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Reject unsafe typeof suppression in defensive.null-assumption rule #149

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Merged
alxxjohn merged 1 commit into from
Aug 19, 2026
+28 −3
Merged

Reject unsafe typeof suppression in defensive.null-assumption rule #149

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11 changes: 8 additions & 3 deletions internal/codeguard/checks/quality/quality_defensive.go
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Original file line number Diff line number Diff line change
Expand Up @@ -168,7 +168,7 @@
strings.HasSuffix(name, "row") ||
strings.Contains(name, "rowpart") ||
strings.HasSuffix(name, "part") ||
regexp.MustCompile(`part\d+$`).MatchString(name) ||

Check warning on line 171 in internal/codeguard/checks/quality/quality_defensive.go

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GitHub Actions / codeguard 

[performance.regex-compile-in-loop] regular expression compiled inside a loop; compile it once before the loop or as a package-level variable. Fix: Compile the pattern once before the loop or at package/module level and reuse it.
strings.HasSuffix(name, "context") ||
strings.HasSuffix(name, "ctx") ||
strings.Contains(name, "dto") ||
Expand Down Expand Up @@ -318,8 +318,6 @@
name + " != null",
name + " == nullptr",
name + " != nullptr",
"typeof " + name + " === ",
"typeof " + name + " == ",
}
if containsAny(loweredBody, guards) {
return true
Expand Down Expand Up @@ -356,7 +354,14 @@
}

func nullableStatementUsesOnlyNullSafeOperators(statement string, name string) bool {
return containsAny(statement, []string{name + "?.", name + "?.[", name + " ??"})
if containsAny(statement, []string{name + "?.", name + "?.[", name + " ??"}) {
return true
}
// A typeof check only narrows the value on the branch controlled by that
// check. Do not treat an arbitrary typeof occurrence elsewhere in the
// function as a null guard.
quotedName := regexp.QuoteMeta(name)
return regexp.MustCompile(`typeof\s+` + quotedName + `\s*={2,3}\s*['"](?:string|number|boolean|bigint|symbol|function)['"]\s*\?[^:]*\b` + quotedName + `(?:\.|\[)`).MatchString(statement)
}

func firstUseLine(fn precisionFunction, name string) int {
Expand Down
20 changes: 20 additions & 0 deletions tests/checks/quality_precision_followup_retune_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -406,6 +406,26 @@ func TestDefensiveNullAssumptionCreditsTypeScriptNarrowing(t *testing.T) {
assertCodeQualityRuleAbsentForPath(t, report, "defensive.null-assumption", "null-narrowing.ts:16")
}

func TestDefensiveNullAssumptionRejectsUnsafeTypeofGuards(t *testing.T) {
dir := t.TempDir()
writeFile(t, filepath.Join(dir, "packages/api/src/lib/unsafe-typeof.ts"), strings.Join([]string{
"export function objectCheck(user: User | null) {",
" if (typeof user === 'object') return user.email;",
"}",
"export function lateCheck(user: User | null) {",
" const email = user.email;",
" if (typeof user === 'string') return '';",
" return email;",
"}",
"interface User { email: string }",
}, "\n"))

report := runQualityPrecisionScan(t, qualityPrecisionConfigForLanguage(dir, "typescript"))

assertCodeQualityRulePresentForPathWithMessage(t, report, "defensive.null-assumption", "unsafe-typeof.ts:2")
assertCodeQualityRulePresentForPathWithMessage(t, report, "defensive.null-assumption", "unsafe-typeof.ts:5")
}

func TestDefensiveBoundaryInputSkipsTypedInternalDTOs(t *testing.T) {
dir := t.TempDir()
writeFile(t, filepath.Join(dir, "packages/api/src/routers/internal-dtos.ts"), strings.Join([]string{
Expand Down
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