collectScopeInfo() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/HIR/MergeOverlappingReactiveScopesHIR.ts lines 149–198

function collectScopeInfo(fn: HIRFunction): ScopeInfo {
  const scopeStarts: Map<InstructionId, Set<ReactiveScope>> = new Map();
  const scopeEnds: Map<InstructionId, Set<ReactiveScope>> = new Map();
  const placeScopes: Map<Place, ReactiveScope> = new Map();

  function collectPlaceScope(place: Place): void {
    const scope = place.identifier.scope;
    if (scope != null) {
      placeScopes.set(place, scope);
      /**
       * Record both mutating and non-mutating scopes to merge scopes with
       * still-mutating values with inner scopes that alias those values
       * (see `nonmutating-capture-in-unsplittable-memo-block`)
       *
       * Note that this isn't perfect, as it also leads to merging of mutating
       * scopes with JSX single-instruction scopes (see `mutation-within-jsx`)
       */
      if (scope.range.start !== scope.range.end) {
        getOrInsertDefault(scopeStarts, scope.range.start, new Set()).add(
          scope,
        );
        getOrInsertDefault(scopeEnds, scope.range.end, new Set()).add(scope);
      }
    }
  }

  for (const [, block] of fn.body.blocks) {
    for (const instr of block.instructions) {
      for (const operand of eachInstructionLValue(instr)) {
        collectPlaceScope(operand);
      }
      for (const operand of eachInstructionOperand(instr)) {
        collectPlaceScope(operand);
      }
    }
    for (const operand of eachTerminalOperand(block.terminal)) {
      collectPlaceScope(operand);
    }
  }

  return {
    scopeStarts: [...scopeStarts.entries()]
      .map(([id, scopes]) => ({id, scopes}))
      .sort((a, b) => b.id - a.id),
    scopeEnds: [...scopeEnds.entries()]
      .map(([id, scopes]) => ({id, scopes}))
      .sort((a, b) => b.id - a.id),
    placeScopes,
  };
}