patch 9.1.0784: there are several problems with python 3.13

Problem:  there are several problems with python 3.13
Solution: fix the problems in the python3 interface (Boris Staletic)

This commit does the following things:
1) Since python 3.13.0b1, all statically defined objects are "immortal".
   Besides never getting garbage collected, this also affects reference
   counting:

   - Immportal objects have a reference count of 2^32-1.
   - Reference counting is a no-op.

   All this is considered implementation details by cpython, so
   documentation is next to non-existent.

   Relevant CPython source code:
   https://github.com/python/cpython/blob/v3.13.0/Include/object.h#L62-L107
   https://github.com/python/cpython/blob/v3.13.0/Include/object.h#L389-L391

2) Opt-out of ANSI-painted python stack traces

3) Make python error message severity more consistent

fixes: #15838
closes: #15842

Signed-off-by: Boris Staletic <boris.staletic@protonmail.com>
Signed-off-by: puremourning <puremourning@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/if_py_both.h

@@ -635,13 +635,14 @@ PythonIO_Flush(void)
     if (old_fn != NULL && io_ga.ga_len > 0)
     {
 	((char *)io_ga.ga_data)[io_ga.ga_len] = NUL;
+	// We don't know what emsg_severe should be here, so ... hope?
 	old_fn((char *)io_ga.ga_data);
     }
     io_ga.ga_len = 0;
 }
 
     static void
-writer(writefn fn, char_u *str, PyInt n)
+writer(writefn fn, char_u *str, PyInt n, int severe)
 {
     char_u *ptr;
 
@@ -665,6 +666,7 @@ writer(writefn fn, char_u *str, PyInt n)
 
 	mch_memmove(((char *)io_ga.ga_data) + io_ga.ga_len, str, (size_t)len);
 	((char *)io_ga.ga_data)[io_ga.ga_len + len] = NUL;
+	emsg_severe = severe;
 	fn((char *)io_ga.ga_data);
 	str = ptr + 1;
 	n -= len + 1;
@@ -692,9 +694,7 @@ write_output(OutputObject *self, PyObject *string)
 
     Py_BEGIN_ALLOW_THREADS
     Python_Lock_Vim();
-    if (error)
+    writer((writefn)(error ? emsg : msg), (char_u *)str, len, error);
-	emsg_severe = TRUE;
-    writer((writefn)(error ? emsg : msg), (char_u *)str, len);
     Python_Release_Vim();
     Py_END_ALLOW_THREADS
     PyMem_Free(str);

src/if_python3.c

@@ -1338,6 +1338,11 @@ Python3_Init(void)
 	    goto fail;
 	}
 #endif
+	// Python 3.13 introduced a really useful feature: colorized exceptions.
+	// This is great if you're reading them from the terminal, but useless
+	// and broken everywhere else (such as in log files, or text editors).
+	// Opt out, forcefully.
+	vim_setenv((char_u*)"PYTHON_COLORS", (char_u*)"0");
 
 	init_structs();
 

src/testdir/test_python3.vim

@@ -4052,7 +4052,11 @@ func Test_python3_iter_ref()
 
   call assert_equal(1, g:list_iter_ref_count_increase)
   call assert_equal(1, g:dict_iter_ref_count_increase)
+  if py3eval('sys.version_info[:2] < (3, 13)')
     call assert_equal(1, g:bufmap_iter_ref_count_increase)
+  else
+    call assert_equal(0, g:bufmap_iter_ref_count_increase)
+  endif
   call assert_equal(1, g:options_iter_ref_count_increase)
 endfunc
 

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    784,
 /**/
     783,
 /**/