[export-defer] Add export defer namespace-object evaluation-triggers cases

Test the observable deferred evaluation semantics of `export defer`
namespace objects. The proposal only inserts EvaluateModuleSync into
[[Get]], so only operations that route through [[Get]] on the namespace
object trigger deferred source evaluation.

Tests use three template families that reflect this classification:

  trigger-on-exported/ (4 variants: string-exported, string-not-exported,
    then-exported, then-not-exported)
    For operations that route through [[Get]] and trigger evaluation when
    the key is a deferred-reexported name. The string-not-exported and
    then-not-exported variants verify that non-exported keys do NOT trigger
    (the [[Get]] returns undefined before reaching
    GetOptionalIndirectExportsModuleRequests).

  no-trigger-on-exported/ (4 variants: string-exported,
    string-not-exported, then-exported, then-not-exported)
    For key-sensitive operations that never route through [[Get]].

  no-trigger/ (1 variant: no key)
    For operations that take no property key or where the key is
    irrelevanr, ns evaluation is never triggered.

Author: caiolima

src/export-defer/defineOwnProperty.case

@@ -0,0 +1,20 @@
+// 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-defineownproperty-p-desc
+desc: _ [[DefineOwnProperty]]
+info: |
+  [[DefineOwnProperty]] ( _P_, _Desc_ )
+    1. If _P_ is a Symbol, return OrdinaryDefineOwnProperty(_O_, _P_, _Desc_).
+    1. Let _current_ be ? _O_.[[GetOwnProperty]](_P_).
+    1. If _current_ is *undefined*, return *false*.
+    1. ...
+
+template: trigger-on-exported
+---*/
+
+//- body
+try {
+  Object.defineProperty(ns, key, { value: "hi" });
+} catch (_) {}

src/export-defer/delete.case

@@ -0,0 +1,20 @@
+// 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-delete-p
+desc: _ [[Delete]]
+info: |
+  [[Delete]] ( _P_ )
+    1. If _P_ is a Symbol, return OrdinaryDelete(_O_, _P_).
+    1. Let _exports_ be _O_.[[Exports]].
+    1. If _exports_ contains _P_, return *false*.
+    1. Return *true*.
+
+template: no-trigger-on-exported
+---*/
+
+//- body
+try {
+  delete ns[key];
+} catch (_) {}

src/export-defer/get-in-prototype.case

@@ -0,0 +1,19 @@
+// 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
+desc: _ [[Get]] when namespace object is in the prototype chain
+info: |
+  [[Get]] ( _P_, _Receiver_ )
+    1. If _P_ is a Symbol, return OrdinaryGet(_O_, _P_, _Receiver_).
+    1. Let _exports_ be _O_.[[Exports]].
+    1. If _exports_ does not contain _P_, return *undefined*.
+    1. ...
+
+template: trigger-on-exported
+---*/
+
+//- body
+const obj = Object.create(ns);
+obj[key];

src/export-defer/get.case

@@ -0,0 +1,18 @@
+// 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
+desc: _ [[Get]]
+info: |
+  [[Get]] ( _P_, _Receiver_ )
+    1. If _P_ is a Symbol, return OrdinaryGet(_O_, _P_, _Receiver_).
+    1. Let _exports_ be _O_.[[Exports]].
+    1. If _exports_ does not contain _P_, return *undefined*.
+    1. ...
+
+template: trigger-on-exported
+---*/
+
+//- body
+ns[key];

src/export-defer/getOwnProperty.case

@@ -0,0 +1,19 @@
+// 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-getownproperty-p
+desc: _ [[GetOwnProperty]]
+info: |
+  [[GetOwnProperty]] ( _P_ )
+    1. If _P_ is a Symbol, return OrdinaryGetOwnProperty(_O_, _P_).
+    1. Let _exports_ be _O_.[[Exports]].
+    1. If _exports_ does not contain _P_, return *undefined*.
+    1. Let value be ? _O_.[[Get]](_P_, _O_).
+    1. Return PropertyDescriptor { [[Value]]: _value_, [[Writable]]: *true*, [[Enumerable]]: *true*, [[Configurable]]: *false* }.
+
+template: trigger-on-exported
+---*/
+
+//- body
+Object.getOwnPropertyDescriptor(ns, key);

