ask262/engine262/src/abstract-ops/module-records.mts

import {
  surroundingAgent, HostLoadImportedModule, HostPromiseRejectionTracker,
} from '../host-defined/engine.mts';
import { IncrementModuleAsyncEvaluationCount } from '../execution-context/Agent.mts';
import {
  CyclicModuleRecord,
  SyntheticModuleRecord,
  ResolvedBindingRecord,
  AbstractModuleRecord,
  type ModuleRecordHostDefined,
  ModuleRecord,
} from '../modules.mts';
import {
  JSStringValue, ObjectValue, Value,
} from '../value.mts';
import {
  Q, X, NormalCompletion, ThrowCompletion, AbruptCompletion,
  type PlainCompletion,
  EnsureCompletion,
} from '../completion.mjs';
import {
  Assert,
  ModuleNamespaceCreate,
  NewPromiseCapability,
  PerformPromiseThen,
  CreateBuiltinFunction,
  Call,
  ContinueDynamicImport,
  PromiseCapabilityRecord,
} from './all.mts';
import {
  Realm,
  Completion,
  HostGetSupportedImportAttributes,
  ModuleRequestsEqual,
  ReadyForSyncExecution,
  type Arguments, type ImportAttributeRecord, type ModuleRequestRecord, type PlainEvaluator, type ScriptRecord, type SourceTextModuleRecord,
} from '#self';

/** https://tc39.es/ecma262/#graphloadingstate-record */
export class GraphLoadingState {
  readonly PromiseCapability: PromiseCapabilityRecord;

  readonly HostDefined?: ModuleRecordHostDefined;

  IsLoading = true;

  readonly Visited = new Set<CyclicModuleRecord>();

  PendingModules = 1;

  constructor({ PromiseCapability, HostDefined }: Pick<GraphLoadingState, 'PromiseCapability' | 'HostDefined'>) {
    this.PromiseCapability = PromiseCapability;
    this.HostDefined = HostDefined;
  }
}

/** https://tc39.es/ecma262/#sec-InnerModuleLoading */
export function InnerModuleLoading(state: GraphLoadingState, module: AbstractModuleRecord) {
  // 1. Assert: state.[[IsLoading]] is true.
  Assert(Boolean(state.IsLoading === true)); // this Boolean() is let step 2.d.iii not having a type error.

  // 2. If module is a Cyclic Module Record, module.[[Status]] is new, and state.[[Visited]] does not contain module, then
  if (module instanceof CyclicModuleRecord && module.Status === 'new' && !state.Visited.has(module)) {
    // a. Append module to state.[[Visited]].
    state.Visited.add(module);
    // b. Let requestedModulesCount be the number of elements in module.[[RequestedModules]].
    const requestedModulesCout = module.RequestedModules.length;
    // c. Set state.[[PendingModulesCount]] to state.[[PendingModulesCount]] + requestedModulesCount.
    state.PendingModules += requestedModulesCout;
    // d. For each ModuleRequest Record request of module.[[RequestedModules]], do
    for (const request of module.RequestedModules) {
      // i. If AllImportAttributesSupported(request.[[Attributes]]) is false, then
      const invalidAttributeKey = AllImportAttributesSupported(request.Attributes);
      if (invalidAttributeKey) {
        // 1. Let error be ThrowCompletion(a newly created SyntaxError object).
        const error = surroundingAgent.Throw('SyntaxError', 'UnsupportedImportAttribute', invalidAttributeKey);
        // 2. Perform ContinueModuleLoading(state, error).
        ContinueModuleLoading(state, error);
      } else {
        // ii. Else if module.[[LoadedModules]] contains a LoadedModuleRequest Record record such that ModuleRequestsEqual(record, request) is true, then
        const record = getRecordWithSpecifier(module.LoadedModules, request);
        if (record !== undefined) {
          // 1. Perform InnerModuleLoading(state, record.[[Module]]).
          InnerModuleLoading(state, record.Module);
        } else { // iii. Else,
          // 1. Perform HostLoadImportedModule(module, request, state.[[HostDefined]], state).
          HostLoadImportedModule(module, request, state.HostDefined, state);
        }
      }

