Ensure that marshalArgs pulls wildcard info value from __data

lib/mixins/property-effects.js

@@ -964,6 +964,19 @@ function parseArg(rawArg) {
   return a;
 }
 
+function getArgValue(data, props, path) {
+  let value = get(data, path);
+  // when data is not stored e.g. `splices`, get the value from changedProps
+  // TODO(kschaaf): Note, this can cause a rare issue where the wildcard
+  // info.value could pull a stale value out of changedProps during a reentrant
+  // change that sets the value back to undefined.
+  // https://github.com/Polymer/polymer/issues/5479
+  if (value === undefined) {
+    value = props[path];
+  }
+  return value;
+}
+
 // data api
 
 /**
@@ -979,11 +992,8 @@ function parseArg(rawArg) {
  * @private
  */
 function notifySplices(inst, array, path, splices) {
-  let splicesPath = path + '.splices';
-  inst.notifyPath(splicesPath, { indexSplices: splices });
+  inst.notifyPath(path + '.splices', { indexSplices: splices });
   inst.notifyPath(path + '.length', array.length);
-  // Null here to allow potentially large splice records to be GC'ed.
-  inst.__data[splicesPath] = {indexSplices: null};
 }
 
 /**
@@ -2140,37 +2150,23 @@ export const PropertyEffects = dedupingMixin(superClass => {
      */
     _marshalArgs(args, path, props) {
       const data = this.__data;
-      let values = [];
+      const values = [];
       for (let i=0, l=args.length; i<l; i++) {
-        let arg = args[i];
-        let name = arg.name;
-        let v;
-        if (arg.literal) {
-          v = arg.value;
-        } else {
-          if (arg.structured) {
-            v = get(data, name);
-            // when data is not stored e.g. `splices`
-            if (v === undefined) {
-              v = props[name];
-            }
+        let {name, structured, wildcard, value, literal} = args[i];
+        if (!literal) {
+          if (wildcard) {
+            const matches = isDescendant(name, path);
+            const pathValue = getArgValue(data, props, matches ? path : name);
+            value = {
+              path: matches ? path : name,
+              value: pathValue,
+              base: matches ? get(data, name) : pathValue
+            };
           } else {
-            v = data[name];
+            value = structured ? getArgValue(data, props, name) : data[name];
           }
         }
-        if (arg.wildcard) {
-          // Only send the actual path changed info if the change that
-          // caused the observer to run matched the wildcard
-          let baseChanged = (name.indexOf(path + '.') === 0);
-          let matches = (path.indexOf(name) === 0 && !baseChanged);
-          values[i] = {
-            path: matches ? path : name,
-            value: matches ? props[path] : v,
-            base: v
-          };
-        } else {
-          values[i] = v;
-        }
+        values[i] = value;
       }
       return values;
     }