fix: --list-themes pagination

[abhinavcool42]

Fixes Issue: #3455

Bug

bat --list-themes --pager=builtin and bat --list-themes --pager=less hang after printing the first line (e.g., “Theme: 1337”). In iTerm2 the “:” prompt is hidden until resize/CR, input is in cooked mode, and display appears off-by-one.

Repro:

bat --list-themes --pager=builtin
bat --list-themes --pager=less

Root cause

• controller was creating its own pager even when an OutputHandle was already provided by the caller which led to nested pagers and TTY state confusion, manifesting as a hang and terminal not restoring properly.
• also treated stdout as “safe” when a pager was already attached, allowing clircle’s stdout identifier to be created in a pager context, which can block and contribute to the bad terminal state.

Changes

Only create OutputType when output_handle.is_none(), preventing a second pager from being started.
added attached_to_pager that is true when:

• an external OutputHandle is provided, or
• an internally created OutputType is a pager.

Route errors to the writer when attached_to_pager; otherwise use stderr.
Set stdout_identifier = None when attached_to_pager (and on Windows); otherwise use clircle::Identifier::stdout().

[keith-hall]

Thanks!

In my testing, when using this branch and doing --list-themes with less as the pager (i.e. the default setup), pressing Page Down gives some weird output (^[[6~) instead of scrolling down... Any ideas please?

[abhinavcool42]

It was caused by launching less with “quit-if-one-screen” (-F) while streaming the list-themes output in chunks. Early on, less may think the content fits on one screen and won’t enter interactive mode yet, so Page Down ends up echoing the escape sequence ^[[6~. This was confirmed by running the command bat --list-themes --pager="less -R" which avoids -F and works correctly. Changed the config.paging_mode when spawning pager to PagingMode::Always so it always stays interactive.
Also we were still adding the --no-init when we were not using --quit-if-one-screen. changed it to only add --no-init when actually using it.

[keith-hall]

I think we should respect the user's choices when they have --paging=never etc configured in the config file/env-var or specified on the command line

[abhinavcool42]

Agreed. The updated change buffers list-themes first with the existing config file, so we don’t force paging and user's choices are honored. Verified with default, --pager=less, and --paging=never.