      // iii. If state.[[IsLoading]] is false, return unused.
      if (state.IsLoading === false) {
        return;
      }
    }
  }

  // 3. Assert: state.[[PendingModulesCount]] ≥ 1.
  Assert(state.PendingModules >= 1);
  // 4. Set state.[[PendingModulesCount]] to state.[[PendingModulesCount]] - 1.
  state.PendingModules -= 1;
  // 5. If state.[[PendingModulesCount]] = 0, then
  if (state.PendingModules === 0) {
    // a. Set state.[[IsLoading]] to false.
    state.IsLoading = false;
    // b. For each Cyclic Module Record loaded of state.[[Visited]], do
    for (const loaded of state.Visited) {
      // i. If loaded.[[Status]] is new, set loaded.[[Status]] to unlinked.
      if (loaded.Status === 'new') {
        loaded.Status = 'unlinked';
      }
    }
    // c. Perform ! Call(state.[[PromiseCapability]].[[Resolve]], undefined, « undefined »).
    X(Call(state.PromiseCapability.Resolve, Value.undefined, [Value.undefined]));
  }

  // 6. Return unused.
}

/** https://tc39.es/ecma262/#sec-ContinueModuleLoading */
export function ContinueModuleLoading(state: GraphLoadingState, result: PlainCompletion<AbstractModuleRecord>) {
  // 1. If state.[[IsLoading]] is false, return unused.
  if (state.IsLoading === false) {
    return;
  }
  result = EnsureCompletion(result);
  // 2. If moduleCompletion is a normal completion, then
  if (result instanceof NormalCompletion) {
    // a. Perform InnerModuleLoading(state, moduleCompletion.[[Value]]).
    InnerModuleLoading(state, result.Value);
    // 3. Else,
  } else {
    // a. Set state.[[IsLoading]] to false.
    state.IsLoading = false;
    // b. Perform ! Call(state.[[PromiseCapability]].[[Reject]], undefined, « moduleCompletion.[[Value]] »).
    X(Call(state.PromiseCapability.Reject, Value.undefined, [result.Value]));
  }

  // 4. Return unused.
}

/** https://tc39.es/ecma262/#sec-InnerModuleLinking */
export function InnerModuleLinking(module: AbstractModuleRecord, stack: CyclicModuleRecord[], index: number): PlainCompletion<number> {
  if (!(module instanceof CyclicModuleRecord)) {
    Q(module.Link());
    return index;
  }
  if (module.Status === 'linking' || module.Status === 'linked' || module.Status === 'evaluating-async' || module.Status === 'evaluated') {
    return index;
  }
  Assert(module.Status === 'unlinked');
  module.Status = 'linking';
  const moduleIndex = index;
  module.DFSAncestorIndex = index;
  index += 1;
  stack.push(module);
  for (const required of module.RequestedModules) {
    const requiredModule = GetImportedModule(module, required);
    index = Q(InnerModuleLinking(requiredModule, stack, index));
    if (requiredModule instanceof CyclicModuleRecord) {
      Assert(requiredModule.Status === 'linking' || requiredModule.Status === 'linked' || requiredModule.Status === 'evaluating-async' || requiredModule.Status === 'evaluated');
      Assert((requiredModule.Status === 'linking') === stack.includes(requiredModule));
      if (requiredModule.Status === 'linking') {
        module.DFSAncestorIndex = Math.min(module.DFSAncestorIndex, requiredModule.DFSAncestorIndex!);
      }
    }
  }
  Q((module as SourceTextModuleRecord).InitializeEnvironment());
  Assert(stack.indexOf(module) === stack.lastIndexOf(module));
  Assert(module.DFSAncestorIndex <= moduleIndex);
  if (module.DFSAncestorIndex === moduleIndex) {
    let done = false;
    while (done === false) {
      const requiredModule = stack.pop();
      Assert(requiredModule instanceof CyclicModuleRecord);
      requiredModule.Status = 'linked';
      if (requiredModule === module) {
        done = true;
      }
    }
  }
  return index;
}

