processFn() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Program.ts lines 584–704

function processFn(
  fn: BabelFn,
  fnType: ReactFunctionType,
  programContext: ProgramContext,
  outputMode: CompilerOutputMode,
): null | CodegenFunction {
  let directives: {
    optIn: t.Directive | null;
    optOut: t.Directive | null;
  };
  if (fn.node.body.type !== 'BlockStatement') {
    directives = {
      optIn: null,
      optOut: null,
    };
  } else {
    const optIn = tryFindDirectiveEnablingMemoization(
      fn.node.body.directives,
      programContext.opts,
    );
    if (optIn.isErr()) {
      /**
       * If parsing opt-in directive fails, it's most likely that React Compiler
       * was not tested or rolled out on this function. In that case, we handle
       * the error and fall back to the safest option which is to not optimize
       * the function.
       */
      handleError(optIn.unwrapErr(), programContext, fn.node.loc ?? null);
      return null;
    }
    directives = {
      optIn: optIn.unwrapOr(null),
      optOut: findDirectiveDisablingMemoization(
        fn.node.body.directives,
        programContext.opts,
      ),
    };
  }

  let compiledFn: CodegenFunction;
  const compileResult = tryCompileFunction(
    fn,
    fnType,
    programContext,
    outputMode,
  );
  if (compileResult.kind === 'error') {
    if (directives.optOut != null) {
      logError(compileResult.error, programContext, fn.node.loc ?? null);
    } else {
      handleError(compileResult.error, programContext, fn.node.loc ?? null);
    }
    if (outputMode === 'client') {
      const retryResult = retryCompileFunction(fn, fnType, programContext);
      if (retryResult == null) {
        return null;
      }
      compiledFn = retryResult;
    } else {
      return null;
    }
  } else {
    compiledFn = compileResult.compiledFn;
  }

  /**
   * If 'use no forget/memo' is present and we still ran the code through the
   * compiler for validation, log a skip event and don't mutate the babel AST.
   * This allows us to flag if there is an unused 'use no forget/memo'
   * directive.
   */
  if (
    programContext.opts.ignoreUseNoForget === false &&
    directives.optOut != null
  ) {
    programContext.logEvent({
      kind: 'CompileSkip',
      fnLoc: fn.node.body.loc ?? null,
      reason: `Skipped due to '${directives.optOut.value}' directive.`,
      loc: directives.optOut.loc ?? null,
    });