[export-defer] Add tests for error propagation

test/language/export/export-defer/load-and-evaluation/circular-references/consumer-cycle/barrel_FIXTURE.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+export defer { x } from "./entry_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/circular-references/consumer-cycle/consumer-cycle.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-resolveexport
+description: A deferred re-export forming a cycle with its consumer throws SyntaxError at link time
+info: |
+  ResolveExport ( exportName [ , resolveSet [ , deferNamespaceExportSet ] ] )
+    1. Assert: module.[[Status]] is not NEW.
+    1. If resolveSet is not present, set resolveSet to a new empty List.
+    1. If deferNamespaceExportSet is not present, set deferNamespaceExportSet to a new empty List.
+    1. For each Record { [[Module]], [[ExportName]] } r of resolveSet, do
+       1. If module and r.[[Module]] are the same Module Record and exportName is r.[[ExportName]], then
+          1. Assert: This is a circular import request.
+          1. Return null.
+    1. ...
+
+  Like we have for ordinary re-exports, circular deferred re-exports also throws SyntaxError.
+flags: [module, async]
+features: [export-defer, dynamic-import]
+includes: [asyncHelpers.js]
+---*/
+
+asyncTest(async () => {
+  let err;
+  await import("./entry_FIXTURE.js").catch((e) => { err = e; });
+  assert.sameValue(err instanceof SyntaxError, true, "consumer-cycle throws SyntaxError");
+});

test/language/export/export-defer/load-and-evaluation/circular-references/consumer-cycle/entry_FIXTURE.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+import { x } from "./barrel_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/circular-references/cycle-imported/a_FIXTURE.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+globalThis.evaluations.push("a");
+export defer { x } from "./b_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/circular-references/cycle-imported/b_FIXTURE.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+globalThis.evaluations.push("b");
+export defer { x } from "./a_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/circular-references/cycle-imported/consumer_FIXTURE.js

@@ -0,0 +1,4 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+import { x } from "./a_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/circular-references/cycle-imported/cycle-imported-throws.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-resolveexport
+description: Cyclic deferred re-exports of the same binding throw SyntaxError when the binding is imported
+info: |
+  ResolveExport ( exportName [ , resolveSet [ , deferNamespaceExportSet ] ] )
+    1. Assert: module.[[Status]] is not NEW.
+    1. If resolveSet is not present, set resolveSet to a new empty List.
+    1. If deferNamespaceExportSet is not present, set deferNamespaceExportSet to a new empty List.
+    1. For each Record { [[Module]], [[ExportName]] } r of resolveSet, do
+       1. If module and r.[[Module]] are the same Module Record and exportName is r.[[ExportName]], then
+          1. Assert: This is a circular import request.
+          1. Return null.
+    1. ...
+flags: [module, async]
+features: [export-defer, dynamic-import]
+includes: [asyncHelpers.js]
+---*/
+
+asyncTest(async () => {
+  let err;
+  await import("./consumer_FIXTURE.js").catch((e) => { err = e; });
+  assert.sameValue(err instanceof SyntaxError, true, "cyclic deferred re-exports throw SyntaxError when imported");
+});

test/language/export/export-defer/load-and-evaluation/circular-references/cycle-imported/cycle-not-imported-no-throw.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-resolveexport
+description: Cyclic deferred re-exports do not throw SyntaxError if the cyclic binding is never imported
+info: |
+  InnerModuleLoading ( state, module, importedNames )
+    1. Assert: state.[[IsLoading]] is true.
+    1. If module is a Cyclic Module Record, then
+      1. ...
+      1. Let optionalIndirectRequests be GetNewOptionalIndirectExportsModuleRequests(module, importedNames, state.[[Visited]]).
+      1. Set requestsToLoad to the list-concatenation of requestsToLoad and optionalIndirectRequests.
+      1. ...
+
+  ResolveExport ( exportName [ , resolveSet [ , deferNamespaceExportSet ] ] )
+    1. Assert: module.[[Status]] is not NEW.
+    1. If resolveSet is not present, set resolveSet to a new empty List.
+    1. If deferNamespaceExportSet is not present, set deferNamespaceExportSet to a new empty List.
+    1. For each Record { [[Module]], [[ExportName]] } r of resolveSet, do
+       1. If module and r.[[Module]] are the same Module Record and exportName is r.[[ExportName]], then
+          1. Assert: This is a circular import request.
+          1. Return null.
+    1. ...
+
+    Not imported names aren't loaded, so their cycle nevergets visited and resolved.
+flags: [module]
+features: [export-defer]
+includes: [compareArray.js]
+---*/
+
+import "../setup_FIXTURE.js";
+import "./a_FIXTURE.js";
+
+assert.compareArray(
+  globalThis.evaluations,
+  ["a"],
+  "a evaluated; b's cycle never forced because no consumer requested x"
+);

test/language/export/export-defer/load-and-evaluation/circular-references/setup_FIXTURE.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+globalThis.evaluations = [];

test/language/export/export-defer/load-and-evaluation/runtime-errors/barrel-defer-throws_FIXTURE.js