src/export-defer/hasProperty-in-prototype.case

@@ -0,0 +1,19 @@
+// 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-hasproperty-p
+desc: _ [[HasProperty]] when namespace object is in the prototype chain
+info: |
+  [[HasProperty]] ( _P_ )
+    1. If _P_ is a Symbol, return OrdinaryHasProperty(_O_, _P_).
+    1. Let _exports_ be _O_.[[Exports]].
+    1. If _exports_ contains _P_, return *true*.
+    1. Return *false*.
+
+template: no-trigger-on-exported
+---*/
+
+//- body
+const obj = Object.create(ns);
+key in obj;

src/export-defer/hasProperty.case

@@ -0,0 +1,18 @@
+// 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-hasproperty-p
+desc: _ [[HasProperty]]
+info: |
+  [[HasProperty]] ( _P_ )
+    1. If _P_ is a Symbol, return OrdinaryHasProperty(_O_, _P_).
+    1. Let _exports_ be _O_.[[Exports]].
+    1. If _exports_ contains _P_, return *true*.
+    1. Return *false*.
+
+template: no-trigger-on-exported
+---*/
+
+//- body
+key in ns;

src/export-defer/no-trigger-on-exported/string-exported.template

@@ -0,0 +1,30 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/export/export-defer/evaluation-triggers/ignore-exported-string-
+name: of a string that is a deferred-reexported name, does not trigger evaluation
+esid: sec-module-namespace-exotic-objects
+info: |
+    EvaluateModuleSync is only inserted into [[Get]] by this proposal.
+    Operations that do not route through [[Get]] do not reach it,
+    even for a deferred-reexported name.
+
+flags: [module]
+features: [export-defer]
+includes: [compareArray.js]
+---*/
+
+import "./setup_FIXTURE.js";
+
+import * as ns from "./barrel_FIXTURE.js";
+
+assert.compareArray(globalThis.evaluations, ["barrel"],
+  "barrel evaluated eagerly; deferred source not yet evaluated");
+
+var key = "exported";
+
+/*{ body }*/
+
+assert.compareArray(globalThis.evaluations, ["barrel"],
+  "operation does not route through [[Get]], so deferred source is not evaluated");

src/export-defer/no-trigger-on-exported/string-not-exported.template

@@ -0,0 +1,30 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/export/export-defer/evaluation-triggers/ignore-not-exported-string-
+name: of a string that is not a deferred-reexported name, does not trigger evaluation
+esid: sec-module-namespace-exotic-objects
+info: |
+    EvaluateModuleSync is only inserted into [[Get]] by this proposal.
+    Operations that do not route through [[Get]] do not reach it,
+    even for a deferred-reexported name.
+
+flags: [module]
+features: [export-defer]
+includes: [compareArray.js]
+---*/
+
+import "./setup_FIXTURE.js";
+
+import * as ns from "./barrel_FIXTURE.js";
+
+assert.compareArray(globalThis.evaluations, ["barrel"],
+  "barrel evaluated eagerly; deferred source not yet evaluated");
+
+var key = "notExported";
+
+/*{ body }*/
+
+assert.compareArray(globalThis.evaluations, ["barrel"],
+  "operation does not route through [[Get]], so deferred source is not evaluated");

src/export-defer/no-trigger-on-exported/then-exported.template

@@ -0,0 +1,30 @@
+// Copyright (C) 2026 Igalia, S.L. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/export/export-defer/evaluation-triggers/ignore-exported-then-
+name: of "then" when it is a deferred-reexported name, does not trigger evaluation
+esid: sec-module-namespace-exotic-objects
+info: |
+    EvaluateModuleSync is only inserted into [[Get]] by this proposal.
+    Operations that do not route through [[Get]] do not reach it,
+    even for a deferred-reexported name.
+
+flags: [module]
+features: [export-defer]
+includes: [compareArray.js]
+---*/
+
+import "./setup_FIXTURE.js";
+
+import * as ns from "./barrel-then_FIXTURE.js";
+
+assert.compareArray(globalThis.evaluations, ["barrel"],
+  "barrel evaluated eagerly; deferred source not yet evaluated");
+
+var key = "then";
+
+/*{ body }*/
+
+assert.compareArray(globalThis.evaluations, ["barrel"],
+  "operation does not route through [[Get]], so deferred source is not evaluated");