chore: update lint rules

web/eslint-plugins/__tests__/no-string-union-alias.test.ts

@@ -0,0 +1,78 @@
+// Tests for the conventions/no-string-union-alias rule
+// (web/eslint-plugins/conventions/no-string-union-alias.js).
+//
+// The rule is a pure AST check (no filesystem), so it runs through the standard
+// RuleTester: plain .ts via the tseslint parser, and (because the rule is also
+// enabled on new .svelte scripts) .svelte via the svelte tester. No fixtures.
+import { RuleTester } from "eslint";
+import svelteParser from "svelte-eslint-parser";
+import tseslint from "typescript-eslint";
+import { describe, it } from "vitest";
+import noStringUnionAlias from "../conventions/no-string-union-alias.js";
+import { asRuleModule, svelteComponent } from "./helpers.js";
+
+RuleTester.describe = describe;
+RuleTester.it = it;
+
+const tsTester = new RuleTester({
+	languageOptions: {
+		parser: tseslint.parser,
+	},
+});
+
+const svelteTester = new RuleTester({
+	languageOptions: {
+		parser: svelteParser,
+		parserOptions: { parser: tseslint.parser },
+	},
+});
+
+const frame = (script: string) => ({
+	code: svelteComponent(script),
+	filename: "Component.svelte",
+});
+
+tsTester.run("no-string-union-alias", asRuleModule(noStringUnionAlias), {
+	valid: [
+		{ code: "type X = 1 | 2;", filename: "types.ts" },
+		{ code: "type X = 'a' | number;", filename: "types.ts" },
+		{ code: "type X = string;", filename: "types.ts" },
+		{ code: "const KIND = { a: 1, b: 2 } as const;", filename: "types.ts" },
+		{ code: "function f(x: 'a' | 'b') {}", filename: "types.ts" },
+		{ code: "const x: 'a' | 'b' = 'a';", filename: "types.ts" },
+		{ code: "type X = 'a' | TemplateStrings;", filename: "types.ts" },
+	],
+	invalid: [
+		{
+			code: "type Kind = 'a' | 'b' | 'c';",
+			filename: "types.ts",
+			errors: [{ messageId: "stringUnion" }],
+		},
+		{
+			// Nested/parenthesized unions still resolve to string literals.
+			code: "type Kind = ('a' | 'b') | 'c';",
+			filename: "types.ts",
+			errors: [{ messageId: "stringUnion" }],
+		},
+		{
+			code: "type Lang =\n\t'en'\n\t| 'ru';",
+			filename: "types.ts",
+			errors: [{ messageId: "stringUnion" }],
+		},
+	],
+});
+
+// The rule also runs on new .svelte files (their scripts are TS).
+svelteTester.run(
+	"no-string-union-alias (svelte script)",
+	asRuleModule(noStringUnionAlias),
+	{
+		valid: [frame("type X = 1 | 2;"), frame("const M = { a: 1 } as const;")],
+		invalid: [
+			{
+				...frame("type Kind = 'a' | 'b' | 'c';"),
+				errors: [{ messageId: "stringUnion" }],
+			},
+		],
+	},
+);