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Commit01d9150

Browse files
authored
GH-128520: Makepathlib._abc.WritablePath a sibling ofReadablePath (#129014)
In the private pathlib ABCs, support write-only virtual filesystems bymaking `WritablePath` inherit directly from `JoinablePath`, rather thansubclassing `ReadablePath`.There are two complications:- `ReadablePath.open()` applies to both reading and writing- `ReadablePath.copy` is secretly an object that supports the *read* side of copying, whereas `WritablePath.copy` is a different kind of object supporting the *write* sideWe untangle these as follow:- A new `pathlib._abc.magic_open()` function replaces the `open()` method, which is dropped from the ABCs but remains in `pathlib.Path`. The function works like `io.open()`, but additionally accepts objects with `__open_rb__()` or `__open_wb__()` methods as appropriate for the mode. These new dunders are made abstract methods of `ReadablePath` and `WritablePath` respectively. If the pathlib ABCs are made public, we could consider blessing an "openable" protocol and supporting it in `io.open()`, removing the need for `pathlib._abc.magic_open()`.- `ReadablePath.copy` becomes a true method, whereas `WritablePath.copy` is deleted. A new `ReadablePath._copy_reader` property provides a `CopyReader` object, and similarly `WritablePath._copy_writer` is a `CopyWriter` object. OnceGH-125413 is resolved, we'll be able to move the `CopyReader` functionality into `ReadablePath.info` and eliminate `ReadablePath._copy_reader`.
1 parent3d7c0e5 commit01d9150

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4 files changed

+178
-115
lines changed

4 files changed

+178
-115
lines changed

‎Lib/pathlib/_abc.py

Lines changed: 90 additions & 46 deletions
Original file line numberDiff line numberDiff line change
@@ -12,6 +12,7 @@
1212
"""
1313

1414
importfunctools
15+
importio
1516
importoperator
1617
importposixpath
1718
fromerrnoimportEINVAL
@@ -41,6 +42,40 @@ def _explode_path(path):
4142
returnpath,names
4243

4344

45+
defmagic_open(path,mode='r',buffering=-1,encoding=None,errors=None,
46+
newline=None):
47+
"""
48+
Open the file pointed to by this path and return a file object, as
49+
the built-in open() function does.
50+
"""
51+
try:
52+
returnio.open(path,mode,buffering,encoding,errors,newline)
53+
exceptTypeError:
54+
pass
55+
cls=type(path)
56+
text='b'notinmode
57+
mode=''.join(sorted(cforcinmodeifcnotin'bt'))
58+
iftext:
59+
try:
60+
attr=getattr(cls,f'__open_{mode}__')
61+
exceptAttributeError:
62+
pass
63+
else:
64+
returnattr(path,buffering,encoding,errors,newline)
65+
66+
try:
67+
attr=getattr(cls,f'__open_{mode}b__')
68+
exceptAttributeError:
69+
pass
70+
else:
71+
stream=attr(path,buffering)
72+
iftext:
73+
stream=io.TextIOWrapper(stream,encoding,errors,newline)
74+
returnstream
75+
76+
raiseTypeError(f"{cls.__name__} can't be opened with mode{mode!r}")
77+
78+
4479
classPathGlobber(_GlobberBase):
4580
"""
4681
Class providing shell-style globbing for path objects.
@@ -58,35 +93,15 @@ def concat_path(path, text):
5893

5994
classCopyReader:
6095
"""
61-
Class that implements copying between path objects. An instance of this
62-
class is available from the ReadablePath.copy property; it's made callable
63-
so that ReadablePath.copy() can be treated as a method.
64-
65-
The target path's CopyWriter drives the process from its _create() method.
66-
Files and directories are exchanged by calling methods on the source and
67-
target paths, and metadata is exchanged by calling
68-
source.copy._read_metadata() and target.copy._write_metadata().
96+
Class that implements the "read" part of copying between path objects.
97+
An instance of this class is available from the ReadablePath._copy_reader
98+
property.
6999
"""
70100
__slots__= ('_path',)
71101

