Function compileHmrInitializer

packages/compiler/src/render3/r3_hmr_compiler.ts:55–160

(meta: R3HmrMetadata)

 * @param meta HMR metadata extracted from the class.
 */
export function compileHmrInitializer(meta: R3HmrMetadata): o.Expression {
  const moduleName = 'm';
  const dataName = 'd';
  const timestampName = 't';
  const idName = 'id';
  const importCallbackName = `${meta.className}_HmrLoad`;
  const namespaces = meta.namespaceDependencies.map((dep) => {
    return new o.ExternalExpr({moduleName: dep.moduleName, name: null});
  });

  // m.default
  const defaultRead = o.variable(moduleName).prop('default');

  // ɵɵreplaceMetadata(Comp, m.default, [...namespaces], [...locals], import.meta, id);
  const replaceCall = o
    .importExpr(R3.replaceMetadata)
    .callFn([
      meta.type,
      defaultRead,
      o.literalArr(namespaces),
      o.literalArr(meta.localDependencies.map((l) => l.runtimeRepresentation)),
      o.variable('import').prop('meta'),
      o.variable(idName),
    ]);

  // (m) => m.default && ɵɵreplaceMetadata(...)
  const replaceCallback = o.arrowFn(
    [new o.FnParam(moduleName, o.DYNAMIC_TYPE)],
    defaultRead.and(replaceCall),
  );

  // getReplaceMetadataURL(id, timestamp, import.meta.url)
  const url = o
    .importExpr(R3.getReplaceMetadataURL)
    .callFn([
      o.variable(idName),
      o.variable(timestampName),
      o.variable('import').prop('meta').prop('url'),
    ]);

  // function Cmp_HmrLoad(t) {
  //   import(/* @vite-ignore */ url).then((m) => m.default && replaceMetadata(...));
  // }
  const importCallback = new o.DeclareFunctionStmt(
    importCallbackName,
    [new o.FnParam(timestampName, o.DYNAMIC_TYPE)],
    [
      // The vite-ignore special comment is required to prevent Vite from generating a superfluous
      // warning for each usage within the development code. If Vite provides a method to
      // programmatically avoid this warning in the future, this added comment can be removed here.
      new o.DynamicImportExpr(url, null, '@vite-ignore')
        .prop('then')
        .callFn([replaceCallback])
        .toStmt(),
    ],
    null,
    o.StmtModifier.Final,
  );