transformDestructuring() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/ReactiveScopes/ExtractScopeDeclarationsFromDestructuring.ts lines 154–208

function transformDestructuring(
  state: State,
  instr: ReactiveInstruction,
  destructure: Destructure,
): null | Array<ReactiveInstruction> {
  let reassigned: Set<IdentifierId> = new Set();
  let hasDeclaration = false;
  for (const place of eachPatternOperand(destructure.lvalue.pattern)) {
    const isDeclared = state.declared.has(place.identifier.declarationId);
    if (isDeclared) {
      reassigned.add(place.identifier.id);
    } else {
      hasDeclaration = true;
    }
  }
  if (!hasDeclaration) {
    // all reassignments
    destructure.lvalue.kind = InstructionKind.Reassign;
    return null;
  }
  /*
   * Else it's a mix, replace the reassigned items in the destructuring with temporary
   * variables and emit separate assignment statements for them
   */
  const instructions: Array<ReactiveInstruction> = [];
  const renamed: Map<Place, Place> = new Map();
  mapPatternOperands(destructure.lvalue.pattern, place => {
    if (!reassigned.has(place.identifier.id)) {
      return place;
    }
    const temporary = clonePlaceToTemporary(state.env, place);
    promoteTemporary(temporary.identifier);
    renamed.set(place, temporary);
    return temporary;
  });
  instructions.push(instr);
  for (const [original, temporary] of renamed) {
    instructions.push({
      id: instr.id,
      lvalue: null,
      value: {
        kind: 'StoreLocal',
        lvalue: {
          kind: InstructionKind.Reassign,
          place: original,
        },
        value: temporary,
        type: null,
        loc: destructure.loc,
      },
      loc: instr.loc,
    });
  }
  return instructions;
}