Refuse a declaring module's mergeable file that names no keys (hq issue 574, ADR 0326 §3)

A module that declares a setting and owns a mergeable file naming no keys
still let every key reach that file. The refusal was held back in #272
because betterbird was one; mesh-catalog #252 named its keys, and every
module in mesh-catalog and mesh-media-catalog main now passes, so the
module check and registration refuse it again. A stored definition is
still composed as it is, never left out of a machine.

internal/catalogue/setting_takes.go

@@ -70,10 +70,23 @@ func namesItsKeys(m Manifest) bool {
 // reads itself, one the file keeps for itself, or one mergeable file naming its keys beside another
 // that names none.
 func TakenSettingsProblems(m Manifest) []string {
-	// Not yet here: refusing a module that declares a setting and owns a mergeable file naming no keys
-	// (ADR 0326 §3). betterbird is one, and the catalogue cannot name its keys before this controller
-	// runs, so that refusal follows once the catalogue does (novox/hq issue 574).
-	return takenSettingsProblems(m)
+	problems := takenSettingsProblems(m)
+	// **A module that declares a setting names the keys of every mergeable file** (ADR 0326 §3, ADR
+	// 0164 §11 and §15; novox/hq issue 574): only a module that declares none keeps today's form. Said
+	// where a definition is checked and registered, never where a stored one is composed: a definition
+	// stored before this rule is brought into the form by its next change, not left out of a machine
+	// meanwhile.
+	if len(m.Settings) > 0 {
+		for _, r := range m.Resources {
+			how, _ := r["merge"].(string)
+			if _, said := r[TakesSettingsField]; how != "" && !said {
+				problems = append(problems, fmt.Sprintf("%s declares settings, and its mergeable %v names no %s: "+
+					"a module that declares a setting names the keys each mergeable file takes, an empty list "+
+					"for none (novox/hq ADR 0326 §3, ADR 0164 §11)", m.Module, r["id"], TakesSettingsField))
+			}
+		}
+	}
+	return problems
 }
 
 // takenSettingsProblems is every rule of ADR 0326 §2 and §4, judged where a definition is checked and

internal/catalogue/setting_takes_test.go

@@ -194,3 +194,29 @@ func containsText(list []string, text string) bool {
 	}
 	return false
 }
+
+func TestAModuleThatDeclaresASettingNamesItsFilesKeys(t *testing.T) {
+	// ADR 0326 §3, ADR 0164 §15, novox/hq issue 574: only a module that declares no settings keeps
+	// today's form. One that declares a preference and owns a silent mergeable file is refused where it
+	// is checked — and not where a stored definition is composed, so a machine does not lose it before
+	// its next change.
+	m := twoFiles(nil, nil)
+	m.Settings = map[string]SettingDeclaration{"site-name": {Kind: KindPreference, Default: "Search", Why: "a name"}}
+	problems := TakenSettingsProblems(m)
+	if len(problems) != 2 || !containsText(problems, "app names no takes-settings") ||
+		!containsText(problems, "sidecar names no takes-settings") {
+		t.Errorf("problems: %v", problems)
+	}
+	if err := JudgeSettings(m, nil, false); err != nil {
+		t.Errorf("a stored definition is composed as before, and was refused: %v", err)
+	}
+	m = twoFiles([]any{"server"}, []any{})
+	m.Settings = map[string]SettingDeclaration{"site-name": {Kind: KindPreference, Default: "Search", Why: "a name"}}
+	if problems := TakenSettingsProblems(m); len(problems) != 0 {
+		t.Errorf("every mergeable file names its keys, and was refused: %v", problems)
+	}
+	// And a module that declares none keeps today's form, silent files and all.
+	if problems := TakenSettingsProblems(twoFiles(nil, nil)); len(problems) != 0 {
+		t.Errorf("a module declaring no setting was refused: %v", problems)
+	}
+}