dropManualMemoization() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/Inference/DropManualMemoization.ts lines 389–554

export function dropManualMemoization(
  func: HIRFunction,
): Result<void, CompilerError> {
  const errors = new CompilerError();
  const isValidationEnabled =
    func.env.config.validatePreserveExistingMemoizationGuarantees ||
    func.env.config.validateNoSetStateInRender ||
    func.env.config.enablePreserveExistingMemoizationGuarantees;
  const optionals = findOptionalPlaces(func);
  const sidemap: IdentifierSidemap = {
    functions: new Map(),
    manualMemos: new Map(),
    react: new Set(),
    maybeDeps: new Map(),
    maybeDepsLists: new Map(),
    optionals,
  };
  let nextManualMemoId = 0;

  /**
   * Phase 1:
   * - Overwrite manual memoization from
   *   CallExpression callee="useMemo/Callback", args=[fnArg, depslist])
   *   to either
   *   CallExpression callee=fnArg
   *   LoadLocal fnArg
   * - (if validation is enabled) collect manual memoization markers
   */
  const queuedInserts: Map<
    InstructionId,
    TInstruction<StartMemoize> | TInstruction<FinishMemoize>
  > = new Map();
  for (const [_, block] of func.body.blocks) {
    for (let i = 0; i < block.instructions.length; i++) {
      const instr = block.instructions[i]!;
      if (
        instr.value.kind === 'CallExpression' ||
        instr.value.kind === 'MethodCall'
      ) {
        const id =
          instr.value.kind === 'CallExpression'
            ? instr.value.callee.identifier.id
            : instr.value.property.identifier.id;

        const manualMemo = sidemap.manualMemos.get(id);
        if (manualMemo != null) {
          const memoDetails = extractManualMemoizationArgs(
            instr as TInstruction<CallExpression> | TInstruction<MethodCall>,
            manualMemo.kind,
            sidemap,
            errors,
          );

          if (memoDetails == null) {
            continue;
          }
          const {fnPlace, depsList, depsLoc} = memoDetails;

          instr.value = getManualMemoizationReplacement(
            fnPlace,
            instr.value.loc,
            manualMemo.kind,
          );
          if (isValidationEnabled) {
            /**
             * Explicitly bail out when we encounter manual memoization
             * without inline instructions, as our current validation
             * assumes that source depslists closely match inferred deps
             * due to the `exhaustive-deps` lint rule (which only provides
             * diagnostics for inline memo functions)
             * ```js
             * useMemo(opaqueFn, [dep1, dep2]);
             * ```
             * While we could handle this by diffing reactive scope deps
             * of the opaque arg against the source depslist, this pattern
             * is rare and likely sketchy.
             */
            if (!sidemap.functions.has(fnPlace.identifier.id)) {
              errors.pushDiagnostic(
                CompilerDiagnostic.create({
                  category: ErrorCategory.UseMemo,