Improve false negative on AlteredSliceTag (#6578)

The "altered" tag in the explore view shows up more often than it
should. By treating null, [] {}, undefined as identical will help reporting
only the differences that matter.

superset/assets/spec/javascripts/components/AlteredSliceTag_spec.jsx

@@ -284,4 +284,28 @@ describe('AlteredSliceTag', () => {
       expect(wrapper.instance().formatValue(filters, 'adhoc_filters')).toBe(expected);
     });
   });
+  describe('isEqualish', () => {
+    it('considers null, undefined, {} and [] as equal', () => {
+      const inst = wrapper.instance();
+      expect(inst.isEqualish(null, undefined)).toBe(true);
+      expect(inst.isEqualish(null, [])).toBe(true);
+      expect(inst.isEqualish(null, {})).toBe(true);
+      expect(inst.isEqualish(undefined, {})).toBe(true);
+    });
+    it('considers empty strings are the same as null', () => {
+      const inst = wrapper.instance();
+      expect(inst.isEqualish(undefined, '')).toBe(true);
+      expect(inst.isEqualish(null, '')).toBe(true);
+    });
+    it('considers deeply equal objects as equal', () => {
+      const inst = wrapper.instance();
+      expect(inst.isEqualish('', '')).toBe(true);
+      expect(inst.isEqualish({ a: 1, b: 2, c: 3 }, { a: 1, b: 2, c: 3 })).toBe(true);
+      // Out of order
+      expect(inst.isEqualish({ a: 1, b: 2, c: 3 }, { b: 2, a: 1, c: 3 })).toBe(true);
+
+      // Actually  not equal
+      expect(inst.isEqualish({ a: 1, b: 2, z: 9 }, { a: 1, b: 2, c: 3 })).toBe(false);
+    });
+  });
 });

superset/assets/src/components/AlteredSliceTag.jsx

@@ -12,6 +12,24 @@ const propTypes = {
   currentFormData: PropTypes.object.isRequired,
 };
 
+function alterForComparison(value) {
+  // Considering `[]`, `{}`, `null` and `undefined` as identical
+  // for this purpose
+  if (value === undefined || value === null || value === '') {
+    return null;
+  } else if (typeof value === 'object') {
+    if (Array.isArray(value) && value.length === 0) {
+      return null;
+    }
+    const keys = Object.keys(value);
+    if (keys && keys.length === 0) {
+      return null;
+    }
+  }
+  return value;
+}
+
+
 export default class AlteredSliceTag extends React.Component {
 
   constructor(props) {
@@ -45,13 +63,17 @@ export default class AlteredSliceTag extends React.Component {
       if (['filters', 'having', 'having_filters', 'where'].includes(fdKey)) {
         continue;
       }
-      if (!isEqual(ofd[fdKey], cfd[fdKey])) {
+      if (!this.isEqualish(ofd[fdKey], cfd[fdKey])) {
         diffs[fdKey] = { before: ofd[fdKey], after: cfd[fdKey] };
       }
     }
     return diffs;
   }
 
+  isEqualish(val1, val2) {
+    return isEqual(alterForComparison(val1), alterForComparison(val2));
+  }
+
   formatValue(value, key) {
     // Format display value based on the control type
     // or the value type