Include parent testset descriptions in immediate test report

[tkf]

With this PR, the failure messages printed immediately after the test failure (i.e., not Test Summary) include testset descriptions of all parent test sets. This clarifies the context in which the failure occurs. This is important especially in Julia CI (Base.runtests) which does not print Test Summary. Without a change like this, heavily parameterized test like stdlib/LinearAlgebra/test/addmul.jl cannot produce any meaningful failure message (JuliaLang/LinearAlgebra.jl#655).

Some examples. The contents between Test Set: and Test Failed at are added in this PR:

julia> @testset "first level test set" begin @test false end
Test Set: first level test set
Test Failed at REPL[3]:1
  Expression: false
Stacktrace:
 [1] top-level scope at REPL[3]:1
 [2] top-level scope at /home/takafumi/repos/watch/_wt/julia/parentset/usr/share/julia/stdlib/v1.3/Test/src/Test.jl:1137
 [3] top-level scope at REPL[3]:1
Test Summary:        | Fail  Total
first level test set |    1      1
ERROR: Some tests did not pass: 0 passed, 1 failed, 0 errored, 0 broken.

julia> @testset "first level test set" begin
           @testset "second level test set" begin
               @testset "third level test set" begin
                   @test false
               end
           end
       end
Test Set:
first level test set
  second level test set
    third level test set
Test Failed at REPL[4]:4
  Expression: false
Stacktrace:
 [1] top-level scope at REPL[4]:4
 [2] top-level scope at /home/takafumi/repos/watch/_wt/julia/parentset/usr/share/julia/stdlib/v1.3/Test/src/Test.jl:1137
 [3] top-level scope at REPL[4]:4
 [4] top-level scope at /home/takafumi/repos/watch/_wt/julia/parentset/usr/share/julia/stdlib/v1.3/Test/src/Test.jl:1137
 [5] top-level scope at REPL[4]:3
 [6] top-level scope at /home/takafumi/repos/watch/_wt/julia/parentset/usr/share/julia/stdlib/v1.3/Test/src/Test.jl:1137
 [7] top-level scope at REPL[4]:2
Test Summary:            | Fail  Total
first level test set     |    1      1
  second level test set  |    1      1
    third level test set |    1      1
ERROR: Some tests did not pass: 0 passed, 1 failed, 0 errored, 0 broken.

[andreasnoack]

I think this is a good change. Please speak out if you have any objections.

[vtjnash]

WeakRef seems like the wrong choice, why not just a normal reference? Otherwise, seems like @andreasnoack already approved this and so it's good to merge.

[tkf]

I removed WeakRef

[tkf]

@vtjnash Do you want to review the post-merge diff? Or can I merge this?

[DilumAluthge]

You'll need to fix the doctest failures.

[vtjnash]

I don't remember ever looking at this before

[rfourquet]

Unless I'm missing something, given that the parent testsets are stored in the task local storage, it doesn't seem necessary to add parent as a field of DefaultTestSet nor to add the subtestset function, strictly for the purpose of including parent testsets in test report (it might be useful for other reasons though?)

[vtjnash]

Thanks @rfourquet for review. I agree: since we got to this record function by calling get_testset, and that function had the full list of testset parents already, it looks like we don't need to add a field to do this printing.

[tkf]

Thanks, @rfourquet. Yes, that's a good point. I don't remember why I didn't take that strategy. It's probably easy to fix.