name
86
87
88	1	class BaseHelper(metaclass=abc.ABCMeta):
89		"""Utility class to map attributes to text files.
90
91		To start mapping attributes to a file:
92
93		create -> [empty] -> FILE
94
95		When getting an attribute:
96
97		FILE -> read -> [text] -> load -> [dict] -> fetch -> ATTRIBUTES
98
99		When setting an attribute:
100
101		ATTRIBUTES -> store -> [dict] -> dump -> [text] -> write -> FILE
102
103		After the mapped file is no longer needed:
104
105		delete -> [null] -> FILE
106
107		"""
108
109	1	def __init__(self, path, auto=True):
110	1	self.path = path
111	1	self.auto = auto
112	1	self.auto_store = False
113	1	self.exists = self.path and os.path.isfile(self.path)
114	1	self.deleted = False
115	1	self._activity = False
116	1	self._timestamp = 0
117	1	self._fake = ""
118
119	1	def __str__(self):
120	1	return str(self.path)
121
122	1	@property
123		def text(self):
124		"""Get file contents."""
125	1	log.info("Getting contents of %s...", prefix(self))
126	1	if settings.fake:
127	1	text = self._fake
128		else:
129	1	text = self._read()
130	1	log.trace("Text read: \n%s", text[:-1])
131	1	return text
132
133	1	@text.setter
134		def text(self, text):
135		"""Set file contents."""
136	1	log.info("Setting contents of %s...", prefix(self))
137	1	if settings.fake:
138	1	self._fake = text
139		else:
140	1	self._write(text)
141	1	log.trace("Text wrote: \n%s", text[:-1])
142	1	self.modified = True
143
144	1	@property
145		def modified(self):
146		"""Determine if the file has been modified."""
147	1	if settings.fake:
148	1	changes = self._timestamp is not None
149	1	return changes
150	1	elif not self.exists:
151	1	return True
152		else:
153	1	was = self._timestamp
154	1	now = common.stamp(self.path)
155	1	return was != now
156
157	1	@modified.setter
158		def modified(self, changes):
159		"""Mark the file as modified if there are changes."""
160	1	if changes:
161	1	log.debug("Marked %s as modified", prefix(self))
162	1	self._timestamp = 0
163		else:
164	1	if settings.fake or self.path is None:
165	1	self._timestamp = None
166		else:
167	1	self._timestamp = common.stamp(self.path)
168	1	log.debug("Marked %s as unmodified", prefix(self))
169
170	1	@property
171		def ext(self):
172	1	if '.' in self.path:
173	1	return self.path.split('.')[-1]
174		else:
175	1	return 'yml'
176
177	1	def create(self, obj):
178		"""Create a new file for the object."""
179	1	log.info("Creating %s for %r...", prefix(self), obj)
180	1	if self.exists:
181	1	log.warning("Already created: %s", self)
182	1	return
183	1	if not settings.fake:
184	1	common.create_dirname(self.path)
185	1	common.touch(self.path)
186	1	self.exists = True
187	1	self.deleted = False
188
189	1	@file_required
190	1	@prevent_recursion
191		def fetch(self, obj, attrs):
192		"""Update the object's mapped attributes from its file."""
193	1	log.info("Fetching %r from %s...", obj, prefix(self))
194
195		# Parse data from file
196	1	text = self._read()
197	1	data = self._load(text=text, path=self.path, ext=self.ext)
198	1	log.trace("Loaded data: \n%s", pformat(data))
199
200		# Update all attributes
201	1	attrs2 = attrs.copy()
202	1	for name, data in data.items():
203	1	attrs2.pop(name, None)
204
205		# Find a matching converter
206	1	try:
207	1	converter = attrs[name]
208	1	except KeyError:
209		# TODO: determine if runtime import is the best way to avoid
210		# cyclic import
211	1	from .converters import match
212	1	converter = match(name, data)
213	1	attrs[name] = converter
214
215		# Convert the loaded attribute
216	1	attr = getattr(obj, name, None)
217	1	if all((isinstance(attr, converter),
218		issubclass(converter, Container))):
219	1	attr.update_value(data)
220		else:
221	1	attr = converter.to_value(data)
222	1	setattr(obj, name, attr)
223	1	self._remap(attr)
224	1	log.trace("Value fetched: %s = %r", name, attr)
225
226		# Add missing attributes
227	1	for name, converter in attrs2.items():
228	1	if not hasattr(obj, name):
229	1	value = converter.to_value(None)
230	1	msg = "Fetched default value for missing attribute: %s = %r"
231	1	log.warning(msg, name, value)
232	1	setattr(obj, name, value)
233
234		# Set meta attributes
235	1	self.modified = False
236
237	1	@file_required(create=True)
238	1	@prevent_recursion
239		def store(self, obj, attrs):
240		"""Format and save the object's mapped attributes to its file."""
