Finish implementation of delete field from schema

spec/Schema.spec.js

@@ -520,4 +520,50 @@ describe('Schema', () => {
       });
     })
   });
+
+  it('can delete string fields and resave as number field', done => {
+    var obj1 = hasAllPODobject();
+    var obj2 = hasAllPODobject();
+    var p = Parse.Object.saveAll([obj1, obj2])
+    .then(() => config.database.loadSchema())
+    .then(schema => schema.deleteField('aString', 'HasAllPOD', config.database.db, 'test_'))
+    .then(() => new Parse.Query('HasAllPOD').get(obj1.id))
+    .then(obj1 => {
+      expect(obj1.get('aString')).toEqual(undefined);
+      obj1.set('aString', ['not a string', 'this time']);
+      obj1.save()
+      .then(obj1 => {
+        expect(obj1.get('aString')).toEqual(['not a string', 'this time']);
+        return new Parse.Query('HasAllPOD').get(obj2.id);
+      })
+      .then(obj2 => {
+        expect(obj2.get('aString')).toEqual(undefined);
+        done();
+      });
+    })
+  });
+
+  it('can delete pointer fields and resave as string', done => {
+    var obj1 = new Parse.Object('NewClass');
+    obj1.save()
+    .then(() => {
+      obj1.set('aPointer', obj1);
+      return obj1.save();
+    })
+    .then(obj1 => {
+      expect(obj1.get('aPointer').id).toEqual(obj1.id);
+    })
+    .then(() => config.database.loadSchema())
+    .then(schema => schema.deleteField('aPointer', 'NewClass', config.database.db, 'test_'))
+    .then(() => new Parse.Query('NewClass').get(obj1.id))
+    .then(obj1 => {
+      expect(obj1.get('aPointer')).toEqual(undefined);
+      obj1.set('aPointer', 'Now a string');
+      return obj1.save();
+    })
+    .then(obj1 => {
+      expect(obj1.get('aPointer')).toEqual('Now a string');
+      done();
+    });
+  });
 });

src/Schema.js

@@ -458,20 +458,32 @@ Schema.prototype.deleteField = function(fieldName, className, database, prefix)
         });
       }
 
-      let p = null;
       if (schema.data[className][fieldName].startsWith('relation')) {
         //For relations, drop the _Join table
-
+        return database.dropCollection(prefix + '_Join:' + fieldName + ':' + className)
-        p = database.dropCollection(prefix + '_Join:' + fieldName + ':' + className);
+        //Save the _SCHEMA object
+        .then(() => this.collection.update({ _id: className }, { $unset: {[fieldName]: null }}));
       } else {
         //for non-relations, remove all the data. This is necessary to ensure that the data is still gone
         //if they add the same field.
-        p = Promise.resolve();
+        return new Promise((resolve, reject) => {
+          database.collection(prefix + className, (err, coll) => {
+            if (err) {
+              reject(err);
+            } else {
+              return coll.update({}, {
+                "$unset": { [fieldName] : null },
+              }, {
+                multi: true,
+              })
+              //Save the _SCHEMA object
+              .then(() => this.collection.update({ _id: className }, { $unset: {[fieldName]: null }}))
+              .then(resolve)
+              .catch(reject);
+            }
+          });
+        });
       }
-      return p.then(() => {
-        //Save the _SCHEMA object
-        return Promise.resolve();
-      });
     });
   });
 }