manual-result-tap

Prefer Result tap methods when mapping observes and returns its payload

Mapping a Result payload only to observe it before returning it unchanged obscures the side effect.
Instead, you SHOULD use tap for successful values and tapErr for errors.

- Category: style
- Level: warning
- Fix: automatic
- Scope: module

Reported

declare function record(value: &readonly int32): void;

function inspect(result: Result<int32, string>): Result<int32, string> {
    return result.map((value) => {
        record(value);
        value
    });
}
Accepted

declare function record(value: &readonly int32): void;

function inspect(result: Result<int32, string>): Result<int32, string> {
    return result.tap((value) => {
        record(value);
    });
}
Prior art

- Clippy · manualinspect

language/linter/src/rules/style/manualresulttap.rs:8