Let Spawn take an asset over an edge and find a child by name (#237)

An asset could only be picked as a setting on the Spawn node. It could
not be wired in, held in a variable or put into a list. Finding an
object below the own one needed a scene-wide search by name.

- "Asset" is now a kind like Animation or Sound: port, variable, list
  item and a new "Asset" literal node, with its own cube icon.
- Spawn and Is asset have an `asset` input. It uses the key of the old
  setting, so a saved asset reads as the value of the input and older
  projects keep spawning without a migration.
- New node "Child by name" searches below an object level by level.
  A child wins over a grandchild of the same name. Nothing found or no
  object gives null.

Tests:
- ./check.sh: 168 files, 2453 tests, CHECK EXIT 0.
- 9 new unit tests in tests/core/asset-kind.test.ts, catalog cases for
  Spawn, Is asset, Child by name and the literal.
- e2e 6z-ii (2 checks): node rows and a real drag of the literal onto
  `asset`. e2e 6: 119 checks passed. Spawn checks in 3 and 9 passed.
- Counter-checks: depth-first search fails 1, Spawn reading only the
  old setting fails 3, runtime ignoring the parent fails 1.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/graph/nodes/action/Spawn.ts

@@ -1,20 +1,20 @@
 import type { NodeDef } from '../../NodeRegistry';
-import { asEntity, asNumber } from '../../values';
-import { assetParam, exec, num, obj } from '../shared';
+import { asEntity, asNumber, asString } from '../../values';
+import { assetPort, exec, num, obj } from '../shared';
 
-import { textOf } from '../../../model/Properties';
 export const Spawn: NodeDef = {
   type: 'Spawn',
   label: 'Spawn',
   category: 'action',
   description:
     'Creates a new instance of an asset in the running scene at (x, y, z) – local to the parent when one is ' +
-    'connected, world coordinates otherwise. Outputs the new object.',
-  inputs: [exec(), num('x'), num('y'), num('z'), obj('parent')],
+    'connected, world coordinates otherwise. The asset is picked on the node or arrives over an edge, from ' +
+    'an Asset literal, a variable or a list item. Outputs the new object.',
+  inputs: [exec(), assetPort(), num('x'), num('y'), num('z'), obj('parent')],
   outputs: [exec(), obj('object')],
-  params: [assetParam],
-  run: (ctx, inputs, params) => {
-    const assetId = textOf(params.asset ?? '');
+  params: [],
+  run: (ctx, inputs) => {
+    const assetId = asString(inputs.asset);
     const position = { x: asNumber(inputs.x), y: asNumber(inputs.y), z: asNumber(inputs.z) };
     const spawned = assetId ? ctx.spawn(assetId, position, asEntity(inputs.parent)) : null;
     if (!spawned) ctx.log(assetId ? `Spawn: asset ${assetId} not found` : 'Spawn: no asset selected');

src/core/graph/nodes/data/ChildByName.ts

@@ -0,0 +1,20 @@
+import type { NodeDef } from '../../NodeRegistry';
+import { asEntity, asString } from '../../values';
+import { obj, str } from '../shared';
+
+export const ChildByName: NodeDef = {
+  type: 'ChildByName',
+  label: 'Child by name',
+  category: 'data',
+  description:
+    'Finds an object by its name below the given one – among its children, their children and so on. ' +
+    'The nearest level wins; within a level, the first in hierarchy order. Nothing when none is called so.',
+  inputs: [obj('object'), str('name')],
+  outputs: [obj('child')],
+  params: [],
+  run: (ctx, inputs) => {
+    const parent = asEntity(inputs.object);
+    const name = asString(inputs.name);
+    return { outputs: { child: parent ? ctx.childByName(parent, name) : null } };
+  },
+};

src/core/graph/nodes/data/IsAsset.ts

@@ -1,18 +1,17 @@
 import type { NodeDef } from '../../NodeRegistry';
-import { asEntity } from '../../values';
-import { assetParam, bool, obj } from '../shared';
+import { asEntity, asString } from '../../values';
+import { assetPort, bool, obj } from '../shared';
 
-import { textOf } from '../../../model/Properties';
 export const IsAsset: NodeDef = {
   type: 'IsAsset',
   label: 'Is asset',
   category: 'data',
   description: 'Whether an object is an instance of the chosen asset – the way to tell what you collided with.',
-  inputs: [obj('object')],
+  inputs: [obj('object'), assetPort()],
   outputs: [bool('result')],
-  params: [assetParam],
-  run: (_ctx, inputs, params) => {
-    const assetId = textOf(params.asset ?? '');
+  params: [],
+  run: (_ctx, inputs) => {
+    const assetId = asString(inputs.asset);
     return { outputs: { result: Boolean(assetId) && asEntity(inputs.object)?.assetId === assetId } };
   },
 };

src/core/graph/nodes/data/literals.ts

@@ -50,6 +50,11 @@ export const AnimationLiteral = literal(
   'animation',
   'A constant animation, for a "Play animation", "Pause animation" or "Stop animation" to work on.',
 );
+export const AssetLiteral = literal(
+  'Asset',
+  'asset',
+  'A constant placeable asset, for a "Spawn" to place or an "Is asset" to compare with.',
+);
 export const ListLiteral = literal(
   'List',
   'list',

src/core/graph/nodes/index.ts

@@ -38,6 +38,7 @@ import { FindText } from './data/FindText';
 import { FirstNotEmpty } from './data/FirstNotEmpty';
 import { Floor } from './data/Floor';
 import { GetPosition } from './data/GetPosition';
+import { ChildByName } from './data/ChildByName';
 import { IsAsset } from './data/IsAsset';
 import { IsEnabled } from './data/IsEnabled';
 import { IsHovered } from './data/IsHovered';
@@ -48,6 +49,7 @@ import { KeyIsDown } from './data/KeyIsDown';
 import { Length } from './data/Length';
 import {
   AnimationLiteral,
+  AssetLiteral,
   BooleanLiteral,
   ListLiteral,
   NumberLiteral,
@@ -160,6 +162,7 @@ export const BUILT_IN_NODES: readonly NodeDef[] = [
   Owner,
   Parent,
   ObjectByName,
+  ChildByName,
   NameOf,
   IsAsset,
   IsEnabled,
@@ -173,6 +176,7 @@ export const BUILT_IN_NODES: readonly NodeDef[] = [
   SoundLiteral,
   SceneLiteral,
   AnimationLiteral,
+  AssetLiteral,
   Add,
   Subtract,
   Multiply,

src/core/graph/nodes/shared.ts

@@ -49,6 +49,12 @@ export const keyParam: PropertyDef = { key: 'key', label: 'Key', kind: 'key', de
 /** No `assetTypes`: any placeable asset is a valid answer here. */
 export const assetParam: PropertyDef = { key: 'asset', label: 'Asset', kind: 'asset', default: '' };
 
+/**
+ * The `asset` input of `Spawn` and `Is asset`; unconnected, it shows the asset picker. The key is the
+ * one the setting had before it became a port, so a saved pick is the inline value now.
+ */
+export const assetPort = (): PortDef => ({ key: 'asset', label: 'asset', type: 'string', field: assetParam });
+
 /**
  * The `sound` input of the two sound nodes; unconnected, it shows the sound picker – the way
  * `machinePort` shows the machine picker. A `Sound` literal is what feeds it through an edge.