forked from localstack/localstack
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathpatch.py
More file actions
260 lines (198 loc) · 7.85 KB
/
patch.py
File metadata and controls
260 lines (198 loc) · 7.85 KB
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
import functools
import inspect
import types
from collections.abc import Callable
from typing import Any
def get_defining_object(method):
"""Returns either the class or the module that defines the given function/method."""
# adapted from https://stackoverflow.com/a/25959545/804840
if inspect.ismethod(method):
return method.__self__
if inspect.isfunction(method):
class_name = method.__qualname__.split(".<locals>", 1)[0].rsplit(".", 1)[0]
try:
# method is not bound but referenced by a class, like MyClass.mymethod
cls = getattr(inspect.getmodule(method), class_name)
except AttributeError:
cls = method.__globals__.get(class_name)
if isinstance(cls, type):
return cls
# method is a module-level function
return inspect.getmodule(method)
def to_metadata_string(obj: Any) -> str:
"""
Creates a string that helps humans understand where the given object comes from. Examples::
to_metadata_string(func_thread.run) == "function(localstack.utils.threads:FuncThread.run)"
:param obj: a class, module, method, function or object
:return: a string representing the objects origin
"""
if inspect.isclass(obj):
return f"class({obj.__module__}:{obj.__name__})"
if inspect.ismodule(obj):
return f"module({obj.__name__})"
if inspect.ismethod(obj):
return f"method({obj.__module__}:{obj.__qualname__})"
if inspect.isfunction(obj):
# TODO: distinguish bound method
return f"function({obj.__module__}:{obj.__qualname__})"
if isinstance(obj, object):
return f"object({obj.__module__}:{obj.__class__.__name__})"
return str(obj)
def create_patch_proxy(target: Callable, new: Callable):
"""
Creates a proxy that calls `new` but passes as first argument the target.
"""
@functools.wraps(target)
def proxy(*args, **kwargs):
if _is_bound_method:
# bound object "self" is passed as first argument if this is a bound method
args = args[1:]
return new(target, *args, **kwargs)
# keep track of the real proxy subject (i.e., the new function that is used as patch)
proxy.__subject__ = new
_is_bound_method = inspect.ismethod(target)
if _is_bound_method:
proxy = types.MethodType(proxy, target.__self__)
return proxy
class Patch:
applied_patches: list["Patch"] = []
"""Bookkeeping for patches that are applied. You can use this to debug patches. For instance,
you could write something like::
for patch in Patch.applied_patches:
print(patch)
Which will output in a human readable format information about the currently active patches.
"""
obj: Any
name: str
new: Any
def __init__(self, obj: Any, name: str, new: Any) -> None:
super().__init__()
self.obj = obj
self.name = name
try:
self.old = getattr(self.obj, name)
except AttributeError:
self.old = None
self.new = new
self.is_applied = False
def apply(self):
if self.is_applied:
return
if self.old and self.name == "__getattr__":
raise Exception("You can't patch class types implementing __getattr__")
if not self.old and self.name != "__getattr__":
raise AttributeError(f"`{self.obj.__name__}` object has no attribute `{self.name}`")
setattr(self.obj, self.name, self.new)
Patch.applied_patches.append(self)
self.is_applied = True
def undo(self):
if not self.is_applied:
return
# If we added a method to a class type, we don't have a self.old. We just delete __getattr__
setattr(self.obj, self.name, self.old) if self.old else delattr(self.obj, self.name)
Patch.applied_patches.remove(self)
self.is_applied = False
def __enter__(self):
self.apply()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.undo()
return self
@staticmethod
def extend_class(target: type, fn: Callable):
def _getattr(obj, name):
if name != fn.__name__:
raise AttributeError(f"`{target.__name__}` object has no attribute `{name}`")
return functools.partial(fn, obj)
return Patch(target, "__getattr__", _getattr)
@staticmethod
def function(target: Callable, fn: Callable, pass_target: bool = True):
obj = get_defining_object(target)
name = target.__name__
is_class_instance = not inspect.isclass(obj) and not inspect.ismodule(obj)
if is_class_instance:
# special case: If the defining object is not a class, but a class instance,
# then we need to bind the patch function to the target object. Also, we need
# to ensure that the final patched method has the same name as the original
# method on the defining object (required for restoring objects with patched
# methods from persistence, to avoid AttributeError).
fn.__name__ = name
fn = types.MethodType(fn, obj)
if pass_target:
new = create_patch_proxy(target, fn)
else:
new = fn
return Patch(obj, name, new)
def __str__(self):
try:
# try to unwrap the original underlying function that is used as patch (basically undoes what
# ``create_patch_proxy`` does)
new = self.new.__subject__
except AttributeError:
new = self.new
old = self.old
return f"Patch({to_metadata_string(old)} -> {to_metadata_string(new)}, applied={self.is_applied})"
class Patches:
patches: list[Patch]
def __init__(self, patches: list[Patch] = None) -> None:
super().__init__()
self.patches = []
if patches:
self.patches.extend(patches)
def apply(self):
for p in self.patches:
p.apply()
def undo(self):
for p in self.patches:
p.undo()
def __enter__(self):
self.apply()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.undo()
def add(self, patch: Patch):
self.patches.append(patch)
def function(self, target: Callable, fn: Callable, pass_target: bool = True):
self.add(Patch.function(target, fn, pass_target))
def patch(target, pass_target=True):
"""
Function decorator to create a patch via Patch.function and immediately apply it.
Example::
def echo(string):
return "echo " + string
@patch(target=echo)
def echo_uppercase(target, string):
return target(string).upper()
echo("foo")
# will print "ECHO FOO"
echo_uppercase.patch.undo()
echo("foo")
# will print "echo foo"
When you are patching classes, with ``pass_target=True``, the unbound function will be passed as the first
argument before ``self``.
For example::
@patch(target=MyEchoer.do_echo, pass_target=True)
def my_patch(fn, self, *args):
return fn(self, *args)
@patch(target=MyEchoer.do_echo, pass_target=False)
def my_patch(self, *args):
...
This decorator can also patch a class type with a new method.
For example:
@patch(target=MyEchoer)
def new_echo(self, *args):
...
:param target: the function or method to patch
:param pass_target: whether to pass the target to the patching function as first parameter
:returns: the same function, but with a patch created
"""
@functools.wraps(target)
def wrapper(fn):
fn.patch = (
Patch.extend_class(target, fn)
if inspect.isclass(target)
else Patch.function(target, fn, pass_target=pass_target)
)
fn.patch.apply()
return fn
return wrapper