Skip _test.go files when parsing enum constants

docs/backlog/build-ignore-file-mixes-packages.md

@@ -0,0 +1,15 @@
+---
+worth: maybe
+where: internal/generator/generator.go:Parse
+added: 2026-10-31
+---
+# build-ignored file of another package makes the package clause random
+
+`Parse` reads every non-test `.go` file in the directory without evaluating build constraints, groups
+them by package and keeps whichever package the map visits last. A `//go:build ignore` helper of
+`package main` next to the enum (a common pattern for generator scripts) gives the generated file
+`package main` in some runs: 2 of 6 in a probe after the `_test.go` skip landed.
+
+Two shapes are open: honour build constraints (`go/build` or `build.Default.MatchFile`), or pick the
+package the enum type is declared in instead of the last one seen. Surfaced reviewing
+https://github.com/go-pkgz/enum/discussions/11.

docs/backlog/readme-test-files-ignored.md

@@ -0,0 +1,11 @@
+---
+worth: later
+where: README.md
+added: 2026-10-31
+---
+# README does not say _test.go files are ignored
+
+`Parse` skips `_test.go` files, so enum constants declared in tests are never collected. The README
+describes which constants are picked up but says nothing about test files, so someone declaring an
+enum in a test file gets "no const values found" with no hint why. One line in the constants section
+covers it.

internal/generator/generator.go

@@ -107,7 +107,8 @@ func (g *Generator) Parse(dir string) error {
 	// group parsed files by package name; mirrors the behaviour of the deprecated parser.ParseDir
 	pkgFiles := map[string][]*ast.File{}
 	for _, entry := range entries {
-		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".go") {
+		// the generated file is not a test file, so it can't reference anything declared in tests
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".go") || strings.HasSuffix(entry.Name(), "_test.go") {
 			continue
 		}
 		file, err := parser.ParseFile(fset, filepath.Join(dir, entry.Name()), nil, parser.ParseComments)

internal/generator/generator_test.go

@@ -372,6 +372,30 @@ func TestGenerator(t *testing.T) {
 	})
 }
 
+func TestParseSkipsTestFiles(t *testing.T) {
+	// regression: a black-box test package next to the enum made the package clause random
+	tmpDir := t.TempDir()
+	files := map[string]string{
+		"status.go":               "package p1\ntype status int\nconst (\n\tstatusUnknown status = iota\n\tstatusActive\n)\n",
+		"status_internal_test.go": "package p1\nconst statusFromInternalTest status = 10\n",
+		"status_external_test.go": "package p1_test\nconst statusFromExternalTest = 20\n",
+	}
+	for name, body := range files {
+		require.NoError(t, os.WriteFile(filepath.Join(tmpDir, name), []byte(body), 0o600))
+	}
+
+	gen, err := New("status", tmpDir)
+	require.NoError(t, err)
+	require.NoError(t, gen.Parse(tmpDir))
+
+	assert.Equal(t, "p1", gen.pkgName)
+	values := map[string]int64{}
+	for name := range gen.values {
+		values[name] = constVal(t, gen, name)
+	}
+	assert.Equal(t, map[string]int64{"statusUnknown": 0, "statusActive": 1}, values)
+}
+
 func TestGeneratorValues(t *testing.T) {
 	tmpDir := t.TempDir()
 
@@ -665,7 +689,7 @@ const (
 
 func TestNoLinterWarningsForUnusedConstants(t *testing.T) {
 	tmpDir := t.TempDir()
-	err := os.WriteFile(filepath.Join(tmpDir, "linter_test.go"), []byte(`
+	err := os.WriteFile(filepath.Join(tmpDir, "linter.go"), []byte(`
 package test
 type linterTest uint8
 const (