rust-lang / rust-lang/rustfmt

max_width is not stable/deterministic

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#5,743 2 comments 0 reactions 0 assignees View on GitHub

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C-bug I-non-idempotency P-low SO-max_width
Dominant language
Rust
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Forks
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Avg merge
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Merged PRs (30d)
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Description

If I have a repo that uses rustfmt defaults, (e.g. max_width=100), I can run

 cargo fmt -- --config max_width=100
 cargo fmt -- --config max_width=80
 cargo fmt -- --config max_width=100

which will not restore the code to its original formatting but leave some modifications in place.
(for example seen on the cargo repo)

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Research direction

Reproduce the reported sequence in a Rust repository such as cargo: run cargo fmt with max_width=100, then 80, then 100 again, and compare the result with the original formatting. Investigate why the final formatting is not restored; done means repeated configuration changes produce deterministic output.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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