@@ -0,0 +1,5 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+globalThis.evaluations.push("barrel-defer-throws");
+export defer { x } from "./throws_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/runtime-errors/namespace-access-throws-repeated.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-module-namespace-exotic-objects-get-p-receiver-EnsureDeferredNamespaceEvaluation
+description: Namespace [[Get]] of a deferred re-export with an erroring source throws on first access and on every subsequent access with the same error value
+info: |
+  [[Get]] ( P, Receiver )
+    1. ...
+    1. If m is a Cyclic Module Record and m.GetOptionalIndirectExportsModuleRequests(« P ») is not empty, then
+      1. Perform ? EvaluateModuleSync(m, « P »).
+    1. ...
+
+  EvaluateModuleSync ( module [ , importedNames ] )
+    1. ...
+    1. Let promise be module.Evaluate(importedNames).
+    1. Assert: promise.[[PromiseState]] is either FULFILLED or REJECTED.
+    1. If promise.[[PromiseState]] is REJECTED, then
+       1. If promise.[[PromiseIsHandled]] is false, perform HostPromiseRejectionTracker(promise, "handle").
+       1. Set promise.[[PromiseIsHandled]] to true.
+       1. Return ThrowCompletion(promise.[[PromiseResult]]).
+    1. ...
+
+  Evaluate ( [ importedNames ] )
+    1. ...
+    1. If module.[[Status]] is either EVALUATING-ASYNC or EVALUATED, then
+      1. Assert: module.[[CycleRoot]].[[TopLevelCapability]] is not EMPTY.
+      1. Let topLevelPromise be module.[[CycleRoot]].[[TopLevelCapability]].[[Promise]].
+    1. ...
+    1. If topLevelPromise.[[PromiseState]] is rejected, return topLevelPromise.
+
+flags: [module, async]
+features: [export-defer, dynamic-import]
+includes: [asyncHelpers.js]
+---*/
+
+import "./setup_FIXTURE.js";
+
+asyncTest(async () => {
+  let err1;
+  try { await import("./barrel-defer-throws_FIXTURE.js"); } catch (e) { err1 = e; }
+  assert.sameValue(err1.someError, "the error from throws_FIXTURE");
+
+  let err2;
+  try { await import("./barrel-defer-throws_FIXTURE.js"); } catch (e) { err2 = e; }
+  assert.sameValue(err2, err1, "subsequent accesses throw the same error value");
+});

test/language/export/export-defer/load-and-evaluation/runtime-errors/never-imported.js

@@ -0,0 +1,38 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-module-namespace-exotic-objects-get-p-receiver-EnsureDeferredNamespaceEvaluation
+description: A deferred re-export source that throws on evaluation does not throw if its binding is never accessed
+info: |
+  InnerModuleLoading ( state, module, importedNames )
+    1. Assert: state.[[IsLoading]] is true.
+    1. If module is a Cyclic Module Record, then
+      1. ...
+      1. Let optionalIndirectRequests be GetNewOptionalIndirectExportsModuleRequests(module, importedNames, state.[[Visited]]).
+      1. Set requestsToLoad to the list-concatenation of requestsToLoad and optionalIndirectRequests.
+      1. ...
+
+  ResolveExport ( exportName [ , resolveSet [ , deferNamespaceExportSet ] ] )
+    1. Assert: module.[[Status]] is not NEW.
+    1. If resolveSet is not present, set resolveSet to a new empty List.
+    1. If deferNamespaceExportSet is not present, set deferNamespaceExportSet to a new empty List.
+    1. For each Record { [[Module]], [[ExportName]] } r of resolveSet, do
+       1. If module and r.[[Module]] are the same Module Record and exportName is r.[[ExportName]], then
+          1. Assert: This is a circular import request.
+          1. Return null.
+    1. ...
+
+flags: [module]
+features: [export-defer]
+includes: [compareArray.js]
+---*/
+
+import "./setup_FIXTURE.js";
+import "./barrel-defer-throws_FIXTURE.js";
+
+assert.compareArray(
+  globalThis.evaluations,
+  ["barrel-defer-throws"],
+  "barrel evaluated; throws_FIXTURE was loaded but never evaluated"
+);

test/language/export/export-defer/load-and-evaluation/runtime-errors/reexport1_FIXTURE.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+export defer { x } from "./throws_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/runtime-errors/reexport2_FIXTURE.js

