python-mode: Fix detection for opening blocks.

	* python.el (python-info-dedenter-opening-block-positions): There
	can't be any back-indented lines between an opening block and the
	current line.

	* python-tests.el (python-indent-electric-colon-4): Add an indent
	test case where there is one-more indented previous opening block.

2 files changed, 39 insertions, 2 deletions

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index d8262dd0a75..90b5e4e0dc6 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -4693,7 +4693,8 @@ likely an invalid python file."
     (let ((dedenter-pos (python-info-dedenter-statement-p)))
       (when dedenter-pos
         (goto-char dedenter-pos)
-        (let* ((pairs '(("elif" "elif" "if")
+        (let* ((cur-line (line-beginning-position))
+               (pairs '(("elif" "elif" "if")
                         ("else" "if" "elif" "except" "for" "while")
                         ("except" "except" "try")
                         ("finally" "else" "except" "try")))
@@ -4709,7 +4710,22 @@ likely an invalid python file."
               (let ((indentation (current-indentation)))
                 (when (and (not (memq indentation collected-indentations))
                            (or (not collected-indentations)
-                               (< indentation (apply #'min collected-indentations))))
+                               (< indentation (apply #'min collected-indentations)))
+                           ;; There must be no line with indentation
+                           ;; smaller than `indentation' (except for
+                           ;; blank lines) between the found opening
+                           ;; block and the current line, otherwise it
+                           ;; is not an opening block.
+                           (save-excursion
+                             (forward-line)
+                             (let ((no-back-indent t))
+                               (save-match-data
+                                 (while (and (< (point) cur-line)
+                                             (setq no-back-indent
+                                                   (or (> (current-indentation) indentation)
+                                                       (python-info-current-line-empty-p))))
+                                   (forward-line)))
+                               no-back-indent)))
                   (setq collected-indentations
                         (cons indentation collected-indentations))
                   (when (member (match-string-no-properties 0)
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index 2df1bbf50d8..158c52f080c 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -1156,6 +1156,27 @@ if do:
    (python-tests-look-at "that)")
    (should (= (current-indentation) 6))))
 
+(ert-deftest python-indent-electric-colon-4 ()
+  "Test indentation case where there is one more-indented previous open block."
+  (python-tests-with-temp-buffer
+   "
+def f():
+    if True:
+        a = 5
+
+        if True:
+            a = 10
+
+        b = 3
+
+else
+"
+   (python-tests-look-at "else")
+   (goto-char (line-end-position))
+   (python-tests-self-insert ":")
+   (python-tests-look-at "else" -1)
+   (should (= (current-indentation) 4))))
+
 (ert-deftest python-indent-region-1 ()
   "Test indentation case from Bug#18843."
   (let ((contents "