/** https://tc39.es/ecma262/#sec-EvaluateModuleSync */
export function* EvaluateModuleSync(module: ModuleRecord): PlainEvaluator<undefined> {
  // 1. Assert: If module is a Cyclic Module Record, ReadyForSyncExecution(module) is true.
  Assert(module instanceof CyclicModuleRecord ? ReadyForSyncExecution(module) === Value.true : true);
  // 2. Let promise be module.Evaluate()./
  const promise = yield* module.Evaluate();
  // 3. Assert: promise.[[PromiseState]] is either fulfilled or rejected.
  Assert(promise.PromiseState === 'fulfilled' || promise.PromiseState === 'rejected');
  // 4. If promise.[[PromiseState]] is rejected, then
  if (promise.PromiseState === 'rejected') {
    // a. If promise.[[PromiseIsHandled]] is false, perform HostPromiseRejectionTracker(promise, "handle").
    if (promise.PromiseIsHandled === Value.false) {
      HostPromiseRejectionTracker(promise, 'handle');
    }
    // b. Set promise.[[PromiseIsHandled]] to true.
    promise.PromiseIsHandled = Value.true;
    // c. Return ThrowCompletion(promise.[[PromiseResult]]).
    return ThrowCompletion(promise.PromiseResult!);
  }
  // 5. Return unused.
  return undefined;
}

/** https://tc39.es/ecma262/#sec-innermoduleevaluation */
export function* InnerModuleEvaluation(module: AbstractModuleRecord, stack: CyclicModuleRecord[], index: number): PlainEvaluator<number> {
  if (!(module instanceof CyclicModuleRecord)) {
    Q(yield* EvaluateModuleSync(module));
    return NormalCompletion(index);
  }
  if (module.Status === 'evaluating-async' || module.Status === 'evaluated') {
    if (module.EvaluationError === undefined) {
      return NormalCompletion(index);
    } else {
      return module.EvaluationError;
    }
  }
  if (module.Status === 'evaluating') {
    return NormalCompletion(index);
  }
  Assert(module.Status === 'linked');
  module.Status = 'evaluating';
  const moduleIndex = index;
  module.DFSAncestorIndex = index;
  module.PendingAsyncDependencies = 0;
  module.AsyncParentModules = [];
  index += 1;
  const evaluationList: ModuleRecord[] = [];
  for (const request of module.RequestedModules) {
    const requiredModule = GetImportedModule(module, request);
    if (request.Phase === 'defer') {
      const additionalModules = GatherAsynchronousTransitiveDependencies(requiredModule);
      for (const additionalModule of additionalModules) {
        if (!evaluationList.includes(additionalModule)) {
          evaluationList.push(additionalModule);
        }
      }
    } else if (!evaluationList.includes(requiredModule)) {
      evaluationList.push(requiredModule);
    }
  }
  stack.push(module);
  for (const required of evaluationList!) {
    let requiredModule: ModuleRecord | CyclicModuleRecord = required as ModuleRecord;
    index = Q(yield* InnerModuleEvaluation(requiredModule, stack, index));
    if (requiredModule instanceof CyclicModuleRecord) {
      Assert(requiredModule.Status === 'evaluating' || requiredModule.Status === 'evaluating-async' || requiredModule.Status === 'evaluated');
      Assert((requiredModule.Status === 'evaluating') === stack.includes(requiredModule));
      if (requiredModule.Status === 'evaluating') {
        module.DFSAncestorIndex = Math.min(module.DFSAncestorIndex, requiredModule.DFSAncestorIndex!);
      } else {
        requiredModule = requiredModule.CycleRoot!;
        Assert((requiredModule as CyclicModuleRecord).Status === 'evaluating-async' || (requiredModule as CyclicModuleRecord).Status === 'evaluated');
        if ((requiredModule as CyclicModuleRecord).EvaluationError !== undefined) {
          return EnsureCompletion((requiredModule as CyclicModuleRecord).EvaluationError);
        }
      }
      if (typeof (requiredModule as CyclicModuleRecord).AsyncEvaluationOrder === 'number') {
        module.PendingAsyncDependencies += 1;
        (requiredModule as CyclicModuleRecord).AsyncParentModules.push(module);
      }
    }
  }
  if (module.PendingAsyncDependencies > 0 || module.HasTLA === Value.true) {
    Assert(module.AsyncEvaluationOrder === 'unset');
    module.AsyncEvaluationOrder = IncrementModuleAsyncEvaluationCount();
    if (module.PendingAsyncDependencies === 0) {
      X(yield* ExecuteAsyncModule(module));
    }
  } else {
    Q(yield* module.ExecuteModule());
  }
  Assert(stack.indexOf(module) === stack.lastIndexOf(module));
  Assert(module.DFSAncestorIndex <= moduleIndex);
  if (module.DFSAncestorIndex === moduleIndex) {
    let done = false;
    while (done === false) {
      const requiredModule = stack.pop();
      Assert(requiredModule instanceof CyclicModuleRecord);
      Assert(typeof requiredModule.AsyncEvaluationOrder === 'number' || requiredModule.AsyncEvaluationOrder === 'unset');
      if (requiredModule.AsyncEvaluationOrder === 'unset') {
        requiredModule.Status = 'evaluated';
      } else {
        requiredModule.Status = 'evaluating-async';
      }
      if (requiredModule === module) {
        done = true;
      }
      requiredModule.CycleRoot = module;
    }
  }
  return index;
}

