bug#36056: Regression? (Python Documentation String Indent In Auto Fill Mode)

[Noam Postavsky <npostavs@gmail.com>]

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Dima Kogan <dima@secretsauce.net> writes:

> This is what I'd expect. After the fix (i.e. if
> fill-indent-according-to-mode is t) I get this:
>
>
> r'''aaa
>
> this is a test this is a test this is a test this is a test this is a
>  test this is a test
>
> '''
>
>
> For some reason it now wants to add one space at the beginning of every
> line in a paragraph except the first. Is there some interpretation where
> this the "correct" behavior?

Thanks for reporting this.  The problem seems to be that fill-newline
puts the space on the new line when breaking the line, and
python-indent-line (which is called when fill-indent-according-to-mode
is t) leaves indentation inside strings as-is.

Maybe the solution is to bind fill-indent-according-to-mode only during
auto-filling?  The patch below seems to work for both this bug's OP, and
your case.


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From 46a01b97025ed2f826af4237044bad5262e06c6a Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Sun, 8 Sep 2019 10:42:19 -0400
Subject: [PATCH] Fix fill-paragraph in python docstrings (Bug#36056)

* lisp/progmodes/python.el (python-do-auto-fill): New function.
(python-mode): Set it as normal-auto-fill-function, and don't set
fill-indent-according-to-mode.  Having the latter set during
fill-paragraph gives wrongs result, because python-indent-line doesn't
remove indentation added by filling.
* test/lisp/progmodes/python-tests.el (python-fill-docstring): New
test.
---
 lisp/progmodes/python.el            |  8 +++++++-
 test/lisp/progmodes/python-tests.el | 13 ++++++++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 14b65669c4..ec5d8c5551 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -4084,6 +4084,12 @@ python-fill-paren
       (goto-char (line-end-position))))
   t)
 
+(defun python-do-auto-fill ()
+  "Like `do-auto-fill', but bind `fill-indent-according-to-mode'."
+  ;; See Bug#36056.
+  (let ((fill-indent-according-to-mode t))
+    (do-auto-fill)))
+
 \f
 ;;; Skeletons
 
@@ -5379,7 +5385,7 @@ python-mode
   (set (make-local-variable 'paragraph-start) "\\s-*$")
   (set (make-local-variable 'fill-paragraph-function)
        #'python-fill-paragraph)
-  (set (make-local-variable 'fill-indent-according-to-mode) t) ; Bug#36056.
+  (set (make-local-variable 'normal-auto-fill-function) #'python-do-auto-fill)
 
   (set (make-local-variable 'beginning-of-defun-function)
        #'python-nav-beginning-of-defun)
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index b1cf7e8806..c5ad1dfb86 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -1351,7 +1351,7 @@ python-indent-region-5
                       expected)))))
 
 \f
-;;; Autofill
+;;; Filling
 
 (ert-deftest python-auto-fill-docstring ()
   (python-tests-with-temp-buffer
@@ -1368,6 +1368,17 @@ python-auto-fill-docstring
      (forward-line 1)
      (should (= docindent (current-indentation))))))
 
+(ert-deftest python-fill-docstring ()
+  (python-tests-with-temp-buffer
+   "\
+r'''aaa
+
+this is a test this is a test this is a test this is a test this is a test this is a test.
+'''"
+   (search-forward "test.")
+   (fill-paragraph)
+   (should (= (current-indentation) 0))))
+
 \f
 ;;; Mark
 
-- 
2.11.0