Support merging searches using shared context

[avit]

When merging search criteria, it's necessary to use the same join dependency with a shared alias tracker. This can be achieved by passing a context option when building a Search object.

I've added the option and exposed Context#alias_tracker.

[jonatack]

Thanks @avit :-) can you update so that the tests pass for Rails 3.0 and squash your commits?

[jonatack]

uninitialized constant ActiveRecord::Associations::AliasTracker

Rails 3.0 doesn't seem to be finding your new method.

[avit]

Ah, thank goodness for CI. I'll move things around.

I will also expose "join_sources" on the context. This will eventually enable something for chaining like search.or(search) which is essentially what we're doing in our application (searching by multiple filters).

[avit]

I reworked this to correctly support the different approaches used in each ActiveRecord version:

• 3.0 doesn't have AliasTracker so we can skip it there. It's not critical to have. All later versions define it.
• 3.0 doesn't have join_sources, and doesn't support using Arel::Join objects directly anyway: relation.joins(arel_outer_join) will output "INNER JOIN OUTER JOIN". Instead, 3.0 should use join_associations, which gets applied correctly.
• 3.1 and later has join_sources which works correctly and seems preferable.
• 4.1 no longer has join_associations, so by then you should be using join_sources.

There are some conditionals in the specs to reflect the version support.

[jonatack]

Thanks @avit, nice work 💚

Could you document this for everyone in the readme or wiki?

[avit]

Thanks for the quick merge! The details are in the wiki: Merging Searches

[jonatack]

Great! 🎉