@@ -0,0 +1,4 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+export defer { x } from "./throws_FIXTURE.js";

test/language/export/export-defer/load-and-evaluation/runtime-errors/setup_FIXTURE.js

@@ -0,0 +1,4 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+globalThis.evaluations = [];

test/language/export/export-defer/load-and-evaluation/runtime-errors/throws_FIXTURE.js

@@ -0,0 +1,6 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+globalThis.evaluations.push("throws");
+throw { someError: "the error from throws_FIXTURE" };
+export const x = "never-reached";

test/language/export/export-defer/load-and-evaluation/runtime-errors/two-namespaces-same-error.js

@@ -0,0 +1,47 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-EvaluateModuleSync
+description: Two distinct deferred re-exports of x from the same throwing source surface the same error value through both namespaces
+info: |
+  [[Get]] ( P, Receiver )
+    1. ...
+    1. If m is a Cyclic Module Record and m.GetOptionalIndirectExportsModuleRequests(« P ») is not empty, then
+      1. Perform ? EvaluateModuleSync(m, « P »).
+    1. ...
+
+  EvaluateModuleSync ( module [ , importedNames ] )
+    1. ...
+    1. Let promise be module.Evaluate(importedNames).
+    1. Assert: promise.[[PromiseState]] is either FULFILLED or REJECTED.
+    1. If promise.[[PromiseState]] is REJECTED, then
+       1. If promise.[[PromiseIsHandled]] is false, perform HostPromiseRejectionTracker(promise, "handle").
+       1. Set promise.[[PromiseIsHandled]] to true.
+       1. Return ThrowCompletion(promise.[[PromiseResult]]).
+    1. ...
+
+  Evaluate ( [ importedNames ] )
+    1. ...
+    1. If module.[[Status]] is either EVALUATING-ASYNC or EVALUATED, then
+      1. Assert: module.[[CycleRoot]].[[TopLevelCapability]] is not EMPTY.
+      1. Let topLevelPromise be module.[[CycleRoot]].[[TopLevelCapability]].[[Promise]].
+    1. ...
+    1. If topLevelPromise.[[PromiseState]] is rejected, return topLevelPromise.
+
+flags: [module, async]
+features: [export-defer, dynamic-import]
+includes: [asyncHelpers.js]
+---*/
+
+import "./setup_FIXTURE.js";
+
+asyncTest(async () => {
+  let err1;
+  try { await import("./reexport1_FIXTURE.js"); } catch (e) { err1 = e; }
+  let err2;
+  try { await import("./reexport2_FIXTURE.js"); } catch (e) { err2 = e; }
+
+  assert.sameValue(err1.someError, "the error from throws_FIXTURE");
+  assert.sameValue(err1, err2, "both namespaces yield the same error value (identity)");
+});

test/language/export/export-defer/load-and-evaluation/runtime-errors/used-throws.js

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+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-EvaluateModuleSync
+description: When a deferred re-export binding is statically imported and read, the source's runtime error propagates to the consumer
+info: |
+  EvaluateModuleSync ( module [ , importedNames ] )
+    1. ...
+    1. Let promise be module.Evaluate(importedNames).
+    1. Assert: promise.[[PromiseState]] is either FULFILLED or REJECTED.
+    1. If promise.[[PromiseState]] is REJECTED, then
+       1. If promise.[[PromiseIsHandled]] is false, perform HostPromiseRejectionTracker(promise, "handle").
+       1. Set promise.[[PromiseIsHandled]] to true.
+       1. Return ThrowCompletion(promise.[[PromiseResult]]).
+    1. ...
+
+  Evaluate ( [ importedNames ] )
+    1. ...
+    1. For each ModuleRequest Record request of optionalIndirectRequests, do
+      1. Let requiredModule be GetImportedModule(module, request).
+      1. Assert: requiredModule.[[Status]] is one of LINKED, EVALUATING-ASYNC, or EVALUATED.
+      1. Let innerPromise be requiredModule.Evaluate(request.[[ImportedNames]]).
+      1. If innerPromise.[[PromiseState]] is REJECTED, return innerPromise.
+      1. Append innerPromise to promises.
+    1. ...
+
+flags: [module, async]
+features: [export-defer, dynamic-import]
+includes: [asyncHelpers.js]
+---*/
+
+import "./setup_FIXTURE.js";
+
+asyncTest(async () => {
+  let err;
+  await import("./uses-x_FIXTURE.js").catch((e) => { err = e; });
+  assert.sameValue(
+    err.someError,
+    "the error from throws_FIXTURE",
+    "evaluation error from deferred source propagates"
+  );
+});

test/language/export/export-defer/load-and-evaluation/runtime-errors/uses-x_FIXTURE.js

@@ -0,0 +1,4 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+import { x } from "./barrel-defer-throws_FIXTURE.js";