Patching a class method

[davidkrisch]

I'm having trouble getting a "Hello Patchy" example working - patching a class method is specifically what I would like to do. I am working towards using patchy to apply a single line patch to django.contrib.sites.SiteManager.get_current in Django 1.8.

Thank you in advance for any guidance...

hello.py

class Hello(object):
    def say(self):
        return "Hey"

hello2.py

def say(self):
    return "Hello"

To get the diff I did

$ diff -u hello.py hello2.py
--- hello.py    2016-09-14 12:44:38.000000000 -1000
+++ hello2.py   2016-09-14 13:11:13.000000000 -1000
@@ -1,3 +1,2 @@
-class Hello(object):
-    def say(self):
-        return "Hey"
+def say(self):
+    return "Hello"

Then I apply the patch in main.py

import patchy

from hello import Hello

patchy.patch(Hello.say, '''\
    --- hello.py          2016-09-14 12:44:38.000000000 -1000
    +++ hello2.py   2016-09-14 13:11:13.000000000 -1000
    @@ -1,3 +1,2 @@
    -class Hello(object):
    -    def say(self):
    -        return "Hey"
    +def say(self):
    +    return "Hello"
    ''')

h = Hello()
print h.say()

I get the following error

ValueError: Could not apply the patch to 'say'. The message from `patch` was:
patching file /var/folders/wb/ylzhww1j12zcq32hbr7q7mt80000gp/T/patchym8Kcyv/say.py
Hunk #1 FAILED at 1.
1 out of 1 hunk FAILED -- saving rejects to file /var/folders/wb/ylzhww1j12zcq32hbr7q7mt80000gp/T/patchym8Kcyv/say.py.rej


The code to patch was:
def say(self):
    return "Hey"

The patch was:
--- hello.py    2016-09-14 12:44:38.000000000 -1000
+++ hello2.py    2016-09-14 13:11:13.000000000 -1000
@@ -1,3 +1,2 @@
-class Hello(object):
-    def say(self):
-        return "Hey"
+def say(self):
+    return "Hello"

What am I doing wrong? (thank you)

[davidkrisch]

Got it! I read the README a little closer and figured it out. The diff shouldn't include the original file.

hello.py

class Hello(object):
    def say(self):
        return "Hey"

hello1.py

def say(self):
    return "Hey"

hello2.py

def say(self):
    return "Hello"

To get the diff...

$ diff -u hello1.py hello2.py
--- hello1.py   2016-09-14 13:32:53.000000000 -1000
+++ hello2.py   2016-09-14 13:11:13.000000000 -1000
@@ -1,2 +1,2 @@
 def say(self):
-    return "Hey"
+    return "Hello"

main.py

import patchy
from hello import Hello

patchy.patch(Hello.say, '''\
    @@ -1,2 +1,2 @@
     def say(self):
    -    return "Hey"
    +    return "Hello"
    ''')

h = Hello()
print h.say()

Running main.py works!

$ python main.py
Hello

[adamchainz]

That's it! Yup patchy operates only on a function basis so including the class definition screws it up.