patch 8.0.0265: may get ml_get error when :pydo deletes lines

Problem:    May get ml_get error when :pydo deletes lines or switches to
            another buffer. (Nikolai Pavlov, issue #1421)
Solution:   Check the buffer and line every time.

src/Makefile

@@ -2168,6 +2168,8 @@ test_arglist \
 	test_popup \
 	test_profile \
 	test_put \
+	test_python2 \
+	test_python3 \
 	test_pyx2 \
 	test_pyx3 \
 	test_quickfix \

src/if_py_both.h

@@ -5619,6 +5619,7 @@ run_do(const char *cmd, void *arg UNUSED
     int		status;
     PyObject	*pyfunc, *pymain;
     PyObject	*run_ret;
+    buf_T	*was_curbuf = curbuf;
 
     if (u_save((linenr_T)RangeStart - 1, (linenr_T)RangeEnd + 1) != OK)
     {
@@ -5671,7 +5672,9 @@ run_do(const char *cmd, void *arg UNUSED
 #ifdef PY_CAN_RECURSE
 	*pygilstate = PyGILState_Ensure();
 #endif
-	if (!(line = GetBufferLine(curbuf, lnum)))
+	/* Check the line number, the command my have deleted lines. */
+	if (lnum > curbuf->b_ml.ml_line_count
+		|| !(line = GetBufferLine(curbuf, lnum)))
 	    goto err;
 	if (!(linenr = PyInt_FromLong((long) lnum)))
 	{
@@ -5684,9 +5687,19 @@ run_do(const char *cmd, void *arg UNUSED
 	if (!ret)
 	    goto err;
 
+	/* Check that the command didn't switch to another buffer. */
+	if (curbuf != was_curbuf)
+	{
+	    Py_XDECREF(ret);
+	    goto err;
+	}
+
 	if (ret != Py_None)
 	    if (SetBufferLine(curbuf, lnum, ret, NULL) == FAIL)
+	    {
+		Py_XDECREF(ret);
 		goto err;
+	    }
 
 	Py_XDECREF(ret);
 	PythonIO_Flush();

src/testdir/Make_all.mak

@@ -176,6 +176,8 @@ NEW_TESTS = test_arglist.res \
 	    test_packadd.res \
 	    test_perl.res \
 	    test_profile.res \
+	    test_python2.res \
+	    test_python3.res \
 	    test_pyx2.res \
 	    test_pyx3.res \
 	    test_quickfix.res \

src/testdir/test_python2.vim

@@ -0,0 +1,24 @@
+" Test for python 2 commands.
+" TODO: move tests from test87.in here.
+
+if !has('python')
+  finish
+endif
+
+func Test_pydo()
+  " Check deleting lines does not trigger ml_get error.
+  py import vim
+  new
+  call setline(1, ['one', 'two', 'three'])
+  pydo vim.command("%d_")
+  bwipe!
+
+  " Check switching to another buffer does not trigger ml_get error.
+  new
+  let wincount = winnr('$')
+  call setline(1, ['one', 'two', 'three'])
+  pydo vim.command("new")
+  call assert_equal(wincount + 1, winnr('$'))
+  bwipe!
+  bwipe!
+endfunc

src/testdir/test_python3.vim

@@ -0,0 +1,24 @@
+" Test for python 2 commands.
+" TODO: move tests from test88.in here.
+
+if !has('python3')
+  finish
+endif
+
+func Test_py3do()
+  " Check deleting lines does not trigger an ml_get error.
+  py3 import vim
+  new
+  call setline(1, ['one', 'two', 'three'])
+  py3do vim.command("%d_")
+  bwipe!
+
+  " Check switching to another buffer does not trigger an ml_get error.
+  new
+  let wincount = winnr('$')
+  call setline(1, ['one', 'two', 'three'])
+  py3do vim.command("new")
+  call assert_equal(wincount + 1, winnr('$'))
+  bwipe!
+  bwipe!
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    265,
 /**/
     264,
 /**/