getFunctionReferencedBeforeDeclarationAtTopLevel() — react Function Reference

Source Code

compiler/packages/babel-plugin-react-compiler/src/Entrypoint/Program.ts lines 1366–1425

function getFunctionReferencedBeforeDeclarationAtTopLevel(
  program: NodePath<t.Program>,
  fns: Array<CompileResult>,
): Set<CompileResult> {
  const fnNames = new Map<string, {id: t.Identifier; fn: CompileResult}>(
    fns
      .map<[NodePath<t.Expression> | null, CompileResult]>(fn => [
        getFunctionName(fn.originalFn),
        fn,
      ])
      .filter(
        (entry): entry is [NodePath<t.Identifier>, CompileResult] =>
          !!entry[0] && entry[0].isIdentifier(),
      )
      .map(entry => [entry[0].node.name, {id: entry[0].node, fn: entry[1]}]),
  );
  const referencedBeforeDeclaration = new Set<CompileResult>();

  program.traverse({
    TypeAnnotation(path) {
      path.skip();
    },
    TSTypeAnnotation(path) {
      path.skip();
    },
    TypeAlias(path) {
      path.skip();
    },
    TSTypeAliasDeclaration(path) {
      path.skip();
    },
    Identifier(id) {
      const fn = fnNames.get(id.node.name);
      // We're not tracking this identifier.
      if (!fn) {
        return;
      }

      /*
       * We've reached the declaration, hoisting is no longer possible, stop
       * checking for this component name.
       */
      if (id.node === fn.id) {
        fnNames.delete(id.node.name);
        return;
      }

      const scope = id.scope.getFunctionParent();
      /*
       * A null scope means there's no function scope, which means we're at the
       * top level scope.
       */
      if (scope === null && id.isReferencedIdentifier()) {
        referencedBeforeDeclaration.add(fn.fn);
      }
    },
  });

  return referencedBeforeDeclaration;
}