Adds more expressive schema mismatch errors

spec/Schema.spec.js

@@ -808,4 +808,62 @@ describe('SchemaController', () => {
     });
     done();
   });
+
+  it('yields a proper schema mismatch error (#2661)', done => {
+    let anObject = new Parse.Object('AnObject');
+    let anotherObject = new Parse.Object('AnotherObject');
+    let someObject = new Parse.Object('SomeObject');
+    Parse.Object.saveAll([anObject, anotherObject, someObject]).then(() => {
+      anObject.set('pointer', anotherObject);
+      return anObject.save();
+    }).then(() => {
+      anObject.set('pointer', someObject);
+      return anObject.save();
+    }).then(() => {
+      fail('shoud not save correctly');
+      done();
+    }, (err) => {
+      expect(err instanceof Parse.Error).toBeTruthy();
+      expect(err.message).toEqual('schema mismatch for AnObject.pointer; expected Pointer<AnotherObject> but got Pointer<SomeObject>')
+      done();
+    });
+  });
+
+  it('yields a proper schema mismatch error bis (#2661)', done => {
+    let anObject = new Parse.Object('AnObject');
+    let someObject = new Parse.Object('SomeObject');
+    Parse.Object.saveAll([anObject, someObject]).then(() => {
+      anObject.set('number', 1);
+      return anObject.save();
+    }).then(() => {
+      anObject.set('number', someObject);
+      return anObject.save();
+    }).then(() => {
+      fail('shoud not save correctly');
+      done();
+    }, (err) => {
+      expect(err instanceof Parse.Error).toBeTruthy();
+      expect(err.message).toEqual('schema mismatch for AnObject.number; expected Number but got Pointer<SomeObject>')
+      done();
+    });
+  });
+
+  it('yields a proper schema mismatch error ter (#2661)', done => {
+    let anObject = new Parse.Object('AnObject');
+    let someObject = new Parse.Object('SomeObject');
+    Parse.Object.saveAll([anObject, someObject]).then(() => {
+      anObject.set('pointer', someObject);
+      return anObject.save();
+    }).then(() => {
+      anObject.set('pointer', 1);
+      return anObject.save();
+    }).then(() => {
+      fail('shoud not save correctly');
+      done();
+    }, (err) => {
+      expect(err instanceof Parse.Error).toBeTruthy();
+      expect(err.message).toEqual('schema mismatch for AnObject.pointer; expected Pointer<SomeObject> but got Number')
+      done();
+    });
+  });
 });

src/Controllers/SchemaController.js

@@ -298,6 +298,13 @@ const dbTypeMatchesObjectType = (dbType, objectType) => {
   return false;
 }
 
+const typeToString = (type) => {
+  if (type.targetClass) {
+    return `${type.type}<${type.targetClass}>`;
+  }
+  return `${type.type || type}`;
+}
+
 // Stores the entire schema of the app in a weird hybrid format somewhere between
 // the mongo format and the Parse format. Soon, this will all be Parse format.
 export default class SchemaController {
@@ -591,7 +598,7 @@ export default class SchemaController {
         if (!dbTypeMatchesObjectType(expectedType, type)) {
           throw new Parse.Error(
             Parse.Error.INCORRECT_TYPE,
-            `schema mismatch for ${className}.${fieldName}; expected ${expectedType.type || expectedType} but got ${type.type}`
+            `schema mismatch for ${className}.${fieldName}; expected ${typeToString(expectedType)} but got ${typeToString(type)}`
           );
         }
         return this;