Adds legacyNoBatch setting

Avoids batching properties after startup to more closely match Polymer 1 behavior.

lib/mixins/property-accessors.js

@@ -12,6 +12,7 @@ import '../utils/boot.js';
 import { dedupingMixin } from '../utils/mixin.js';
 import { camelToDashCase, dashToCamelCase } from '../utils/case-map.js';
 import { PropertiesChanged } from './properties-changed.js';
+import { legacyNoBatch } from '../utils/settings.js';
 
 // Save map of native properties; this forms a blacklist or properties
 // that won't have their values "saved" by `saveAccessorValue`, since
@@ -289,7 +290,14 @@ export const PropertyAccessors = dedupingMixin(superClass => {
      * @override
      */
     _definePropertyAccessor(property, readOnly) {
-      saveAccessorValue(this, property);
+      if (legacyNoBatch) {
+        const ready = this.__dataReady;
+        this.__dataReady = false;
+        saveAccessorValue(this, property);
+        this.__dataReady = ready;
+      } else {
+        saveAccessorValue(this, property);
+      }
       super._definePropertyAccessor(property, readOnly);
     }
 

lib/mixins/property-effects.js

@@ -19,7 +19,7 @@ import { camelToDashCase, dashToCamelCase } from '../utils/case-map.js';
 import { PropertyAccessors } from './property-accessors.js';
 /* for annotated effects */
 import { TemplateStamp } from './template-stamp.js';
-import { sanitizeDOMValue, legacyUndefined } from '../utils/settings.js';
+import { sanitizeDOMValue, legacyUndefined, legacyNoBatch } from '../utils/settings.js';
 
 // Monotonically increasing unique ID used for de-duping effects triggered
 // from multiple properties in the same turn
@@ -1481,6 +1481,9 @@ export const PropertyEffects = dedupingMixin(superClass => {
           this.__dataToNotify = this.__dataToNotify || {};
           this.__dataToNotify[property] = shouldNotify;
         }
+        if (legacyNoBatch) {
+          this._invalidateProperties();
+        }
         return true;
       }
       return false;

lib/utils/settings.js

@@ -177,3 +177,21 @@ export let legacyUndefined = false;
 export const setLegacyUndefined = function(useLegacyUndefined) {
   legacyUndefined = useLegacyUndefined;
 };
+
+/**
+ * Setting to retain the legacy Polymer 1 behavior for setting properties. Does
+ * not batch property sets.
+ */
+export let legacyNoBatch = false;
+
+/**
+ * Sets `legacyNoBatch` globally for all elements to enable legacy
+ * behavior for setting properties.
+ *
+ * @param {boolean} useLegacyNoBatch enable or disable legacy
+ * property setting behavior.
+ * @return {void}
+ */
+export const setLegacyNoBatch = function(useLegacyNoBatch) {
+  legacyNoBatch = useLegacyNoBatch;
+};