add support for generating slots from blender properties

src/utils/parser.js

@@ -13,9 +13,23 @@ function parse(gltf, { fileName = 'model', ...options } = {}) {
   const animations = gltf.animations
   const hasAnimations = animations.length > 0
 
+  /** @type {Record<string, Object3D[]> */
+  const slots = {}
+
   // Collect all objects
   const objects = []
-  gltf.scene.traverse((child) => objects.push(child))
+  gltf.scene.traverse((child) => {
+    objects.push(child);
+
+    // Collect slots
+    const slot = child.userData?.prop;
+    const hasSlot = (slot && typeof slot === "string" && slot.length > 0);
+    if (hasSlot)
+    {
+      const slotname = sanitizeSlotName(slot);
+      slots[slotname] ? slots[slotname].push(child) : (slots[slotname] = [child]);
+    }
+  })
 
   // Browse for duplicates
   const duplicates = {
@@ -75,6 +89,11 @@ function parse(gltf, { fileName = 'model', ...options } = {}) {
     return isVarName(name) ? `.${name}` : `['${name}']`
   }
 
+  /** Ensure that a slot is a valid variable name e.g. must not contain spaces */
+  function sanitizeSlotName(slotname) {
+    return slotname.replaceAll(/[^a-zA-Z0-9]/g, '');
+  }
+
   const rNbr = (number) => {
     return parseFloat(number.toFixed(Math.round(options.precision || 2)))
   }
@@ -219,17 +238,18 @@ function parse(gltf, { fileName = 'model', ...options } = {}) {
       duplicates.geometries[obj.geometry.uuid + obj.material.name] &&
       duplicates.geometries[obj.geometry.uuid + obj.material.name].count > (options.instanceall ? 0 : 1)
     let animated = gltf.animations && gltf.animations.length > 0
-    return { type, node, instanced, animated }
+    const hasSlots = obj.userData?.prop && typeof obj.userData.prop === "string" && obj.userData.prop.length > 0;
+    return { type, node, instanced, animated, hasSlots }
   }
 
   function equalOrNegated(a, b) {
     return (a.x === b.x || a.x === -b.x) && (a.y === b.y || a.y === -b.y) && (a.z === b.z || a.z === -b.z)
   }
 
   function prune(obj, children, result, oldResult, silent) {
-    let { type, animated } = getInfo(obj)
+    let { type, animated, hasSlots } = getInfo(obj)
     // Prune ...
-    if (!obj.__removed && !options.keepgroups && !animated && (type === 'group' || type === 'scene')) {
+    if (!obj.__removed && !options.keepgroups && !animated && !hasSlots && (type === 'group' || type === 'scene')) {
       /** Empty or no-property groups
        *    <group>
        *      <mesh geometry={nodes.foo} material={materials.bar} />
@@ -370,13 +390,24 @@ function parse(gltf, { fileName = 'model', ...options } = {}) {
     // Bail out if the object was pruned
     if (pruned !== undefined) return pruned
 
-    // Close tag
-    result += `${children.length ? '>' : '/>'}\n`
+    // Add custom slots if defined in the object's userData 
+    // E.g. userData: { "prop" : "mySlot" } becomes `{ mySlot }`
+    const slot = obj.userData?.prop;
+    const hasSlot = (slot && typeof slot === "string" && slot.length > 0);
+    const hasContent = children.length || hasSlot;
 
-    // Add children and return
-    if (children.length) {
-      if (type === 'bone') result += children + `</primitive>`
-      else result += children + `</${type}>`
+
+    // Close tag if no children
+    result += `${hasContent ? '>' : '/>'}\n`
+
+    // Add children
+    if (children.length) result += `${children.trimEnd("\n")}\n`
+    // Add custom slot
+    if (hasSlot) result += `{${sanitizeSlotName(slot)}}\n`;
+    // Close tag
+    if (hasContent) {
+    	if (type === 'bone') result += `</primitive>`
+      	else result += `</${type}>`
     }
     return result
   }
@@ -440,10 +471,14 @@ function parse(gltf, { fileName = 'model', ...options } = {}) {
   } catch (e) {
     console.log('Error while parsing glTF', e)
   }
+
+  const slotParams = Object.keys(slots).length > 0 ? (Object.keys(slots).join(", ") + ", ") : "";
+
   const header = `/*
 ${options.header ? options.header : 'Auto-generated by: https://github.com/pmndrs/gltfjsx'} ${
     options.size ? `\nFiles: ${options.size}` : ''
   }
+
 ${parseExtras(gltf.parser.json.asset && gltf.parser.json.asset.extras)}*/`
   const hasPrimitives = scene.includes('<primitive')
   const result = `${options.types ? `\nimport * as THREE from 'three'` : ''}
@@ -465,7 +500,7 @@ ${parseExtras(gltf.parser.json.asset && gltf.parser.json.asset.extras)}*/`
             ? `
         const context = React.createContext(${options.types ? '{} as ContextType' : ''})
 
-        export function Instances({ children, ...props }${options.types ? ': JSX.IntrinsicElements["group"]' : ''}) {
+        export function Instances({ children, ${slotParams}...props }${options.types ? ': JSX.IntrinsicElements["group"]' : ''}) {
           const { nodes } = useGLTF('${url}'${options.draco ? `, ${JSON.stringify(options.draco)}` : ''})${
             options.types ? ' as GLTFResult' : ''
           }
@@ -486,7 +521,7 @@ ${parseExtras(gltf.parser.json.asset && gltf.parser.json.asset.extras)}*/`
             : ''
         }
 
-        export ${options.exportdefault ? 'default' : ''} function Model(props${
+        export ${options.exportdefault ? 'default' : ''} function Model({ ${slotParams}...props }${
           options.types ? ": JSX.IntrinsicElements['group']" : ''
         }) {
           ${hasInstances ? 'const instances = React.useContext(context);' : ''} ${