From f4e66fe56f7bdeb8dfe6e2c5ebb5a1886aa96089 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 6 May 2026 23:15:11 +0000
Subject: [PATCH 1/3] Initial plan


From 0743417797da59fe91030bf82316b1b575ad674f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 7 May 2026 00:06:28 +0000
Subject: [PATCH 2/3] Add tests for inline if/unless with arg as condition [GH
 #21042]

Agent-Logs-Url: https://github.com/emberjs/ember.js/sessions/eeaec1fb-7e92-497a-9eae-adcc5fbc23b9

Co-authored-by: NullVoxPopuli <199018+NullVoxPopuli@users.noreply.github.com>
---
 .../integration-tests/test/updating-test.ts   | 92 +++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/packages/@glimmer-workspace/integration-tests/test/updating-test.ts b/packages/@glimmer-workspace/integration-tests/test/updating-test.ts
index 46f2c627834..2f4eda48a1e 100644
--- a/packages/@glimmer-workspace/integration-tests/test/updating-test.ts
+++ b/packages/@glimmer-workspace/integration-tests/test/updating-test.ts
@@ -792,6 +792,98 @@ class UpdatingTest extends RenderTest {
     this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
   }
 
+  @test
+  'if keyword in append position with arg as condition [GH emberjs/ember.js#21042]'() {
+    this.registerComponent('TemplateOnly', 'Foo', '{{if @condition "truthy"}}');
+    this.render('<Foo @condition={{this.condition}} />', {
+      condition: true,
+    });
+
+    this.assertHTML('truthy', 'Initial render');
+
+    this.rerender({ condition: false });
+    this.assertHTML('', 'If the condition is false nothing renders');
+
+    this.rerender({ condition: true });
+    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+  }
+
+  @test
+  'if keyword in append position with arg as condition with falsy [GH emberjs/ember.js#21042]'() {
+    this.registerComponent('TemplateOnly', 'Foo', '{{if @condition "truthy" "falsy"}}');
+    this.render('<Foo @condition={{this.condition}} />', {
+      condition: true,
+    });
+
+    this.assertHTML('truthy', 'Initial render');
+
+    this.rerender({ condition: false });
+    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+
+    this.rerender({ condition: true });
+    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+  }
+
+  @test
+  'unless keyword in append position with arg as condition [GH emberjs/ember.js#21042]'() {
+    this.registerComponent('TemplateOnly', 'Foo', '{{unless @condition "falsy"}}');
+    this.render('<Foo @condition={{this.condition}} />', {
+      condition: false,
+    });
+
+    this.assertHTML('falsy', 'Initial render');
+
+    this.rerender({ condition: true });
+    this.assertHTML('', 'If the condition is true nothing renders');
+
+    this.rerender({ condition: false });
+    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+  }
+
+  @test
+  'unless keyword in append position with arg as condition with truthy [GH emberjs/ember.js#21042]'() {
+    this.registerComponent('TemplateOnly', 'Foo', '{{unless @condition "falsy" "truthy"}}');
+    this.render('<Foo @condition={{this.condition}} />', {
+      condition: false,
+    });
+
+    this.assertHTML('falsy', 'Initial render');
+
+    this.rerender({ condition: true });
+    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+
+    this.rerender({ condition: false });
+    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+  }
+
+  @test
+  'if keyword in append position with @tracked arg as condition [GH emberjs/ember.js#21042]'() {
+    let parentInstance!: ParentComponent;
+
+    class ParentComponent extends GlimmerishComponent {
+      @tracked condition = true;
+
+      constructor(owner: object, args: Record<string, unknown>) {
+        super(owner, args);
+        parentInstance = this;
+      }
+    }
+
+    this.registerComponent('TemplateOnly', 'Foo', '{{if @condition "truthy" "falsy"}}');
+    this.registerComponent('Glimmer', 'Parent', '<Foo @condition={{this.condition}} />', ParentComponent);
+    this.render('<Parent />');
+
+    this.assertHTML('truthy', 'Initial render');
+
+    parentInstance.condition = false;
+    this.rerender();
+    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+
+    parentInstance.condition = true;
+    this.rerender();
+    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+  }
+
   @test
   'unless keyword in call position'() {
     this.registerComponent('TemplateOnly', 'Foo', '{{@value}}');

