Unit test for checking if table view from link list can be sync'ed

[kneth]

Translation of realm/realm-java#1886 to core/C++ that is, it is as close to how the Java binding is implemented as possible. A seg. fault happens in sync_if_needed().

Question to @realm/core: Is the Java binding doing something wrong?

Fun fact: Merging in #1392 does not resolved the issue.

[finnschiermer]

What's this?

[finnschiermer]

static_cast, then assignment? Is core supposed to support this use?

[simonask]

Struck me as suspicious too — a lot of methods on Query return Query&, so this is at high risk of operating on either temporaries or modifying the underlying Query for the TableView.

[teotwaki]

TableView::get_query returns a const Query, which this static_cast casts away. An equivalent form would be:

    Query query = const_cast<Query*>(&view.get_query())->get_table()->where(table1->get_linklist(0, 0));

Whether that's legal or not is another matter.

[danielpovlsen]

It must be copied then, because afaik static_cast cannot touch constness.

[teotwaki]

No, ::get_table() is not const.

[simonask]

static_cast indeed cannot cast away constness. So this line is correct, even if it's written in a convoluted way. :-)

[finnschiermer]

I think we should change our API to minimize this kind of usage if possible. Why is there even a get_query() on a TableView?

[simonask]

+1 to what @finnschiermer said

[kneth]

Link query on a table view.

[finnschiermer]

Why do you need to use get_query on the table view. Do you usually do that?

[kneth]

You can't query a table view directly so you can to create a new query using the table view as a filter. Instead if get_query().get_table(), you could do get_parent().

[zaki50]

Java code is:
object.getColumnRealmList().where().findAll();

To minimize the code, there are no conditions now after where() but there are some conditions usually.

[rrrlasse]

@kneth I found the real cause of the crash now (it wasn't a bug in move_last_over() anyway). It occurs because your query is refering to a LinkList that you deleted earlier:

Query query = static_cast<Query>(view.get_query()).get_table()->where(table1->get_linklist(0, 0)); ... table1->move_last_over(0); ... view2.sync_if_needed();

And sure, the code could be beautified and get_query() is also error prone to use (TableView may depend on a chain of further older queries, or may originate from something else than a Query, etc, etc).

[kneth]

@rrrlasse Why does is_attached() then return true?

[kneth]

@rrrlasse Will you create an issue about is_attached() should return false? When you do, you can either use this PR as a unit test or just close it.

[kneth]

I have created #1413 and closing this one.