throw error for missing mark/node type

packages/core/src/helpers/getMarkType.ts

@@ -2,6 +2,10 @@ import { MarkType, Schema } from 'prosemirror-model'
 
 export default function getMarkType(nameOrType: string | MarkType, schema: Schema): MarkType {
   if (typeof nameOrType === 'string') {
+    if (!schema.marks[nameOrType]) {
+      throw Error(`There is no mark type named '${nameOrType}'. Maybe you forgot to add the extension?`)
+    }
+
     return schema.marks[nameOrType]
   }
 

packages/core/src/helpers/getNodeType.ts

@@ -2,6 +2,10 @@ import { NodeType, Schema } from 'prosemirror-model'
 
 export default function getNodeType(nameOrType: string | NodeType, schema: Schema): NodeType {
   if (typeof nameOrType === 'string') {
+    if (!schema.nodes[nameOrType]) {
+      throw Error(`There is no node type named '${nameOrType}'. Maybe you forgot to add the extension?`)
+    }
+
     return schema.nodes[nameOrType]
   }