/** https://tc39.es/proposal-defer-import-eval/#sec-GatherAsynchronousTransitiveDependencies  */
export function GatherAsynchronousTransitiveDependencies(module: ModuleRecord, seen?: Set<ModuleRecord>): ModuleRecord[] {
  // 1. If seen is not present, set seen to a new empty List.
  seen ??= new Set();
  // 2. Let result be a new empty List.
  const result: ModuleRecord[] = [];
  // 3. If seen contains module, return result.
  if (seen.has(module)) {
    return result;
  }
  // 4. Append module to seen.
  seen.add(module);
  // 5. If module is not a Cyclic Module Record, return result.
  if (!(module instanceof CyclicModuleRecord)) {
    return result;
  }
  // 6. If module.[[Status]] is either evaluating or evaluated, return result.
  if (module.Status === 'evaluating' || module.Status === 'evaluated') {
    return result;
  }
  // 7. If module.[[HasTLA]] is true, then
  if (module.HasTLA === Value.true) {
    // a. Append module to result.
    result.push(module);
    // b. Return result.
    return result;
  }
  // 8. For each ModuleRequest Record request of module.[[RequestedModules]], do
  for (const request of module.RequestedModules) {
    // a. Let requiredModule be GetImportedModule(module, request).
    const requiredModule = GetImportedModule(module, request);
    // b. Let additionalModules be GatherAsynchronousTransitiveDependencies(requiredModule, seen).
    const additionalModules = GatherAsynchronousTransitiveDependencies(requiredModule, seen);
    // c. For each Module Record m of additionalModules, do
    for (const m of additionalModules) {
      // i. If result does not contain m, append m to result.
      if (!result.includes(m)) {
        result.push(m);
      }
    }
  }
  // 9. Return result.
  return result;
}

