Simplify ChannelUnavailable APIError handling with let-else

[Abeeujah]

e9e3060 Fixes the TODO for the error handling.
3d6a879 Fixes the triggered manual_str_repeat lint.

[ldk-reviews-bot]

I've assigned @valentinewallace as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[ldk-claude-review-bot]

The code matches my prior review exactly and remains clean.

No issues found.

The PR is correct and behavior-preserving:

• channelmanager.rs:11468-11473 — the let-else refactor is equivalent to the original match. handle_error is a map_err wrapper that always returns Err for Err input, so .unwrap_err() cannot panic; res remains owned in the else block since a failed let-else match moves nothing, making res.map(|_| ()) valid.
• channelmanager.rs:19832 — dropping the now-unused Hasher import is correct.

[Hamza1610]

Test Results: PASS

All tests passed successfully! However, there are a couple of minor warnings to address:

** Redundant Import in channelmanager.rs**
warning: the item Hasher is imported redundantly
--> lightning/src/ln/channelmanager.rs:19832:35
|
177 | use core::hash::{Hash, Hasher};
| ------ the item Hasher is already imported here
19832 | use core::hash::{BuildHasher, Hasher};
| ^^^^^^

Issue: Hasher is imported twice in the same file. Fix: Remove the redundant Hasher from line 19832, keeping only BuildHasher: use core::hash::{BuildHasher};

Overall: Tests pass |Only minor cleanup needed

[Hamza1610]

When I was testing I noticed some ignored test. These might be deprecated test that are not in used anymore. I'm suggesting to create a new PR for this. @casey what do you think about that.

[Abeeujah]

use core::hash::{Hash, Hasher};

Hi @Hamza1610

I appreciate the review! However, the unused import warning is actually unrelated to the changes in this PR. It looks like it was introduced to main in commit a1ad1a3

Given the ongoing Forgejo migration (#4734), it's probably best to avoid scope creep here to keep this PR clean and prevent untracked changes.

[Hamza1610]

Yes, you are right, PR has be be clean. Thanks for highlighting this.

[valentinewallace]

Looks good! Second commit is redundant with #4727

[Abeeujah]

Second commit is redundant with #4727

@valentinewallace thanks for the review, I've dropped the commit, and addressed the duplicate import warning.

[valentinewallace]

Looks like the second commit is still there?

[Abeeujah]

Looks like the second commit is still there?

My Bad, it's not anymore; Successfully dropped the commit via rebase.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.90%. Comparing base (b6f3ad7) to head (b4f7416).
⚠️ Report is 3215 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4736      +/-   ##
==========================================
+ Coverage   84.54%   86.90%   +2.35%     
==========================================
  Files         137      161      +24     
  Lines       77617   111680   +34063     
  Branches    77617   111680   +34063     
==========================================
+ Hits        65625    97051   +31426     
- Misses       9949    12121    +2172     
- Partials     2043     2508     +465     

Flag	Coverage Δ
fuzzing-fake-hashes	7.77% <0.00%> (?)
fuzzing-real-hashes	29.82% <20.00%> (?)
tests	86.24% <100.00%> (?)

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