Support vscode and intellij debuggers

[nyurik]

I have been trying to attach VSCode debugger to Clippy uitests, as I think Rust internal code is probably the most complex in the Rust ecosystem, and could really benefit from a step-by-step debugger with variable visualization. Internally, Clippy uses ui-test as an alternative harness. I documented in the CodeLLDB repo, but it seems there might need to be more communication between the maintainers to make it easier to debug.

I have also tried to use IntelliJ's Rust to debug Clippy, and if I manually supply LD_LIBRARY_PATH to the custom rustc toolchain, it fails because IntelliJ automatically adds --format=json -Z unstable-options --show-output - and fails because format does not understand json value. I wonder if ui_test should have the same CLI args as the default harness, or if there should be a well documented way for IDEs to attach to a non-default-harness tests? Thx!

/home/nyurik/dev/rust/lang/rust-clippy/target/debug/deps/compile_test-005862df71ed05a6 --format=json -Z unstable-options --show-output

[oli-obk]

wonder if ui_test should have the same CLI args as the default harness,

Yes it should!

Anything else I can do to improve the "test failed, rerun with more flags/in gdb/logging" is a good thing, so I wanna do more than that, but it's a good minimal bar to meet