bug#53808: 29.0.50; ansi colorization process could block indefinetly on stray ESC char

[Ioannis Kappas <ioannis.kappas@gmail.com>]

On Sat, Feb 5, 2022 at 9:56 PM Lars Ingebrigtsen <larsi@gnus.org> wrote:
>
> Ioannis Kappas <ioannis.kappas@gmail.com> writes:
>
> > A solution (open to discussion) could be to identify a partial SGR
> > fragment based on its actual specification rather than only starting
> > with the ESC char:
>
> Hm...  what happens if the ESC arrives in one chunk and then the rest of
> the SGR sequence in the next chunk?

It is handled correctly as expected if the concatenated sequence is an
SGR, it is output as such, i.e. all
test/lisp/ansi-color-tests.el:ansi-color-incomplete-sequences-test
pass still pass.

Here is the list of unit tests showing of what I consider correct
handling of non SGR sequences I have came up with thus far

(ert-deftest ansi-color-context-non-sgr ()

  (with-temp-buffer
    (let ((text (ansi-color-apply "\e[33mHello World\e[0m")))
      (should (string= "Hello World" text))
      (should (equal (get-char-property 0 'font-lock-face text)
                     '(:foreground "yellow3")))
      ))

  (with-temp-buffer
    (let ((pretext (ansi-color-apply "5"))
          (text (ansi-color-apply "\e[33mHello World\e[0m")))
      (should (string= "Hello World" text))
      (should (equal (get-char-property 0 'font-lock-face text)
                     '(:foreground "yellow3")))
      ))

  (with-temp-buffer
    (let ((pretext (ansi-color-apply "\e"))
          (text (ansi-color-apply "\e[33mHello World\e[0m")))
      (should (string= "\eHello World" text))
      (should (equal (get-char-property 1 'font-lock-face text)
                     '(:foreground "yellow3")))
      ))

  (with-temp-buffer
    (let ((pretext (ansi-color-apply "\e["))
          (text (ansi-color-apply "\e[33mHello World\e[0m")))
      (should (string= "\e[Hello World" text))
      (should (equal (get-char-property 2 'font-lock-face text)
                     '(:foreground "yellow3")))
      ))

  (with-temp-buffer
    (let ((pretext (ansi-color-apply "\e[33"))
          (text (ansi-color-apply "mHello World\e[0m")))
      (should (string= "Hello World" text))
      (should (equal (get-char-property 2 'font-lock-face text)
                     '(:foreground "yellow3")))
      ))

  (with-temp-buffer
    (let ((pretext (ansi-color-apply "\e[33m"))
          (text (ansi-color-apply "Hello World\e[0m")))
      (should (string= "Hello World" text))
      (should (equal (get-char-property 2 'font-lock-face text)
                     '(:foreground "yellow3")))
      ))
  (with-temp-buffer
    (let ((pretext (ansi-color-apply "\e[33;1"))
          (text (ansi-color-apply "mHello World\e[0m")))
      (should (string= "Hello World" text))
      (should (equal (get-char-property 2 'font-lock-face text)
                     '(ansi-color-bold (:foreground "yellow3"))))
      ))

  (with-temp-buffer
    (let ((pretext (ansi-color-apply "\e[33;"))
          (text (ansi-color-apply "1mHello World\e[0m")))
      (should (string= "Hello World" text))
      (should (equal (get-char-property 2 'font-lock-face text)
                     '(ansi-color-bold (:foreground "yellow3"))))
      ))
  )

> (Miha has done work in this area recently; added to the CCs.)

Looking forward to his feedback :) it is because of his work I've
decided to raise this against 29 instead of the 28 branch.