241	1	log.info("Storing %r to %s...", obj, prefix(self))
242
243		# Format the data items
244	1	data = {}
245	1	for name, converter in attrs.items():
246	1	try:
247	1	value = getattr(obj, name)
248	1	except AttributeError:
249	1	value = None
250	1	msg = "Storing default data for missing attribute '%s'..."
251	1	log.warning(msg, name)
252
253	1	data2 = converter.to_data(value)
254
255	1	log.trace("Data to store: %s = %r", name, data2)
256	1	data[name] = data2
257
258		# Dump data to file
259	1	text = self._dump(data=data, ext=self.ext)
260	1	self._write(text)
261
262		# Set meta attributes
263	1	self.modified = True
264	1	self.auto_store = self.auto
265
266	1	def delete(self):
267		"""Delete the object's file from the file system."""
268	1	if self.exists:
269	1	log.info("Deleting %s...", prefix(self))
270	1	if not settings.fake:
271	1	common.delete(self.path)
272		else:
273	1	log.warning("Already deleted: %s", self)
274	1	self.exists = False
275	1	self.deleted = True
276
277	1	@file_required
278		def _read(self):
279		"""Read text from the object's file.
280
281		:param path: path to a text file
282
283		:return: contexts of text file
284
285		"""
286	1	if settings.fake:
287	1	return self._fake
288	1	elif not self.exists:
289	1	return ""
290		else:
291	1	return common.read_text(self.path)
292
293	1	@file_required
294		def _write(self, text):
295		"""Write text to the object's file.
296
297		:param text: text to write to a file
298		:param path: path to the file
299
300		"""
301	1	if settings.fake:
302	1	self._fake = text
303		else:
304	1	common.write_text(text, self.path)
305
306	1	@abc.abstractstaticmethod
307		def _load(text, path, ext): # pragma: no cover (abstract method)
308		"""Parsed data from text.
309
310		:param text: text read from a file
311		:param path: path to the file (for displaying errors)
312
313		:return: dictionary of parsed data
314
315		"""
316		raise NotImplementedError
317
318	1	@abc.abstractstaticmethod
319		def _dump(data, ext): # pragma: no cover (abstract method)
320		"""Dump data to text.
321
322		:param data: dictionary of data
323
324		:return: text to write to a file
325
326		"""
327		raise NotImplementedError
328
329	1	def _remap(self, obj):
330		"""Restore mapping on nested attributes."""
331	1	if isinstance(obj, Container):
332	1	set_mapper(obj, None, common.attrs[obj.__class__], root=self)
333	1	if isinstance(obj, dict):
334	1	for obj2 in obj.values():
335	1	self._remap(obj2)
336		else:
337	1	assert isinstance(obj, list)
338	1	for obj2 in obj:
339	1	self._remap(obj2)
340
341
342	1	class Helper(BaseHelper):
343		"""Utility class to map attributes to YAML files."""
344
345	1	@staticmethod
346		def _load(text, path, ext):
347		"""Load YAML data from text.
348
349		:param text: text read from a file
350		:param path: path to the file (for displaying errors)
351
352		:return: dictionary of YAML data
353
354		"""
355	1	return common.load_file(text, path, ext)
356
357	1	@staticmethod
358		def _dump(data, ext):
359		"""Dump YAML data to text.
360
361		:param data: dictionary of YAML data
362
363		:return: text to write to a file
364
365		"""
366	1	return common.dump_file(data, ext)
367
368
369	1	class Mapper(Helper):
370		"""Maps an object's attribute to YAML files."""
371
372	1	def __init__(self, obj, path, attrs, auto=True, root=None):
373	1	super().__init__(path, auto=auto)
374	1	self.obj = obj
375	1	self.attrs = attrs
376	1	self.root = root
377
378	1	def create(self): # pylint: disable=W0221
379	1	super().create(self.obj)
380
381	1	def fetch(self): # pylint: disable=W0221
382	1	if self.root and self.root.auto and not self._activity:
383	1	self._activity = True
384	1	self.root.fetch()
385	1	self._activity = False
386	1	super().fetch(self.obj, self.attrs)
387
388	1	def store(self): # pylint: disable=W0221
389	1	if self.root and self.root.auto and not self._activity:
390	1	self._activity = True
391	1	self.root.store()
392	1	self._activity = False
393		super().store(self.obj, self.attrs)
394

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