From 13ad9c6ed61a4f1a459f1095e32cf2a8b0f0b2ee Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 7 May 2026 07:14:36 +0000
Subject: [PATCH 3/3] Fix inline if/unless with component args: add
 VM_ASSERT_SAME_OP for component branch

Agent-Logs-Url: https://github.com/emberjs/ember.js/sessions/c9384514-8a79-4fd1-997c-859207137897

Co-authored-by: NullVoxPopuli <199018+NullVoxPopuli@users.noreply.github.com>
---
 .../integration-tests/test/updating-test.ts   | 109 ++++++++----------
 .../lib/opcode-builder/helpers/stdlib.ts      |   1 +
 2 files changed, 46 insertions(+), 64 deletions(-)

diff --git a/packages/@glimmer-workspace/integration-tests/test/updating-test.ts b/packages/@glimmer-workspace/integration-tests/test/updating-test.ts
index 2f4eda48a1e..3f6eeff4b83 100644
--- a/packages/@glimmer-workspace/integration-tests/test/updating-test.ts
+++ b/packages/@glimmer-workspace/integration-tests/test/updating-test.ts
@@ -7,6 +7,7 @@ import { createComputeRef, createConstRef, createPrimitiveRef } from '@glimmer/r
 import { consumeTag, createTag, dirtyTag } from '@glimmer/validator';
 import {
   assertNodeTagName,
+  defineComponent,
   getElementByClassName,
   getElementsByTagName,
   GlimmerishComponent,
@@ -15,6 +16,7 @@ import {
   stripTight,
   test,
   tracked,
+  trackedObj,
   trimLines,
 } from '@glimmer-workspace/integration-tests';
 
@@ -794,94 +796,73 @@ class UpdatingTest extends RenderTest {
 
   @test
   'if keyword in append position with arg as condition [GH emberjs/ember.js#21042]'() {
-    this.registerComponent('TemplateOnly', 'Foo', '{{if @condition "truthy"}}');
-    this.render('<Foo @condition={{this.condition}} />', {
-      condition: true,
-    });
+    const Ok = defineComponent({}, 'ok');
+    const Ko = defineComponent({}, 'ko');
+    const Flipper = defineComponent({ Ok, Ko }, '{{if @isOk Ok Ko}}');
 
-    this.assertHTML('truthy', 'Initial render');
+    let args = trackedObj({ isOk: true });
 
-    this.rerender({ condition: false });
-    this.assertHTML('', 'If the condition is false nothing renders');
-
-    this.rerender({ condition: true });
-    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
-  }
-
-  @test
-  'if keyword in append position with arg as condition with falsy [GH emberjs/ember.js#21042]'() {
-    this.registerComponent('TemplateOnly', 'Foo', '{{if @condition "truthy" "falsy"}}');
-    this.render('<Foo @condition={{this.condition}} />', {
-      condition: true,
-    });
+    this.renderComponent(Flipper, args);
+    this.assertHTML('ok', 'Initial render');
 
-    this.assertHTML('truthy', 'Initial render');
-
-    this.rerender({ condition: false });
-    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+    args['isOk'] = false;
+    this.rerender();
+    this.assertHTML('ko', 'If the condition is false, the falsy component renders');
 
-    this.rerender({ condition: true });
-    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+    args['isOk'] = true;
+    this.rerender();
+    this.assertHTML('ok', 'If the condition is true, the truthy component renders');
   }
 
   @test
   'unless keyword in append position with arg as condition [GH emberjs/ember.js#21042]'() {
-    this.registerComponent('TemplateOnly', 'Foo', '{{unless @condition "falsy"}}');
-    this.render('<Foo @condition={{this.condition}} />', {
-      condition: false,
-    });
-
-    this.assertHTML('falsy', 'Initial render');
+    const Ok = defineComponent({}, 'ok');
+    const Ko = defineComponent({}, 'ko');
+    const Flipper = defineComponent({ Ok, Ko }, '{{unless @isOk Ko Ok}}');
 
