chore: update lint rules

web/eslint-plugins/conventions/no-string-union-alias.js

@@ -0,0 +1,64 @@
+// Rule: NO STRING-LITERAL UNION TYPE ALIASES.
+//
+// A type alias whose members are all string literals (`type Kind = 'a' | 'b'`)
+// duplicates the literal set: the same set is re-typed in many places, and new
+// "derived" aliases (`type Kind2 = 'a' | 'c'`) appear that drift from the
+// source. Prefer a single `as const` object as the source of truth and derive
+// the type from it with indexed access.
+//
+//     const KIND = { a: ..., b: ..., c: ... } as const;
+//     type Kind = (typeof KIND)[keyof typeof KIND];
+//
+// Only TSTypeAliasDeclaration is checked — inline unions in parameter or
+// property types (one-off uses) are left alone.
+
+/** True when the union and all its (possibly nested) members are string literals. */
+function allStringLiterals(/** @type {any} */ union) {
+	for (const member of union.types) {
+		if (member.type === "TSUnionType") {
+			if (!allStringLiterals(member)) return false;
+		} else if (member.type === "TSLiteralType") {
+			const literal = member.literal;
+			if (!(literal.type === "Literal" && typeof literal.value === "string")) {
+				return false;
+			}
+		} else {
+			return false;
+		}
+	}
+	return true;
+}
+
+export default {
+	meta: {
+		type: "suggestion",
+		docs: {
+			description:
+				"Ban string-literal union type aliases in favor of an `as const` object plus `(typeof X)[keyof typeof X]`.",
+			category: "TypeScript conventions",
+			recommended: true,
+		},
+		schema: [],
+		messages: {
+			stringUnion:
+				"Prefer one `as const` object over the string-literal union alias '{{name}}' — literal sets duplicated across types or files drift apart. Derive the type instead: `const {{constName}} = {...} as const; type {{name}} = (typeof {{constName}})[keyof typeof {{constName}}]`.",
+		},
+	},
+	create(context) {
+		return {
+			TSTypeAliasDeclaration(node) {
+				const annotation = node.typeAnnotation;
+				if (!annotation || annotation.type !== "TSUnionType") return;
+				if (!allStringLiterals(annotation)) return;
+				context.report({
+					node: node.id,
+					messageId: "stringUnion",
+					data: {
+						name: node.id.name,
+						constName: node.id.name.toUpperCase(),
+					},
+				});
+			},
+		};
+	},
+};