Cannot manually install extension in Caja 1.20.2

[jondo]

I am on Linux Mint 19.1 MATE 64-bit.
I have followed the instructions on 'how to manually install a python extension', for the installation of the manually-downloaded kdiff3-compare.py. I would now expect this extension to show up in Caja's Preferences->Extensions, but it doesn't.
(I notice, however, that a file kdiff3-compare.pyc gets created automatically.)

[giuspen]

Have you selected one or two files before right clicking?

[jondo]

Yes, but there is no diff-related context menu entry.
But shouldn't the extension show up in Caja's extension list?
Has someone else got kdiff3-compare.py working with Linux Mint 19.1 MATE 64-bit?

[giuspen]

Just tried on ubuntu mate 18.04 and it works perfectly

[jondo]

I know that it's some work, but could you be so nice and try my Linux Mint version (in a VM)?

Also, should the extension show up in Caja's extension list?

[bttrx]

It's an old issue, but I tried to figure it out just to learn something.

I know that it's some work, but could you be so nice and try my Linux Mint version (in a VM)?

I did my research with Linux Mint 19.3 MATE 32-bit with Caja 1.22.2.

Also, should the extension show up in Caja's extension list?

Yes, it should. It doesn't, because of different Python versions.

In ~/.xsession-errors you will probably spot:

Traceback (most recent call last):
  File "/home/YOURUSER/.local/share/caja-python/extensions/kdiff3-compare.py", line 26, in <module>
    import urllib.parse, os, subprocess, re
ImportError: No module named parse

I guess, you ran kdiff3-compare.py version 3.6. This requires Python3, but Mint 19.x defaults to Python2. So either run kdiff3-compare.py version 3.4 (from caja-pyextensions-3.4.1.tar.xz) or apply these changes to version 3.6:

--- kdiff3-compare.py.bak	2021-02-25 22:48:53.000000000 +0100
+++ kdiff3-compare.py	2025-01-14 22:44:33.735048727 +0100
@@ -21,11 +21,11 @@
 #   MA 02110-1301, USA.
 
 import gi
 gi.require_version('Caja', '2.0')
 from gi.repository import Caja, GObject, Gtk, GdkPixbuf
-import urllib.parse, os, subprocess, re
+import urllib, os, subprocess, re
 import locale, gettext
 
 APP_NAME = "caja-pyextensions"
 LOCALE_PATH = "/usr/share/locale/"
 NAUPYEXT_KDIFF3 = 'NAUPYEXT_KDIFF3'
@@ -69,15 +69,15 @@ class Kdiff3Actions(GObject.GObject, Caj
            connects its 'activate' signal to the 'run' method passing the list of selected Audio items"""
         num_paths = len(sel_items)
         if num_paths == 0 or num_paths > 2: return
         uri_raw = sel_items[0].get_uri()
         if len(uri_raw) < 7: return
-        element_1 = urllib.parse.unquote(uri_raw[7:])
+        element_1 = urllib.unquote(uri_raw[7:])
         if num_paths == 2:
             uri_raw = sel_items[1].get_uri()
             if len(uri_raw) < 7: return
-            element_2 = urllib.parse.unquote(uri_raw[7:])
+            element_2 = urllib.unquote(uri_raw[7:])
             if os.path.isfile(element_1):
                 if not os.path.isfile(element_2): return
                 if not self._is_text_document(element_1): return
                 if not self._is_text_document(element_2): return
             elif os.path.isdir(element_1):

Now in ~/.xsession-errors you see:

RuntimeError: object at 0xb0d9270c of type Kdiff3Actions is not initialized

We insert a new line GObject.Object.__init__(self) and the patch will become:

--- kdiff3-compare.py.bak	2021-02-25 22:48:53.000000000 +0100
+++ kdiff3-compare.py	2025-01-14 23:18:53.613633740 +0100
@@ -21,11 +21,11 @@
 #   MA 02110-1301, USA.
 
 import gi
 gi.require_version('Caja', '2.0')
 from gi.repository import Caja, GObject, Gtk, GdkPixbuf
-import urllib.parse, os, subprocess, re
+import urllib, os, subprocess, re
 import locale, gettext
 
 APP_NAME = "caja-pyextensions"
 LOCALE_PATH = "/usr/share/locale/"
 NAUPYEXT_KDIFF3 = 'NAUPYEXT_KDIFF3'
@@ -41,10 +41,11 @@ _ = gettext.gettext
 class Kdiff3Actions(GObject.GObject, Caja.MenuProvider):
     """Implements the 'Kdiff3 Compare' extension to the Caja right-click menu"""
 
     def __init__(self):
         """Caja crashes if a plugin doesn't implement the __init__ method"""
+        GObject.Object.__init__(self)
         try:
             factory = Gtk.IconFactory()
             pixbuf = GdkPixbuf.Pixbuf.new_from_file(ICONPATH)
             iconset = Gtk.IconSet.new_from_pixbuf(pixbuf)
             factory.add("kdiff3", iconset)
@@ -69,15 +70,15 @@ class Kdiff3Actions(GObject.GObject, Caj
            connects its 'activate' signal to the 'run' method passing the list of selected Audio items"""
         num_paths = len(sel_items)
         if num_paths == 0 or num_paths > 2: return
         uri_raw = sel_items[0].get_uri()
         if len(uri_raw) < 7: return
-        element_1 = urllib.parse.unquote(uri_raw[7:])
+        element_1 = urllib.unquote(uri_raw[7:])
         if num_paths == 2:
             uri_raw = sel_items[1].get_uri()
             if len(uri_raw) < 7: return
-            element_2 = urllib.parse.unquote(uri_raw[7:])
+            element_2 = urllib.unquote(uri_raw[7:])
             if os.path.isfile(element_1):
                 if not os.path.isfile(element_2): return
                 if not self._is_text_document(element_1): return
                 if not self._is_text_document(element_2): return
             elif os.path.isdir(element_1):