add basic implementation for attributes

packages/core/src/utils/getAttributesFromExtensions.ts

@@ -0,0 +1,38 @@
+import {
+  Extensions, Attributes, Attribute, ExtensionAttribute,
+} from '../types'
+import splitExtensions from './splitExtensions'
+
+export default function getAttributesFromExtensions(extensions: Extensions) {
+  const allAttributes: ExtensionAttribute[] = []
+
+  const { nodeExtensions } = splitExtensions(extensions)
+
+  const defaultAttribute: Required<Attribute> = {
+    default: null,
+    rendered: true,
+    renderHTML: () => ({}),
+    parseHTML: () => null,
+  }
+
+  nodeExtensions.forEach(extension => {
+    const context = {
+      options: extension.options,
+    }
+
+    const attributes = extension.createAttributes.bind(context)() as Attributes
+
+    Object.entries(attributes).forEach(([name, attribute]) => {
+      allAttributes.push({
+        type: extension.name,
+        name,
+        attribute: {
+          ...defaultAttribute,
+          ...attribute,
+        },
+      })
+    })
+  })
+
+  return allAttributes
+}