Function isSealedModule

src/resolution/name-matcher.ts:1330–1357

* Whether `filePath` is a JS/TS module that exports NOTHING — an import * statement present, no export of any form. No reference from another file can * reach any binding in such a file, so every one of its symbols is a false * candidate for a cross-file name match. * * This is the general case

(filePath: string, context: ResolutionContext)

 *   equivalent boundary, and several extractors hardcode `isExported`.
 */
function isSealedModule(filePath: string, context: ResolutionContext): boolean {
  let memo = SEALED_MODULES.get(context);
  if (!memo) {
    memo = new Map();
    SEALED_MODULES.set(context, memo);
  }
  const hit = memo.get(filePath);
  if (hit !== undefined) return hit;
  // CommonJS assignments can execute inside template interpolations, which the
  // masker blanks. Keep the conservative raw-source exemption for those forms.
  // Cheapest disqualifiers first: nearly every module exports a node (asked
  // without reading or decoding the file), and masking the source is only
  // needed to rule out the ones that don't. (The masker only blanks text, so
  // no `import` in the source means none in code.)
  const exportsNode = context.fileHasExportedNode
    ? context.fileHasExportedNode(filePath)
    : context.getNodesInFile(filePath).some((n) => n.isExported);
  const source = exportsNode ? null : context.readFile(filePath);
  const sealed =
    !exportsNode && source !== null && source.includes('import') &&
    !HAS_CJS_EXPORT.test(source) &&
    (() => {
      const code = blankStringContents(stripCommentsForRegex(source, 'typescript'));
      return HAS_IMPORT_STATEMENT.test(code) && !HAS_ESM_EXPORT.test(code);
    })();
  memo.set(filePath, sealed);
  return sealed;
}

/**
 * Whether `candidate` can be named by a reference in `ref`'s file at all.