wip: add getExtensionField

packages/core/src/helpers/getExtensionField.ts

@@ -0,0 +1,25 @@
+import { AnyExtension, AnyObject, RemoveThis } from '../types'
+
+export default function getExtensionField<T = any>(
+  extension: AnyExtension,
+  field: string,
+  context: AnyObject = {},
+): RemoveThis<T> {
+
+  if (extension.config[field] === undefined && extension.parent) {
+    return getExtensionField(extension.parent, field, context)
+  }
+
+  if (typeof extension.config[field] === 'function') {
+    const value = extension.config[field].bind({
+      ...context,
+      parent: extension.parent
+        ? getExtensionField(extension.parent, field, context)
+        : null,
+    })
+
+    return value
+  }
+
+  return extension.config[field]
+}