quote string values in empty assertion failures

[Bojun-Vvibe]

Repo: stretchr/testify (⭐ 23000)
Type: bugfix
Files changed: 2
Lines: +20/-22

What

This change updates assert.Empty and assert.NotEmpty to quote string values in failure messages, including aliased string types. The related assert package tests were updated so whitespace-only, newline-containing, and empty-string cases now assert against explicit, readable output like "\\n" and "" instead of visually ambiguous raw text.

Why

Current failure output for string values uses %v, which makes empty strings and whitespace-heavy strings hard to distinguish from formatting noise. That weakens assertion diagnostics in exactly the cases where users need clarity. Quoting string values keeps behavior unchanged while making failures immediately understandable and resolves the existing TODO-marked test expectations around these messages.

Testing

Ran GOCACHE=$(pwd)/.gocache go test ./assert -run 'Test(Empty|NotEmpty)$' from the repo root. The targeted tests passed.

Risk

Low / Message formatting only changes for string values in Empty and NotEmpty; assertion semantics are unchanged.

[dolmen]

Changes should happen in truncatingFormat.

[Bojun-Vvibe]

Thanks for the review @dolmen. To make sure I move this in the right direction — did you mean: (a) have truncatingFormat itself detect string values and switch the verb to %q automatically (so callers don't need to choose), or (b) keep the per-call-site verb but drop the formatEmptyMessageValue helper and just inline a truncatingFormat("%q", obj) call in Empty/NotEmpty? I lean toward (b) since truncatingFormat is also called with %v and %#v in many places where auto-quoting strings would be a behavior change, but happy to do (a) if you prefer the centralization. Will push the update once you confirm.