Summary
fmterrorfnoverbs decides whether a fmt.Errorf format string contains a real verb with a bare strings.Contains(val, "%") substring test. An escaped literal percent %% contains a % but is not a format verb, so fmt.Errorf("... %% ...") with no other verb is wrongly treated as "has a verb" and is not flagged — a false negative. The idiomatic rewrite errors.New("... % ...") is missed.
Location
pkg/linters/fmterrorfnoverbs/fmterrorfnoverbs.go:58-69
val := lit.Value
if len(val) >= 2 {
val = val[1 : len(val)-1]
}
if !strings.Contains(val, "%") { // %% contains '%' => skipped, but %% is NOT a verb
... report ...
}Evidence / repro
// not flagged today, but has no real verb — equivalent to errors.New("disk usage exceeds 90% limit")
return fmt.Errorf("disk usage exceeds 90%% limit")val is disk usage exceeds 90%% limit; strings.Contains(val, "%") is true, so the linter skips it. There is no real verb — %% renders as a literal %.
A secondary, lower-frequency miss: the check runs on the raw literal (quotes stripped, escapes not decoded), so a verb expressed as an escape (e.g. "\u0025d") is also mis-classified. The %% case is the realistic one.
Impact
False negative only (no false positive, no autofix risk — the linter emits no SuggestedFix). fmterrorfnoverbs is one of the CI-enforced linters, so closing the gap improves enforcement precision. Frequency is low (no-verb fmt.Errorf whose only % is an escaped %%), but the fix is small and removes a clear correctness gap.
Recommendation
Replace the strings.Contains(val, "%") heuristic with a scan that skips %% pairs before deciding whether a real verb is present — e.g. walk the decoded string and treat %% as two literal characters, reporting when no non-%% %-directive remains. The same %%-aware scan already exists in spirit in the verb-handling logic referenced by #40434 (sprintferrdot) and #38788 (hardcodedfilepath); reuse that approach for consistency.
Before / after intent
- Before:
Contains("%") → any % (including %%) suppresses the report.
- After: strip
%% pairs first; report when the remaining string has no %.
Validation checklist
Effort
Low — single-function change in run, ~5 lines plus testdata.
Sergo R49 — fresh deep-audit of fmterrorfnoverbs (type-resolved IsFmtErrorf and nolint are correct; only the verb-presence test is too coarse).
Generated by 🤖 Sergo - Serena Go Expert · 231.1 AIC · ⌖ 14.3 AIC · ⊞ 5.9K · ◷
Summary
fmterrorfnoverbsdecides whether afmt.Errorfformat string contains a real verb with a barestrings.Contains(val, "%")substring test. An escaped literal percent%%contains a%but is not a format verb, sofmt.Errorf("... %% ...")with no other verb is wrongly treated as "has a verb" and is not flagged — a false negative. The idiomatic rewriteerrors.New("... % ...")is missed.Location
pkg/linters/fmterrorfnoverbs/fmterrorfnoverbs.go:58-69Evidence / repro
valisdisk usage exceeds 90%% limit;strings.Contains(val, "%")is true, so the linter skips it. There is no real verb —%%renders as a literal%.A secondary, lower-frequency miss: the check runs on the raw literal (quotes stripped, escapes not decoded), so a verb expressed as an escape (e.g.
"\u0025d") is also mis-classified. The%%case is the realistic one.Impact
False negative only (no false positive, no autofix risk — the linter emits no
SuggestedFix).fmterrorfnoverbsis one of the CI-enforced linters, so closing the gap improves enforcement precision. Frequency is low (no-verbfmt.Errorfwhose only%is an escaped%%), but the fix is small and removes a clear correctness gap.Recommendation
Replace the
strings.Contains(val, "%")heuristic with a scan that skips%%pairs before deciding whether a real verb is present — e.g. walk the decoded string and treat%%as two literal characters, reporting when no non-%%%-directive remains. The same%%-aware scan already exists in spirit in the verb-handling logic referenced by #40434 (sprintferrdot) and #38788 (hardcodedfilepath); reuse that approach for consistency.Before / after intent
Contains("%")→ any%(including%%) suppresses the report.%%pairs first; report when the remaining string has no%.Validation checklist
fmt.Errorf("90%% done")(no other verb) is flagged.fmt.Errorf("%d%% done", n)(real verb present) is NOT flagged.fmt.Errorf("plain message")still flagged;fmt.Errorf("value=%s", v)still skipped.Effort
Low — single-function change in
run, ~5 lines plus testdata.Sergo R49 — fresh deep-audit of
fmterrorfnoverbs(type-resolvedIsFmtErrorfand nolint are correct; only the verb-presence test is too coarse).