transformScope() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/PruneNonEscapingScopes.ts lines 1021–1060

  override transformScope(
    scopeBlock: ReactiveScopeBlock,
    state: Set<DeclarationId>,
  ): Transformed<ReactiveStatement> {
    this.visitScope(scopeBlock, state);

    /**
     * Scopes may initially appear "empty" because the value being memoized
     * is early-returned from within the scope. For now we intentionaly keep
     * these scopes, and let them get pruned later by PruneUnusedScopes
     * _after_ handling the early-return case in PropagateEarlyReturns.
     *
     * Also keep the scope if an early return was created by some earlier pass,
     * which may happen in alternate compiler configurations.
     */
    if (
      (scopeBlock.scope.declarations.size === 0 &&
        scopeBlock.scope.reassignments.size === 0) ||
      scopeBlock.scope.earlyReturnValue !== null
    ) {
      return {kind: 'keep'};
    }

    const hasMemoizedOutput =
      Array.from(scopeBlock.scope.declarations.values()).some(decl =>
        state.has(decl.identifier.declarationId),
      ) ||
      Array.from(scopeBlock.scope.reassignments).some(identifier =>
        state.has(identifier.declarationId),
      );
    if (hasMemoizedOutput) {
      return {kind: 'keep'};
    } else {
      this.prunedScopes.add(scopeBlock.scope.id);
      return {
        kind: 'replace-many',
        value: scopeBlock.instructions,
      };
    }
  }