IllegalStateExceptions thrown when using query.selectKeys()

[natario1]

I am inclined to believe that this is a Android SDK bug rather than parse-server.

Steps to reproduce:

1. Create a TestTable like the following, with just to objects:

    key:        foo            bar           else
                “yes”          111           “unwanted key”
                “yes”                        “unwanted key”
   

   That is,

    ParseObject o1 = new ParseObject(“TestTable”);
    o1.set(“foo”, “yes”);
    o1.set(“bar”, 111);
    o1.set(“else”, “unwanted key”);
    o1.save();
    ParseObject o2 = new ParseObject(“TestTable”);
    o2.set(“foo”, “yes”);
    o2.set(“else”, “unwanted key”);
    o2.save();
   

2. No issues arise if you call find() as is:

    ParseQuery q = ParseQuery.getQuery(“TestTable”);
    List<ParseObject> objs = q.find();
   

   Calling obj.getInt(“bar”) will return 111 for the first object, 0 for the second.
   That’s what we are used to.

3. But if we want to exclude the “else” key,

    ParseQuery q = ParseQuery.getQuery(“TestTable”);
    q.selectKeys(Arrays.asList(“foo”, “bar”));
    List<ParseObject> objs = q.find();
   

   Calling obj.getInt(“bar”) returns 111 for the first object indeed, but throws an exception for the first object, the IllegalStateException asking you to fetch the object.

I hope the report is clear: if a selected key exists in the server but is simply undefined, obj.has(“key”) incorrectly returns false obj.get(“key”) incorrectly throws. This makes selectKeys() useless for any table that might have some undefined data among the selected keys. I am surprised this was not brought up yet.

Note: make sure to wipe out app cache between point 2 or 3, or 3 will work because the object is cached. Or, just test 3. before testing 2.

Thank you @rogerhu for stepping up, I am happy to see this back on track.

[natario1]

I have looked for issues in the JSON decoding but there aren't. As far as I can see the issue is much simpler (and harder to fix):

Get calls do not fail if object.isDataAvailable() || estimatedData.containsKey(key) returns true. That is, object is complete, or it is not but we got key data from the server.

For our object estimatedData.containsKey(key) will always be false, because the server is not sending that data neither in case 2 nor 3. The bad thing is that isDataAvailable() (i.e. object is complete) returns true in case 2, and false in case 3, because we selected some keys.

The worst part (for this bug) is that this behavior makes actually sense, e.g. it’s clear that in case 3 object.isDataAvailable() || estimatedData.containsKey(key) must be false. I can’t see any elegant fix. We might have to add a safeKeys set to ParseObject and check that key is contained there to enable get access.

[rogerhu]

So iOS throws an exception too:

2017-03-12 10:01:42.423 ParseFun[34091:3327744] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Key "elseKey" has no data. Call fetchIfNeeded before getting its value.'

class TestTable: NSObject {
    var foo: String
    var bar: String
    var elseKey : String

    override init() {
        self.foo = ""
        self.bar = ""
        self.elseKey = ""
    }
}

Saving the entries:

       let o1 = PFObject(className: "TestTable");
        o1["foo"] = "yes";
        o1["bar"] = 111;
        o1["elseKey"] = "unwanted key";

        do {
         try o1.save()
        } catch {
            print("Error saving o1")
        }
        let o2 = PFObject(className: "TestTable");
        o2["foo"] = "yes";
        o2["elseKey"] = "unwanted key";

        do {
            try o2.save()
        } catch {
            print("Error saving o2")
        }

Querying the data will crash if selectKeys() is used:

        let pf = PFQuery(className: "TestTable");
        do {
            // comment/uncomment this line
            pf.selectKeys(["foo", "bar"]);
            let objs = try pf.findObjects()
            print("objs: \(objs)")

            for obj in objs {
                let fooVal = obj.value(forKey: "foo") as! String
                let elseVal = obj.value(forKey: "elseKey") as! String
                print("obj: fooVal: \(fooVal) elseKey: \(elseVal)")
            }
        } catch {
            print("Error querying")
        }

[natario1]

@rogerhu I can barely read iOS code, but I think you should try obj.value(forKey: “bar”) , that’s where we fail for o2. Throwing on elseKey access seems legit because it was not selected.

[rogerhu]

            for obj in objs {
                let fooVal = obj.value(forKey: "foo") as! String
                let barVal = obj.value(forKey: "bar") as! Int
                print("obj: fooVal: \(fooVal) barVal: \(barVal)")
            }

Outputs:

obj: fooVal: yes barVal: 111
fatal error: unexpectedly found nil while unwrapping an Optional value

[rogerhu]

Let me change to optional...1 sec

[rogerhu]

Works fine:

            for obj in objs {
                let fooVal = obj.value(forKey: "foo") as! String
                let barVal = obj.value(forKey: "bar") as? Int
                print("obj: fooVal: \(fooVal) barVal: \(barVal)")
            }

obj: fooVal: yes barVal: Optional(111)
obj: fooVal: yes barVal: nil