fix(nvim): keep End path shortening on a char boundary

[kevin9327]

The crash

With layout.path_shorten_strategy = 'end', rendering a result whose directory
column has to be cut inside its first path component panics the Rust module when
that component is not ASCII:

thread 'path_shortening::tests::end_strategy_truncates_multibyte_first_component_on_char_boundary' (38540) panicked at crates\fff-nvim\src\path_shortening.rs:189:35:
assertion failed: self.is_char_boundary(new_len)

shorten_path reaches it whenever components[0].len() > max_size — the picker
window is narrow, or the filename is long, since path_max_width in
renderer.lua is max_width - strdisplaywidth(filename) - 1.

Root cause

PathShortenStrategy::End is the one place in the file that cuts a component
with String::truncate, which takes a byte length and panics off a char
boundary:

let mut component = component.to_string();
component.truncate(max_size);

Every other cut in this module goes through Self::truncate_str /
Self::truncate_str_keep_end, which count chars. The single-component branch
a few lines up in the same function already calls Self::truncate_str(components[0], max_size)
for exactly this situation — the multi-component branch was missed.

Chars are also the right unit here: max_size arrives from
lua/fff/picker_ui/renderer.lua as a strdisplaywidth-derived column budget,
not a byte count.

The fix

Use the existing helper, matching the sibling branch.

Verification (Windows, default ripgrep features)

RUSTUP_TOOLCHAIN was pinned to 1.98.0-x86_64-pc-windows-msvc because
rust-toolchain.toml's stable channel could not update on this machine.

New test end_strategy_truncates_multibyte_first_component_on_char_boundary
feeds документы/файл.txt (9 chars / 18 bytes in the first component) with
max_size = 15, which lands inside a character.

Before, cargo test -p fff-nvim --lib -- path_shortening:

running 9 tests

thread 'path_shortening::tests::end_strategy_truncates_multibyte_first_component_on_char_boundary' (38540) panicked at crates\fff-nvim\src\path_shortening.rs:189:35:
assertion failed: self.is_char_boundary(new_len)

test result: FAILED. 8 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out

After:

test result: ok. 9 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

The same test pins the ASCII behaviour that must not change —
core_workflow_service/db/model at max_size = 15 still yields exactly
core_workflow_s — and it passes both before and after, as does the existing
test_path_shroten_strategy_end. For ASCII the two helpers are identical, so
nothing widens.

• cargo test -p fff-nvim --lib — 9 passed, 0 failed.
• cargo fmt --all -- --check — clean.
• cargo clippy -p fff-nvim --lib — no new warnings.

Summary by CodeRabbit

• Bug Fixes
  • Improved path shortening for long paths containing multibyte UTF-8 characters.
  • Prevented characters from being split incorrectly during truncation.
  • Preserved existing behavior for ASCII-only paths.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: ee41ed14-e3e5-4f7a-b5ca-fea9b6dcb949

📥 Commits

Reviewing files that changed from the base of the PR and between 7f8537e and e702152.

📒 Files selected for processing (1)

• crates/fff-nvim/src/path_shortening.rs

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

The End path-shortening strategy now avoids splitting multibyte UTF-8 characters. A regression test covers multibyte and ASCII first components.

Changes

Path shortening

Layer / File(s)	Summary
Character-aware truncation and regression test crates/fff-nvim/src/path_shortening.rs	The End fallback uses Self::truncate_str. Tests verify character-boundary handling for "документы" and exact ASCII truncation.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to e7021

End-strategy path shortening now preserves UTF-8 character boundaries, preventing crashes for non-ASCII paths while retaining ASCII behavior. The change is ready to merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 75.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main fix: End path shortening now preserves UTF-8 character boundaries.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

• Fix all pre-merge checks with AI

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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