Function rewriteImports

packages/unpkg-worker/src/lib/pkg-imports.ts:6–42

(code: string, origin: string, dependencies: Record<string, string>)

 * Rewrites all imports in the given code to point to unpkg URLs.
 */
export function rewriteImports(code: string, origin: string, dependencies: Record<string, string>): string {
  let [imports] = parse(code);
  let rewrites: { start: number; end: number; value: string }[] = [];

  for (let imp of imports) {
    // Skip imports without a specifier
    if (imp.n === undefined) {
      continue;
    }

    let specifier = code.slice(imp.s, imp.e);

    let rewriteValue: string;
    if (imp.t === 2) {
      // dynamic import()
      let match = /^(["'])([^"']*)\1$/.exec(specifier);
      if (match === null) continue; // not a simple string literal
      rewriteValue = match[1] + rewriteSpecifier(match[2], origin, dependencies) + match[1];
    } else {
      rewriteValue = rewriteSpecifier(specifier, origin, dependencies);
    }

    if (rewriteValue !== specifier) {
      rewrites.push({ start: imp.s, end: imp.e, value: rewriteValue });
    }
  }

  // Sort rewrites in reverse order to avoid position shifts
  rewrites.sort((a, b) => b.start - a.start);

  let result = code;
  for (let { start, end, value } of rewrites) {
    result = result.slice(0, start) + value + result.slice(end);
  }

  return result;
}

function rewriteSpecifier(specifier: string, origin: string, dependencies: Record<string, string>): string {
  if (specifier === "" || isValidUrl(specifier)) {