72102
def__init__(self,path):
73103
self._path=path
74104

75-
def__call__(self,target,follow_symlinks=True,dirs_exist_ok=False,
76-
preserve_metadata=False):
77-
"""
78-
Recursively copy this file or directory tree to the given destination.
79-
"""
80-
ifnotisinstance(target,ReadablePath):
81-
target=self._path.with_segments(target)
82-
83-
# Delegate to the target path's CopyWriter object.
84-
try:
85-
create=target.copy._create
86-
exceptAttributeError:
87-
raiseTypeError(f"Target is not writable:{target}")fromNone
88-
returncreate(self._path,follow_symlinks,dirs_exist_ok,preserve_metadata)
89-
90105
_readable_metakeys=frozenset()
91106

92107
def_read_metadata(self,metakeys,*,follow_symlinks=True):
@@ -96,8 +111,16 @@ def _read_metadata(self, metakeys, *, follow_symlinks=True):
96111
raiseNotImplementedError
97112

98113

99-
classCopyWriter(CopyReader):
100-
__slots__= ()
114+
classCopyWriter:
115+
"""
116+
Class that implements the "write" part of copying between path objects. An
117+
instance of this class is available from the WritablePath._copy_writer
118+
property.
119+
"""
120+
__slots__= ('_path',)
121+
122+
def__init__(self,path):
123+
self._path=path
101124

102125
_writable_metakeys=frozenset()
103126

@@ -110,7 +133,7 @@ def _write_metadata(self, metadata, *, follow_symlinks=True):
110133
def_create(self,source,follow_symlinks,dirs_exist_ok,preserve_metadata):
111134
self._ensure_distinct_path(source)
112135
ifpreserve_metadata:
113-
metakeys=self._writable_metakeys&source.copy._readable_metakeys
136+
metakeys=self._writable_metakeys&source._copy_reader._readable_metakeys
114137
else:
115138
metakeys=None
116139
ifnotfollow_symlinksandsource.is_symlink():
@@ -128,22 +151,22 @@ def _create_dir(self, source, metakeys, follow_symlinks, dirs_exist_ok):
128151
forsrcinchildren:
129152
dst=self._path.joinpath(src.name)
130153
ifnotfollow_symlinksandsrc.is_symlink():
131-
dst.copy._create_symlink(src,metakeys)
154+
dst._copy_writer._create_symlink(src,metakeys)
132155
elifsrc.is_dir():
133-
dst.copy._create_dir(src,metakeys,follow_symlinks,dirs_exist_ok)
156+
dst._copy_writer._create_dir(src,metakeys,follow_symlinks,dirs_exist_ok)
134157
else:
135-
dst.copy._create_file(src,metakeys)
158+
dst._copy_writer._create_file(src,metakeys)
136159
ifmetakeys:
137-
metadata=source.copy._read_metadata(metakeys)
160+
metadata=source._copy_reader._read_metadata(metakeys)
138161
ifmetadata:
139162
self._write_metadata(metadata)
140163

141164
def_create_file(self,source,metakeys):
142165
"""Copy the given file to our path."""
143166
self._ensure_different_file(source)
144-
withsource.open('rb')assource_f:
167+
withmagic_open(source,'rb')assource_f:
145168
try:
146-
withself._path.open('wb')astarget_f:
169+
withmagic_open(self._path,'wb')astarget_f:
147170
copyfileobj(source_f,target_f)
148171
exceptIsADirectoryErrorase:
149172
ifnotself._path.exists():
@@ -152,15 +175,15 @@ def _create_file(self, source, metakeys):
152175
f'Directory does not exist:{self._path}')frome
153176
raise
154177
ifmetakeys:
155-
metadata=source.copy._read_metadata(metakeys)
178+
metadata=source._copy_reader._read_metadata(metakeys)
156179
ifmetadata:
157180
self._write_metadata(metadata)
158181

159182
def_create_symlink(self,source,metakeys):
160183
"""Copy the given symbolic link to our path."""
161184
self._path.symlink_to(source.readlink())
162185
ifmetakeys:
163-
metadata=source.copy._read_metadata(metakeys,follow_symlinks=False)
186+
metadata=source._copy_reader._read_metadata(metakeys,follow_symlinks=False)
164187
ifmetadata:
165188
self._write_metadata(metadata,follow_symlinks=False)
166189

@@ -420,26 +443,25 @@ def is_symlink(self):
420443
"""
421444
raiseNotImplementedError
422445

