python.el: Adjustments to Flymake backend

* lisp/progmodes/python (python-flymake-command): Advertise possiblity
to use pylint.
(python-flymake-command-output-pattern): Make compatible with recent
versions of pyflakes.  (Bug#53913)

2 files changed, 43 insertions, 5 deletions

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 285a57348e0..5fffb4b7d3d 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -5648,9 +5648,13 @@ returned as is."
 This is a non empty list of strings, the checker tool possibly followed by
 required arguments.  Once launched it will receive the Python source to be
 checked as its standard input.
-To use `flake8' you would set this to (\"flake8\" \"-\")."
+To use `flake8' you would set this to (\"flake8\" \"-\").
+To use `pylint' you would set this to (\"pylint\" \"--from-stdin\" \"stdin\")."
   :version "26.1"
-  :type '(repeat string))
+  :type '(choice (const :tag "Pyflakes" ("pyflakes"))
+                 (const :tag "Flake8" ("flake8" "-"))
+                 (const :tag "Pylint" ("pylint" "--from-stdin" "stdin"))
+                 (repeat :tag "Custom command" string)))
 
 ;; The default regexp accommodates for older pyflakes, which did not
 ;; report the column number, and at the same time it's compatible with
@@ -5658,7 +5662,7 @@ To use `flake8' you would set this to (\"flake8\" \"-\")."
 ;; TYPE
 (defcustom python-flymake-command-output-pattern
   (list
-   "^\\(?:<?stdin>?\\):\\(?1:[0-9]+\\):\\(?:\\(?2:[0-9]+\\):\\)? \\(?3:.*\\)$"
+   "^\\(?:<?stdin>?\\):\\(?1:[0-9]+\\):\\(?:\\(?2:[0-9]+\\):?\\)? \\(?3:.*\\)$"
    1 2 nil 3)
   "Specify how to parse the output of `python-flymake-command'.
 The value has the form (REGEXP LINE COLUMN TYPE MESSAGE): if
@@ -5670,7 +5674,6 @@ MESSAGE'th gives the message text itself.
 If COLUMN or TYPE are nil or that index didn't match, that
 information is not present on the matched line and a default will
 be used."
-  :version "26.1"
   :type '(list regexp
                (integer :tag "Line's index")
                (choice
@@ -5679,7 +5682,8 @@ be used."
                (choice
                 (const :tag "No type" nil)
                 (integer :tag "Type's index"))
-               (integer :tag "Message's index")))
+               (integer :tag "Message's index"))
+  :version "29.1")
 
 (defcustom python-flymake-msg-alist
   '(("\\(^redefinition\\|.*unused.*\\|used$\\)" . :warning))
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index 0904dfc9639..a11716a7b53 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -6300,6 +6300,40 @@ buffer with overlapping strings."
     a = 1
 ")))
 
+
+;;; Flymake
+
+(ert-deftest python-tests--flymake-command-output-pattern ()
+  (pcase-let ((`(,patt ,line ,col ,type ,msg)
+               python-flymake-command-output-pattern))
+    ;; Pyflakes output as of version 2.4.0
+    (let ((output "<stdin>:12:34 'a.b.c as d' imported but unused"))
+      (string-match patt output)
+      (should (equal (match-string line output) "12"))
+      (when col (should (equal (match-string col output) "34")))
+      (should (equal (match-string msg output)
+                     "'a.b.c as d' imported but unused")))
+    ;; Flake8 output as of version 4.0.1
+    (let ((output "stdin:12:34: F401 'a.b.c as d' imported but unused"))
+      (string-match patt output)
+      (should (equal (match-string line output) "12"))
+      (when col (should (equal (match-string col output) "34")))
+      (when type (should (equal (match-string type output) "F401")))
+      (should (equal (match-string msg output)
+                     (if type
+                         "'a.b.c as d' imported but unused"
+                       "F401 'a.b.c as d' imported but unused"))))
+    ;; Pylint output as of version 2.14.5
+    (let ((output "stdin:12:34: W0611: Unused import a.b.c (unused-import)"))
+      (string-match patt output)
+      (should (equal (match-string line output) "12"))
+      (when col (should (equal (match-string col output) "34")))
+      (when type (should (equal (match-string type output) "W0611")))
+      (should (equal (match-string msg output)
+                     (if type
+                         "Unused import a.b.c (unused-import)"
+                       "W0611: Unused import a.b.c (unused-import)"))))))
+
 (provide 'python-tests)
 
 ;;; python-tests.el ends here