GNU bug report logs - #78043
Cursor gets stuck after inline code input in comint buffer when using markdown-mode, bypassing prompt lines starting with '>'

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From: Kang Tu <tninja <at> gmail.com>
To: 78043 <at> debbugs.gnu.org
Subject: bug#78043: Cursor gets stuck after inline code input in comint buffer when using markdown-mode, bypassing prompt lines starting with '>'
Date: Thu, 24 Apr 2025 08:39:57 -0700

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From: Kang Tu <tninja <at> gmail.com>

To: bug-gnu-emacs <at> gnu.org
Subject: Cursor gets stuck after inline code input in comint buffer when
 using markdown-mode, bypassing prompt lines starting with '>'
Description:
 To avoid interfering with input, I implemented logic to bypass markdown
 rendering on prompt input lines, which start with '>'

 I suspect this issue is related to the interaction between markdown-mode
 rendering and comint input handling, especially regarding the bypass logic
 for prompt lines.

Environment:
 > Please refactoring `main.go`

 - Emacs version: 30.1
 - markdown-mode version: 2.5
 - OS: ubuntu 24.04 / mac osx

Attachments:
 I am using Emacs comint buffer with markdown-mode enabled to render the
 output as formatted Markdown.

 Actual behavior:
 The cursor gets stuck after inline code input on the prompt line.

 However, when I type inline code surrounded by backticks on a prompt line
 like:

 Any advice or known fixes for this interaction issue between markdown-mode
 and comint would be much appreciated.

 The cursor gets stuck after finishing the inline code and I cannot continue
 typing.

 - Minimal input example
  - Please refactoring `main.go`
 - Relevant markdown-mode and comint configuration snippets (especially
 bypass logic for prompt lines)
 (defun aider--apply-markdown-highlighting ()
  "Set up markdown highlighting for aider buffer with optimized performance.
 Ignore lines starting with '>' (command prompts/input)."
  ;; 1) Use `markdown-mode`'s syntax table:
  (set-syntax-table (make-syntax-table markdown-mode-syntax-table))
  ;; 2) For multiline constructs (like fenced code blocks), enable
 `markdown-syntax-propertize`:
  (setq-local syntax-propertize-function #'markdown-syntax-propertize)
  ;; 3) Reuse `markdown-mode`'s font-lock keywords for highlighting,
  ;;    but add a rule to prevent markdown highlighting on lines starting
 with '>'.
  (setq-local font-lock-defaults
              (list (cons
                     ;; Rule to apply default face to prompt lines, without
 overriding.
                     ;; This aims to prevent subsequent markdown rules in
 this list
                     ;; from applying, while still allowing
 comint-highlight-input.
                     '("^>.*$" 0 'default nil) ;; ==> this line did bypass
 prompt input line, update nil to t doesn't help
                     ;; Original markdown keywords
                     markdown-mode-font-lock-keywords)
                    nil ;; KEYWORDS-ONLY
                    nil ;; CASE-FOLD
                    nil ;; SYNTAX-ALIST
                    nil)) ;; SYNTAX-BEGIN
  ;; 4) Enable fenced code block highlighting, and disable special font
 processing:
  (setq-local markdown-fontify-code-blocks-natively t)
  ;; https://github.com/tninja/aider.el/issues/113
  ;; TODO: temporary solution to disable bold, italic. need a better way
 than this, if we want to keep them in reply text
  ;; Note: The rule added above is a more targeted way to handle prompts
 than disabling these globally.
  ;; Consider if these are still needed or can be re-enabled depending on
 desired appearance for non-prompt text.
  (setq-local markdown-regex-bold nil)
  (setq-local markdown-regex-italic nil)
  (setq-local markdown-regex-strike-through nil)
  ;; 5) Jit-lock and other
  (setq-local font-lock-multiline t)  ;; Handle multiline constructs
 efficiently
  (setq-local jit-lock-contextually nil)  ;; Disable contextual analysis
  (setq-local font-lock-support-mode 'jit-lock-mode)  ;; Ensure JIT lock is
 used
  (setq-local jit-lock-defer-time 0)
  ;; 6) Register font-lock explicitly:
  (font-lock-mode 1)
  ;; 7) Force immediate fontification of visible area:
  (font-lock-flush)
  (font-lock-ensure))
 - Screenshots if any

 Steps to reproduce:
 1. Open a comint buffer (e.g., shell or custom comint).
 2. Enable markdown-mode for the buffer, with special handling to skip
 rendering lines starting with '>'.
 3. In the prompt line, type an inline code snippet with backticks, e.g.:
   > Please refactoring `main.go`
 4. Observe that after typing `main.go`, the cursor is stuck and cannot
 continue.

 Expected behavior:
 The cursor should move freely and the input should work normally, with
 prompt lines properly bypassed from markdown rendering.

 Thank you!
Date: Thu, 24 Apr 2025 08:35:23 -0700
Message-ID: <87h62do9ms.fsf <at> gmail.com>

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