From a7862cf4032cc9b52aa2ff35fb1979c53331fba2 Mon Sep 17 00:00:00 2001
From: Ella-AWS <111664173+EllaCoat@users.noreply.github.com>
Date: Sun, 23 Aug 2026 04:50:12 +0000
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Blueprint=20=E3=81=AE=E5=AD=A4?=
 =?UTF-8?q?=E7=AB=8B=20Bone=20=E3=81=AB=E3=82=88=E3=82=8B=E5=90=8D?=
 =?UTF-8?q?=E5=89=8D=E8=A1=9D=E7=AA=81=E3=82=92=E9=98=B2=E3=81=90?=
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---
 src/formats/blueprint/codec.ts            | 12 ++++++--
 src/formats/blueprint/outlinerGroups.ts   | 31 +++++++++++++++++++
 src/tests/blueprintOutlinerGroups.test.ts | 36 +++++++++++++++++++++++
 3 files changed, 76 insertions(+), 3 deletions(-)
 create mode 100644 src/formats/blueprint/outlinerGroups.ts
 create mode 100644 src/tests/blueprintOutlinerGroups.test.ts

diff --git a/src/formats/blueprint/codec.ts b/src/formats/blueprint/codec.ts
index fc07e69e..ad6c9145 100644
--- a/src/formats/blueprint/codec.ts
+++ b/src/formats/blueprint/codec.ts
@@ -11,6 +11,7 @@ import { localize as translate } from '../../util/lang'
 import { sanitizeStorageKey } from '../../util/minecraftUtil'
 import { Variant } from '../../variants'
 import { upgradeAnimatedJavaBlueprint } from './dfu'
+import { groupsReferencedByOutliner } from './outlinerGroups'
 import * as blueprintSettings from './settings'
 
 // region Codec
@@ -150,7 +151,10 @@ export const BLUEPRINT_CODEC = registerDeletableHandlerPatch({
 				}
 
 				if (model.groups) {
-					for (const template of model.groups) {
+					for (const template of groupsReferencedByOutliner(
+						model.groups,
+						model.outliner
+					)) {
 						// @ts-expect-error - missing UUID arg
 						new Group(template, template.uuid).init()
 					}
@@ -291,13 +295,15 @@ export const BLUEPRINT_CODEC = registerDeletableHandlerPatch({
 					model.elements.push(element.getSaveCopy?.(!!model.meta))
 				}
 
+				const outliner = Outliner.toJSON()
+
 				model.groups = []
-				for (const group of Group.all) {
+				for (const group of groupsReferencedByOutliner(Group.all, outliner)) {
 					// @ts-expect-error - missing arg
 					model.groups.push(group.getSaveCopy(false))
 				}
 
-				model.outliner = Outliner.toJSON()
+				model.outliner = outliner
 
 				model.textures = []
 				for (const texture of Texture.all) {
diff --git a/src/formats/blueprint/outlinerGroups.ts b/src/formats/blueprint/outlinerGroups.ts
new file mode 100644
index 00000000..685ae381
--- /dev/null
+++ b/src/formats/blueprint/outlinerGroups.ts
@@ -0,0 +1,31 @@
+interface GroupWithUUID {
+	uuid?: unknown
+}
+
+interface OutlinerGroupEntry {
+	uuid?: unknown
+	children?: unknown
+	content?: unknown
+}
+
+export function groupsReferencedByOutliner<T extends GroupWithUUID>(
+	groups: readonly T[],
+	outliner: readonly unknown[] | undefined
+): T[] {
+	if (outliner === undefined) return [...groups]
+
+	const referencedUUIDs = new Set<string>()
+	function visit(entries: readonly unknown[]) {
+		for (const entry of entries) {
+			if (typeof entry !== 'object' || entry === null || Array.isArray(entry)) continue
+
+			const group = entry as OutlinerGroupEntry
+			if (typeof group.uuid === 'string') referencedUUIDs.add(group.uuid)
+			if (Array.isArray(group.children)) visit(group.children)
+			if (Array.isArray(group.content)) visit(group.content)
+		}
+	}
+
+	visit(outliner)
+	return groups.filter(group => typeof group.uuid === 'string' && referencedUUIDs.has(group.uuid))
+}
diff --git a/src/tests/blueprintOutlinerGroups.test.ts b/src/tests/blueprintOutlinerGroups.test.ts
new file mode 100644
index 00000000..0d830eca
--- /dev/null
+++ b/src/tests/blueprintOutlinerGroups.test.ts
@@ -0,0 +1,36 @@
+import { describe, expect, it } from 'vitest'
+import { groupsReferencedByOutliner } from '../formats/blueprint/outlinerGroups'
+
+describe('groupsReferencedByOutliner', () => {
+	it('collects nested children and legacy content entries while ignoring UUID strings', () => {
+		const groups = [
+			{ uuid: 'root' },
+			{ uuid: 'child' },
+			{ uuid: 'legacy' },
+			{ uuid: 'string-entry' },
+			{ uuid: 'orphan' },
+		]
+
+		const referenced = groupsReferencedByOutliner(groups, [
+			{
+				uuid: 'root',
+				children: [{ uuid: 'child', content: [{ uuid: 'legacy' }, 'string-entry'] }],
+			},
+			'string-entry',
+		])
+
+		expect(referenced.map(group => group.uuid)).toEqual(['root', 'child', 'legacy'])
+	})
+
+	it('keeps all groups when outliner is undefined', () => {
+		const groups = [{ uuid: 'first' }, { uuid: 'second' }]
+
+		expect(groupsReferencedByOutliner(groups, undefined)).toEqual(groups)
+	})
+
+	it('excludes all groups for a defined empty outliner', () => {
+		const groups = [{ uuid: 'orphan' }]
+
+		expect(groupsReferencedByOutliner(groups, [])).toEqual([])
+	})
+})