Support accessing members of a conditional value

[ranma42]

This changeset adds support for accessing a member of the result of a conditional expression.

It achieves this by folding the member access into the conditional.

Fixes #34589.

[ranma42]

Note that the updated baselines point to a missing CASE simplification (CASE WHEN nonNullableX THEN TRUE ELSE FALSE END -> nonNullableX).
Additionally, the test I implemented currently hits #28077 (neither join is really needed).

I would like to add a couple of missing test cases before marking as ready:

• different subclasses of a same type (see point 2 in Support projecting different navigations (but same type) via conditional operator #34589 (comment) )
• select'ing the conditional, then accessing multiple members

I am also thinking that it might be a good idea to write the tests so that they do not interact with #28077, so I will probably end up rewriting the existing test. What is the best place for these tests? (if I want to check the behavior on different subclasses, maybe InheritanceQueryTestBase makes more sense 🤔 )

[ranma42]

I extended the tests and kept them in GoW, as the different handling of subclassing is interesting.
In order to implement Conditional_Navigation_With_Member_Access_On_Related_Types I extended LocustHorde, which has the unfortunate side-effects of changing unrelated tests (adding a column in several SELECT queries).
I would love recommendations on possible improvements.

[Xriuk]

Hello, not sure if this is the right place for suggestions, but conditionals could be nested, to allow handling more than 2 options, like:

(test1 ? expr1 : (test2 ? expr2 : expr3)).Member
-> (test1 ? expr1.Member : (test2 ? expr2.Member : expr3.Member))

The nesting could also be in both branches.

Also the properties accessed could be deep like:

(test1 ? expr1 : (test2 ? expr2 : expr3)).Member1.Member2
-> (test1 ? expr1.Member1.Member2 : (test2 ? expr2.Member1.Member2 : expr3.Member1.Member2))

What I personally resorted to doing is when visiting a member first find out if it's part of a member chain with a conditional expression at the top, and save all the members along it.
Then recursively convert the conditional expression where each branch could be either another conditional expression or a generic expression which will get prepended to the previous members chain.
This seems to work for me

[ranma42]

@Xriuk your first example should already be taken care of by the recursive visit as follows:

(test1 ? expr1 : (test2 ? expr2 : expr3)).Member
->
(test1 ? expr1.Member : (test2 ? expr2 : expr3).Member)
->
(test1 ? expr1.Member : (test2 ? expr2.Member : expr3.Member))

The second one needs some additional attention... I'll try to extend the code (and tests)