Allow .mts and .mjs imports in no-asset-imports

scripts/project-lint.ts

@@ -70,14 +70,18 @@ const noDisableCommentsRule: ProjectRule = {
 /** A module specifier read as a path: relative, absolute, or a `#` alias. */
 const PATH_SPECIFIER_PATTERN: RegExp = /^[./#]/u;
 
-/** Script module extensions an import may name: our `.ts` files and `.js` package subpaths. */
-const SCRIPT_EXTENSIONS: readonly string[] = [".ts", ".js"];
+/**
+ * Script module extensions an import may name: our `.ts` files and `.js`,
+ * `.mts`, or `.mjs` package subpaths. `.cts`, `.cjs`, `.tsx`, and `.jsx` are
+ * not among them.
+ */
+const SCRIPT_EXTENSIONS: ReadonlySet<string> = new Set([".ts", ".js", ".mts", ".mjs"]);
 
 /**
  * Whether `source` names an asset rather than a script module: a query string
- * such as `?raw`, or a final path segment with an extension other than `.ts`
- * or `.js`. Bare package names are left alone, dots and all, as are
- * extensionless paths.
+ * such as `?raw`, or a final path segment whose extension, from its last dot,
+ * is not `.ts`, `.js`, `.mts`, or `.mjs`. Bare package names are left alone,
+ * dots and all, as are extensionless paths.
  */
 function isAssetSource(source: string): boolean {
   if (source.includes("?")) {
@@ -94,25 +98,28 @@ function isAssetSource(source: string): boolean {
   if (lastSegment === "." || lastSegment === ".." || !lastSegment.includes(".")) {
     return false;
   }
-  return !SCRIPT_EXTENSIONS.some((extension: string): boolean => lastSegment.endsWith(extension));
+  const extension: string = lastSegment.slice(lastSegment.lastIndexOf("."));
+  return !SCRIPT_EXTENSIONS.has(extension);
 }
 
 /**
  * `no-asset-imports` — rejects importing anything but a script module: a
  * source path, static or a dynamic `import()` with a string literal, ending in
- * an extension other than `.ts` or `.js` (`.css`, `.json`, `.svg`, `.tsx`) or
- * carrying a query string (`?raw`, `?url`), and any import or export with
- * import attributes. `.js` covers package subpaths such as
- * `lit/decorators.js`. Bare package names, `#` aliases, and `node:` builtins
+ * an extension other than `.ts`, `.js`, `.mts`, or `.mjs` (`.css`, `.json`,
+ * `.svg`, `.jsx`, `.tsx`, `.cjs`) or carrying a query string (`?raw`, `?url`),
+ * and any import or export with import attributes. `.js`, `.mts`, and `.mjs`
+ * cover package subpaths such as `lit/decorators.js` or
+ * `pdfjs-dist/legacy/build/pdf.mjs`; our own files are still `.ts` only. Bare
+ * package names, `#` aliases, and `node:` builtins
  * without an extension pass; package subpaths are checked like paths.
  */
 const noAssetImportsRule: ProjectRule = {
   meta: {
     type: "problem",
-    docs: { description: "Disallow importing assets instead of .ts or .js modules" },
+    docs: { description: "Disallow importing assets instead of .ts, .js, .mts, or .mjs modules" },
     schema: [],
     messages: {
-      extension: "Only .ts and .js modules may be imported.",
+      extension: "Only .ts, .js, .mts and .mjs modules may be imported.",
       attributes: "Import attributes are not allowed.",
     },
   },