improve object constancy approach:

- the '_index' field now corresponds to the menu index
  in the user layout update menu container.
  This is a more 'consistent' field than e.g. the index in the menuData.
- the '_index' field is set at the default step
  -> no need to rely on relinkPrivateKeys.

Author: etpinard

src/components/updatemenus/defaults.js

@@ -26,7 +26,13 @@ module.exports = function updateMenusDefaults(layoutIn, layoutOut) {
             menuOut = {};
 
         menuDefaults(menuIn, menuOut, layoutOut);
+
+        // used on button click to update the 'active' field
         menuOut._input = menuIn;
+
+        // used to determine object constancy
+        menuOut._index = i;
+
         contOut.push(menuOut);
     }
 };

src/components/updatemenus/draw.js

@@ -125,28 +125,24 @@ module.exports = function draw(gd) {
 
 function makeMenuData(fullLayout) {
     var contOpts = fullLayout[constants.name],
-        menuData = [],
-        cnt = 0;
+        menuData = [];
 
     // Filter visible dropdowns and attach '_index' to each
     // fullLayout options object to be used for 'object constancy'
     // in the data join key function.
-    //
-    // Note that '_index' is relinked from update to update via
-    // Plots.supplyDefaults.
 
     for(var i = 0; i < contOpts.length; i++) {
         var item = contOpts[i];
 
-        if(item.visible) {
-            if(!item._index) item._index = cnt++;
-            menuData.push(item);
-        }
+        if(item.visible) menuData.push(item);
     }
 
     return menuData;
 }
 
+// Note that '_index' is set at the default step,
+// it corresponds to the menu index in the user layout update menu container.
+// This is a more 'consistent' field than e.g. the index in the menuData.
 function keyFunction(opts) {
     return opts._index;
 }

test/jasmine/tests/updatemenus_test.js

@@ -194,6 +194,27 @@ describe('update menus interactions', function() {
             expect(gd._fullLayout._pushmargin['updatemenu-0']).toBeUndefined();
             expect(gd._fullLayout._pushmargin['updatemenu-1']).toBeUndefined();
 
+            return Plotly.relayout(gd, {
+                'updatemenus[2]': {
+                    buttons: [{
+                        method: 'relayout',
+                        args: ['title', 'new title']
+                    }]
+                }
+            });
+        }).then(function() {
+            assertMenus([0]);
+            expect(gd._fullLayout._pushmargin['updatemenu-0']).toBeUndefined();
+            expect(gd._fullLayout._pushmargin['updatemenu-1']).toBeUndefined();
+            expect(gd._fullLayout._pushmargin['updatemenu-2']).toBeDefined();
+
+            return Plotly.relayout(gd, 'updatemenus[0].visible', true);
+        }).then(function() {
+            assertMenus([0, 0]);
+            expect(gd._fullLayout._pushmargin['updatemenu-0']).toBeDefined();
+            expect(gd._fullLayout._pushmargin['updatemenu-1']).toBeUndefined();
+            expect(gd._fullLayout._pushmargin['updatemenu-2']).toBeDefined();
+
             done();
         });
     });