Making Reedline aware of the status of completors

[philocalyst]

Summary

Before

• Before, with recently added changes, reedline lied totally unaware the state of completion, as it was originally entirely tied to the its own lifecycle. With recent changes, it now has its own lifecycle, which left reedline totally in the dark, leading to poor behavior in many cases (largely in renderin).

After

• Reedline is now aware of the state a completor is in, allowing it to make rendering decisions that reflect that state.
• Flashing is now removed, which was a symptom of reedline updating under new context. It starts with that context now, and is able to respond effectively.

Additional notes

• I definitely took some liberties here in refactoring some of the impacted functions, in an effort to not let the codebase slip when adding these new conditions. The goal was to add these features will making performance better and I think I accomplished that.
• There's a corresponding PR in Nushell coming soon.
• Added a regression test for flashing.
• Biggest refactor was in create_string -- where I got both paths down to one/two allocations

[Copilot]

Pull request overview

This PR updates Reedline’s completion pipeline so the engine and menus can distinguish between pending, stale, and fresh completion results, enabling menus to avoid rendering “empty” states while background completion work is still in flight (reducing UI flashing/jumping).

Changes:

• Introduces CompletionResult/CompletionStatus and updates the Completer trait to report completion lifecycle state.
• Updates the engine loop to poll completer background work and refresh active menus when results become ready.
• Refactors IDE/columnar menu completion rendering to cache suggestion display metrics and to suppress empty-state rendering while awaiting results.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/menu/menu_functions.rs	Adds CompletionDisplay to cache suggestions and derived display metrics for menus.
src/menu/list_menu.rs	Updates completion call site to the new CompletionResult API.
src/menu/ide_menu.rs	Adopts CompletionDisplay and adds pending-aware rendering to avoid “no records” flashing.
src/menu/description_menu.rs	Updates completion call site to the new CompletionResult API.
src/menu/columnar_menu.rs	Adopts CompletionDisplay, adds pending-aware rendering, and refactors suggestion string formatting.
src/lib.rs	Re-exports new completion lifecycle types (CompletionResult, CompletionStatus, Suggestions).
src/engine.rs	Polls completion status each loop iteration and refreshes active menus when ready.
src/completion/mod.rs	Re-exports new completion lifecycle types from base.
src/completion/history.rs	Updates history completer implementation to return CompletionResult.
src/completion/default.rs	Updates default completer implementation and docs to return/use CompletionResult.
src/completion/base.rs	Adds Suggestions (Arc-backed), CompletionResult, CompletionStatus, and updates Completer trait signatures.
examples/persistent_menus.rs	Updates example completer implementation to return CompletionResult.

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[kronberger-droid]

Nice!
I hope I will get some time this week to take a closer look.

[philocalyst]

Responded to comments and made more efficent with stronger use of Arced suggestions !

[fdncred]

ok, let's continue to push forward @philocalyst to get these completions in good order. appreciate your help.