Check that profile path exists before sourcing

[lionel-]

Closes #966.

R ignores R_PROFILE and R_PROFILE_USER when they don't exist: https://github.com/wch/r-source/blob/ab34772818fcb3ec74ad1af4a38e1ac1410d7933/src/main/main.c#L721. We now do the same (with a logged warning) to avoid visible errors streamed on IOPub.

I've added a couple of tests and gathered all site file tests in kernel-nexstep.rs. These tests need to be run with cargo nexstep as they rely on unique process singletons. I'm not prepared to treat all of kernel.rs in this way just yet because many IDE affordances for running/debugging tests do not support nexstep.

Release Notes

Bug Fixes

• Fixed a bug in the R backend that caused visible errors when the R_PROFILE or R_PROFILE_USER environment variables were set to paths that don't exist (Verbose error when site file does not exist #966).

[DavisVaughan]

No blocking requests

But we should probably discuss our thoughts about nextest together soon!

[DavisVaughan]

I really think we should just call this r-profile.rs

IIUC we run tests in one of two ways:

• just test at the command line to run all tests with nextest
• The Run Test button that VS Code provides via rust-analyzer to run a single test

It is impossible to run the full suite of tests without cargo nextest, so it does not feel worth it to me to call out that you need it here. Other tests like test_inability_to_load_ragg_falls_back_to_base_graphics would also need such a call out. Our BUILDING.md mentions the need for nextest pretty clearly.

Do you run tests in a different way than the two mentioned here? This is the 2nd time we've had differing opinions here, so I think that suggests we somehow have different workflows or worldviews about this

[lionel-]

it is impossible to run the full suite of tests without cargo nextest, so it does not feel worth it to me to call out that you need it here.

It's possible to run a subset of the suite of tests with cargo test, and comes up regularly for me due to various tooling/IDE integrations. For instance "run tests for this module".

[lionel-]

cargo test is so deeply integrated in various Rust workflows that I think we'll be in an intermediate state for a while until test runners become indirected in these integrations due to the success of nextest.

[lionel-]

I renamed this to kernel-r-profile.rs as I think these integration tests should have a common prefix.

[DavisVaughan]

For instance "run tests for this module"

Yea this is the workflow difference between us that i was missing

That's a button for you in Zed?

[DavisVaughan]

Oh right, its "Run Tests" in VS Code. I remember opening this now nextest-rs/nextest#2253

[DavisVaughan]

I've reopened this as a rust-analyzer issue instead rust-lang/rust-analyzer#21137

[juliasilge]

Let me know if we won't be able to get this into Positron itself before we branch for release tomorrow. Thanks!