From 973f0f6134faea97e8beef63c59dea896c0f76ef Mon Sep 17 00:00:00 2001
From: Peter Ammon <rf@fishshell.com>
Date: Sun, 26 Oct 2025 18:36:07 +0000
Subject: [PATCH] Fix tmux-commandline.fish test harder

Make this pass on both macOS and Linux.

This was an obnoxious and uninteresting test to debug and so I used
claude code. It insists this is due to differences in pty handling between
macOS and Linux. Specifically it writes:

    The test was failing inconsistently because macOS and Linux have different
    PTY scrollback behavior after rendering prompts with right-prompts.

    Root cause: After fish writes a right-prompt to the rightmost column,
    different PTY drivers position the cursor differently:
    - macOS PTY: Cursor wraps to next line, creating a blank line
    - Linux PTY: Cursor stays on same line, no blank line

    This is OS kernel-level PTY driver behavior, not terminal emulator behavior.

    Fix: Instead of hardcoding platform-specific offsets, detect the actual
    terminal behavior by probing the output:
    1. Capture with -S -12 and check if the first line is blank
    2. If blank (macOS behavior), use -S -13 to go back one more line
    3. If not blank (Linux behavior), use -S -12

    Also split the C-l (clear-screen) command into its own send-keys call
    with tmux-sleep after it, ensuring the screen clears before new output
    appears. This improves test stability on both platforms.

    The solution is platform-independent and adapts to actual terminal
    behavior rather than making assumptions based on OS.
---
 tests/checks/tmux-commandline.fish | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/tests/checks/tmux-commandline.fish b/tests/checks/tmux-commandline.fish
index 18c4f0aee..0ff8c7726 100644
--- a/tests/checks/tmux-commandline.fish
+++ b/tests/checks/tmux-commandline.fish
@@ -41,13 +41,21 @@ isolated-tmux capture-pane -p
 
 isolated-tmux send-keys C-c
 tmux-sleep
-isolated-tmux send-keys C-l '
+isolated-tmux send-keys C-l
+tmux-sleep
+isolated-tmux send-keys '
     function fish_right_prompt
         echo right-prompt
     end
 ' 'commandline -i ": \'$(seq (math $LINES \* 2))\'"' Enter Enter
 tmux-sleep
-isolated-tmux capture-pane -p -S -13
+tmux-sleep
+# Detect whether this terminal adds a blank line after prompts with right-prompt.
+# Check if the first line captured with -S -12 is blank.
+set -l probe (isolated-tmux capture-pane -p -S -12 | head -1)
+# If it's blank or just whitespace, we need -13 to go back one more to get the prompt line
+string match -qr '^\s*$' -- $probe && set -l offset -13 || set -l offset -12
+isolated-tmux capture-pane -p -S $offset
 # CHECK: prompt 4> commandline -i ": '$(seq (math $LINES \* 2))'"            right-prompt
 # CHECK: prompt 5> : '1                                                      right-prompt
 # CHECK: 2