/** https://tc39.es/ecma262/#sec-execute-async-module */
function* ExecuteAsyncModule(module: CyclicModuleRecord) {
  // 1. Assert: module.[[Status]] is evaluating or evaluating-async.
  Assert(module.Status === 'evaluating' || module.Status === 'evaluating-async');
  // 2. Assert: module.[[HasTLA]] is true.
  Assert(module.HasTLA === Value.true);
  // 3. Let capability be ! NewPromiseCapability(%Promise%).
  const capability = X(NewPromiseCapability(surroundingAgent.intrinsic('%Promise%')));
  // 4. Let fulfilledClosure be a new Abstract Closure with no parameters that captures module and performs the following steps when called:
  function* fulfilledClosure() {
    // a. Perform ! AsyncModuleExecutionFulfilled(module).
    X(yield* AsyncModuleExecutionFulfilled(module));
    // b. Return undefined.
    return Value.undefined;
  }
  // 5. Let onFulfilled be ! CreateBuiltinFunction(fulfilledClosure, 0, "", « »).
  const onFulfilled = CreateBuiltinFunction(fulfilledClosure, 0, Value(''), ['Module']);
  // 6. Let rejectedClosure be a new Abstract Closure with parameters (error) that captures module and performs the following steps when called:
  const rejectedClosure = ([error = Value.undefined]: Arguments) => {
    // a. Perform ! AsyncModuleExecutionRejected(module, error).
    X(AsyncModuleExecutionRejected(module, error));
    // b. Return undefined.
    return Value.undefined;
  };
  // 7. Let onRejected be ! CreateBuiltinFunction(rejectedClosure, 0, "", « »).
  const onRejected = CreateBuiltinFunction(rejectedClosure, 0, Value(''), ['Module']);
  // 8. Perform ! PerformPromiseThen(capability.[[Promise]], onFulfilled, onRejected).
  X(PerformPromiseThen(capability.Promise, onFulfilled, onRejected));
  // 9. Perform ! module.ExecuteModule(capability).
  X(yield* module.ExecuteModule(capability));
  // 10. Return.
  return Value.undefined;
}

/** https://tc39.es/ecma262/#sec-gather-available-ancestors */
function GatherAvailableAncestors(module: CyclicModuleRecord, execList: CyclicModuleRecord[]) {
  for (const m of module.AsyncParentModules) {
    if (!execList.includes(m) && m.CycleRoot!.EvaluationError === undefined) {
      Assert(m.Status === 'evaluating-async');
      Assert(m.EvaluationError === undefined);
      Assert(typeof m.AsyncEvaluationOrder === 'number');
      Assert(m.PendingAsyncDependencies! > 0);
      m.PendingAsyncDependencies! -= 1;
      if (m.PendingAsyncDependencies === 0) {
        execList.push(m);
        if (m.HasTLA === Value.false) {
          GatherAvailableAncestors(m, execList);
        }
      }
    }
  }
}

/** https://tc39.es/ecma262/#sec-asyncmodulexecutionfulfilled */
function* AsyncModuleExecutionFulfilled(module: CyclicModuleRecord): PlainEvaluator {
  if (module.Status === 'evaluated') {
    Assert(module.EvaluationError !== undefined);
    return;
  }
  Assert(module.Status === 'evaluating-async');
  Assert(typeof module.AsyncEvaluationOrder === 'number');
  Assert(module.EvaluationError === undefined);
  module.AsyncEvaluationOrder = 'done';
  module.Status = 'evaluated';
  if (module.TopLevelCapability !== undefined) {
    Assert(module.CycleRoot === module);
    X(Call(module.TopLevelCapability.Resolve, Value.undefined, [Value.undefined]));
  }

  const execList: CyclicModuleRecord[] = [];
  GatherAvailableAncestors(module, execList);
  Assert(execList.every((m) => typeof m.AsyncEvaluationOrder === 'number' && m.PendingAsyncDependencies === 0 && m.EvaluationError === undefined));
  const sortedExecList = execList.toSorted((m1, m2) => (m1.AsyncEvaluationOrder as number) - (m2.AsyncEvaluationOrder as number));