-    this.rerender({ condition: true });
-    this.assertHTML('', 'If the condition is true nothing renders');
+    let args = trackedObj({ isOk: false });
 
-    this.rerender({ condition: false });
-    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
-  }
+    this.renderComponent(Flipper, args);
+    this.assertHTML('ko', 'Initial render');
 
-  @test
-  'unless keyword in append position with arg as condition with truthy [GH emberjs/ember.js#21042]'() {
-    this.registerComponent('TemplateOnly', 'Foo', '{{unless @condition "falsy" "truthy"}}');
-    this.render('<Foo @condition={{this.condition}} />', {
-      condition: false,
-    });
-
-    this.assertHTML('falsy', 'Initial render');
-
-    this.rerender({ condition: true });
-    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+    args['isOk'] = true;
+    this.rerender();
+    this.assertHTML('ok', 'If the condition is true, the truthy component renders');
 
-    this.rerender({ condition: false });
-    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+    args['isOk'] = false;
+    this.rerender();
+    this.assertHTML('ko', 'If the condition is false, the falsy component renders');
   }
 
   @test
   'if keyword in append position with @tracked arg as condition [GH emberjs/ember.js#21042]'() {
-    let parentInstance!: ParentComponent;
+    const Ok = defineComponent({}, 'ok');
+    const Ko = defineComponent({}, 'ko');
+    const Flipper = defineComponent({ Ok, Ko }, '{{if @isOk Ok Ko}}');
 
-    class ParentComponent extends GlimmerishComponent {
-      @tracked condition = true;
+    let instance!: { isOk: boolean };
 
-      constructor(owner: object, args: Record<string, unknown>) {
-        super(owner, args);
-        parentInstance = this;
-      }
-    }
+    const Demo = defineComponent({ Flipper }, '<Flipper @isOk={{this.isOk}} />', {
+      definition: class extends GlimmerishComponent {
+        @tracked isOk = true;
 
-    this.registerComponent('TemplateOnly', 'Foo', '{{if @condition "truthy" "falsy"}}');
-    this.registerComponent('Glimmer', 'Parent', '<Foo @condition={{this.condition}} />', ParentComponent);
-    this.render('<Parent />');
+        constructor(owner: object, args: Record<string, unknown>) {
+          super(owner, args);
+          instance = this;
+        }
+      },
+    });
 
-    this.assertHTML('truthy', 'Initial render');
+    this.renderComponent(Demo);
+    this.assertHTML('ok', 'Initial render');
 
-    parentInstance.condition = false;
+    instance.isOk = false;
     this.rerender();
-    this.assertHTML('falsy', 'If the condition is false, the falsy value renders');
+    this.assertHTML('ko', 'If the condition is false, the falsy component renders');
 
-    parentInstance.condition = true;
+    instance.isOk = true;
     this.rerender();
-    this.assertHTML('truthy', 'If the condition is true, the truthy value renders');
+    this.assertHTML('ok', 'If the condition is true, the truthy component renders');
   }
 
   @test
diff --git a/packages/@glimmer/opcode-compiler/lib/opcode-builder/helpers/stdlib.ts b/packages/@glimmer/opcode-compiler/lib/opcode-builder/helpers/stdlib.ts
index 466add49cc9..4f4b29746ea 100644
--- a/packages/@glimmer/opcode-compiler/lib/opcode-builder/helpers/stdlib.ts
+++ b/packages/@glimmer/opcode-compiler/lib/opcode-builder/helpers/stdlib.ts
@@ -56,6 +56,7 @@ export function StdAppend(
 
       if (typeof nonDynamicAppend === 'number') {
         when(ContentType.Component, () => {
+          op(VM_ASSERT_SAME_OP);
           op(VM_RESOLVE_CURRIED_COMPONENT_OP);
           op(VM_PUSH_DYNAMIC_COMPONENT_INSTANCE_OP);
           InvokeBareComponent(op);