Prevent history mutation during initialization (#1329)

* fix history on init

* fix setValue save logic

* update comment

packages/slate-react/src/plugins/before.js

@@ -109,9 +109,10 @@ function BeforePlugin() {
 
     // If the value's schema isn't the editor's schema, update it. This can
     // happen on the initialization of the editor, or if the schema changes.
+    // This change isn't save into history since only schema is updated.
     if (value.schema != editor.schema) {
       change
-        .setValue({ schema: editor.schema })
+        .setValue({ schema: editor.schema }, { save: false })
         .normalize()
     }
 

packages/slate/src/changes/on-value.js

@@ -14,9 +14,10 @@ const Changes = {}
  *
  * @param {Change} change
  * @param {Object|Value} properties
+ * @param {Object} options
  */
 
-Changes.setValue = (change, properties) => {
+Changes.setValue = (change, properties, options = {}) => {
   properties = Value.createProperties(properties)
   const { value } = change
 
@@ -24,7 +25,7 @@ Changes.setValue = (change, properties) => {
     type: 'set_value',
     properties,
     value,
-  })
+  }, options)
 }
 
 /**