  for (const m of sortedExecList) {
    if (m.Status === 'evaluated') {
      Assert(m.EvaluationError !== undefined);
    } else if (m.HasTLA === Value.true) {
      X(yield* ExecuteAsyncModule(m));
    } else {
      const result = yield* m.ExecuteModule();
      if (result instanceof AbruptCompletion) {
        X(AsyncModuleExecutionRejected(m, result.Value));
      } else {
        m.AsyncEvaluationOrder = 'done';
        m.Status = 'evaluated';
        if (m.TopLevelCapability !== undefined) {
          Assert(m.CycleRoot === m);
          X(Call(m.TopLevelCapability.Resolve, Value.undefined, [Value.undefined]));
        }
      }
    }
  }
}

/** https://tc39.es/ecma262/#sec-AsyncModuleExecutionRejected */
function AsyncModuleExecutionRejected(module: CyclicModuleRecord, error: Value) {
  if (module.Status === 'evaluated') {
    Assert(module.EvaluationError !== undefined);
    return;
  }
  Assert(module.Status === 'evaluating-async');
  Assert(typeof module.AsyncEvaluationOrder === 'number');
  Assert(module.EvaluationError === undefined);
  module.EvaluationError = ThrowCompletion(error);
  module.Status = 'evaluated';
  module.AsyncEvaluationOrder = 'done';
  if (module.TopLevelCapability !== undefined) {
    Assert(module.CycleRoot === module);
    X(Call(module.TopLevelCapability.Reject, Value.undefined, [error]));
  }
  for (const m of module.AsyncParentModules) {
    AsyncModuleExecutionRejected(m, error);
  }
}

function getRecordWithSpecifier(loadedModules: CyclicModuleRecord['LoadedModules'], request: ModuleRequestRecord) {
  const records = loadedModules.filter((r) => ModuleRequestsEqual(r, request));
  Assert(records.length <= 1);
  return records.length === 1 ? records[0] : undefined;
}

/** https://tc39.es/ecma262/#sec-GetImportedModule */
export function GetImportedModule(referrer: CyclicModuleRecord, request: ModuleRequestRecord) {
  const record = getRecordWithSpecifier(referrer.LoadedModules, request);
  Assert(record !== undefined);
  return record.Module;
}

/** https://tc39.es/ecma262/#sec-FinishLoadingImportedModule */
export function FinishLoadingImportedModule(referrer: ScriptRecord | CyclicModuleRecord | Realm, moduleRequest: ModuleRequestRecord, result: PlainCompletion<AbstractModuleRecord>, state: GraphLoadingState | PromiseCapabilityRecord) {
  result = EnsureCompletion(result);
  // 1. If result is a normal completion, then
  if (result.Type === 'normal') {
    // a. If referrer.[[LoadedModules]] contains a LoadedModuleRequest Record record such that ModuleRequestsEqual(record, moduleRequest) is true, then
    const record = getRecordWithSpecifier(referrer.LoadedModules, moduleRequest);
    if (record !== undefined) {
      // i. Assert: That Record's [[Module]] is result.[[Value]].
      Assert(record.Module === result.Value);
    } else { // b. Else,
      //  i. Append the LoadedModuleRequest Record { [[Specifier]]: moduleRequest.[[Specifier]], [[Attributes]]: moduleRequest.[[Attributes]], [[Module]]: result.[[Value]] } to referrer.[[LoadedModules]].
      referrer.LoadedModules.push({ Specifier: moduleRequest.Specifier, Attributes: moduleRequest.Attributes, Module: result.Value });
    }
  }