423-
defopen(self,mode='r',buffering=-1,encoding=None,
424-
errors=None,newline=None):
446+
def__open_rb__(self,buffering=-1):
425447
"""
426-
Open the file pointed to by this pathand return a file object, as
427-
the built-inopen() function does.
448+
Open the file pointed to by this pathfor reading in binary mode and
449+
return a file object, likeopen(mode='rb').
428450
"""
429451
raiseNotImplementedError
430452

431453
defread_bytes(self):
432454
"""
433455
Open the file in bytes mode, read it, and close the file.
434456
"""
435-
withself.open(mode='rb',buffering=0)asf:
457+
withmagic_open(self,mode='rb',buffering=0)asf:
436458
returnf.read()
437459

438460
defread_text(self,encoding=None,errors=None,newline=None):
439461
"""
440462
Open the file in text mode, read it, and close the file.
441463
"""
442-
withself.open(mode='r',encoding=encoding,errors=errors,newline=newline)asf:
464+
withmagic_open(self,mode='r',encoding=encoding,errors=errors,newline=newline)asf:
443465
returnf.read()
444466

445467
def_scandir(self):
@@ -532,7 +554,22 @@ def readlink(self):
532554
"""
533555
raiseNotImplementedError
534556

535-
copy=property(CopyReader,doc=CopyReader.__call__.__doc__)
557+
_copy_reader=property(CopyReader)
558+
559+
defcopy(self,target,follow_symlinks=True,dirs_exist_ok=False,
560+
preserve_metadata=False):
561+
"""
562+
Recursively copy this file or directory tree to the given destination.
563+
"""
564+
ifnothasattr(target,'_copy_writer'):
565+
target=self.with_segments(target)
566+
567+
# Delegate to the target path's CopyWriter object.
568+
try:
569+
create=target._copy_writer._create
570+
exceptAttributeError:
571+
raiseTypeError(f"Target is not writable:{target}")fromNone
572+
returncreate(self,follow_symlinks,dirs_exist_ok,preserve_metadata)
536573

537574
defcopy_into(self,target_dir,*,follow_symlinks=True,
538575
dirs_exist_ok=False,preserve_metadata=False):
@@ -542,7 +579,7 @@ def copy_into(self, target_dir, *, follow_symlinks=True,
542579
name=self.name
543580
ifnotname:
544581
raiseValueError(f"{self!r} has an empty name")
545-
elifisinstance(target_dir,ReadablePath):
582+
elifhasattr(target_dir,'_copy_writer'):
546583
target=target_dir/name
547584
else:
548585
target=self.with_segments(target_dir,name)
@@ -551,7 +588,7 @@ def copy_into(self, target_dir, *, follow_symlinks=True,
551588
preserve_metadata=preserve_metadata)
552589

553590

554-
classWritablePath(ReadablePath):
591+
classWritablePath(JoinablePath):
555592
__slots__= ()
556593

557594
defsymlink_to(self,target,target_is_directory=False):
@@ -567,13 +604,20 @@ def mkdir(self, mode=0o777, parents=False, exist_ok=False):
567604
"""
568605
raiseNotImplementedError
569606

607+
def__open_wb__(self,buffering=-1):
608+
"""
609+
Open the file pointed to by this path for writing in binary mode and
610+
return a file object, like open(mode='wb').
611+
"""
612+
raiseNotImplementedError
613+
570614
defwrite_bytes(self,data):
571615
"""
572616
Open the file in bytes mode, write to it, and close the file.
573617
"""
574618
# type-check for the buffer interface before truncating the file
575619
view=memoryview(data)
576-
withself.open(mode='wb')asf:
620+
withmagic_open(self,mode='wb')asf:
577621
returnf.write(view)
578622

579623
defwrite_text(self,data,encoding=None,errors=None,newline=None):
@@ -583,7 +627,7 @@ def write_text(self, data, encoding=None, errors=None, newline=None):
583627
ifnotisinstance(data,str):
584628
raiseTypeError('data must be str, not %s'%
585629
data.__class__.__name__)
586-
withself.open(mode='w',encoding=encoding,errors=errors,newline=newline)asf:
630+
withmagic_open(self,mode='w',encoding=encoding,errors=errors,newline=newline)asf:
587631
returnf.write(data)
588632

589-
copy=property(CopyWriter,doc=CopyWriter.__call__.__doc__)
633+
_copy_writer=property(CopyWriter)

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