  // 2. If payload is a GraphLoadingState Record, then
  if (state instanceof GraphLoadingState) {
    // a. Perform ContinueModuleLoading(payload, result).
    ContinueModuleLoading(state, result);
    // 3. Else,
  } else {
    // a. Perform ContinueDynamicImport(payload, result).
    ContinueDynamicImport(state, result, moduleRequest.Phase);
  }

  // 4. Return unused.
}

/** https://tc39.es/ecma262/#sec-AllImportAttributesSupported */
export function AllImportAttributesSupported(attributes: readonly ImportAttributeRecord[]) {
  // Note: This function is meant to return a boolean. Instead, we return:
  // - instead of *false*, the key of the unsupported attribute
  // - instead of *true*, undefined

  const supported: readonly string[] = HostGetSupportedImportAttributes();
  for (const attribute of attributes) {
    if (!supported.includes(attribute.Key.stringValue())) {
      return attribute.Key;
    }
  }
  return undefined;
}

/** https://tc39.es/ecma262/#sec-getmodulenamespace */
export function GetModuleNamespace(
  module: AbstractModuleRecord,
  phase: 'defer' | 'evaluation',
): ObjectValue {
  // 1. Assert: If module is a Cyclic Module Record, then module.[[Status]] is not new or unlinked.
  if (module instanceof CyclicModuleRecord) {
    Assert(module.Status !== 'new' && module.Status !== 'unlinked');
  }
  // 2. Let namespace be module.[[Namespace]].
  let namespace = phase === 'defer' ? module.DeferredNamespace : module.Namespace;
  // 3. If namespace is empty, then
  if (namespace === undefined) {
    // a. Let exportedNames be module.GetExportedNames().
    const exportedNames = module.GetExportedNames();
    // b. Let unambiguousNames be a new empty List.
    const unambiguousNames = [];
    // c. For each element name of exportedNames, do
    for (const name of exportedNames) {
      // i. Let resolution be module.ResolveExport(name).
      const resolution = module.ResolveExport(name);
      // ii. If resolution is a ResolvedBinding Record, append name to unambiguousNames.
      if (resolution instanceof ResolvedBindingRecord) {
        unambiguousNames.push(name);
      }
    }
    // d. Set namespace to ModuleNamespaceCreate(module, unambiguousNames).
    namespace = ModuleNamespaceCreate(module, unambiguousNames, phase);
  }
  // 4. Return namespace.
  return namespace;
}

export function CreateSyntheticModule(exportNames: readonly JSStringValue[], evaluationSteps: (record: SyntheticModuleRecord) => PlainEvaluator | Completion<unknown>, realm: Realm, hostDefined: ModuleRecordHostDefined) {
  // 1. Return Synthetic Module Record {
  //      [[Realm]]: realm,
  //      [[Environment]]: undefined,
  //      [[Namespace]]: undefined,
  //      [[HostDefined]]: hostDefined,
  //      [[ExportNames]]: exportNames,
  //      [[EvaluationSteps]]: evaluationSteps
  //    }.
  return new SyntheticModuleRecord({
    Realm: realm,
    Environment: undefined,
    Namespace: undefined,
    HostDefined: hostDefined,
    ExportNames: exportNames,
    EvaluationSteps: evaluationSteps,
  });
}

/** https://tc39.es/ecma262/#sec-create-default-export-synthetic-module */
export function CreateDefaultExportSyntheticModule(defaultExport: Value, realm: Realm, hostDefined: ModuleRecordHostDefined) {
  // 1. Let closure be the a Abstract Closure with parameters (module) that captures defaultExport and performs the following steps when called:
  const closure = function* closure(module: SyntheticModuleRecord): PlainEvaluator {
    // a. Return module.SetSyntheticExport("default", defaultExport).
    Q(yield* module.SetSyntheticExport(Value('default'), defaultExport));
    return NormalCompletion(undefined);
  };
  // 2. Return CreateSyntheticModule(« "default" », closure, realm)
  return CreateSyntheticModule([Value('default')], closure, realm, hostDefined);
}