VSCode: Missing DYLD_FALLBACK_LIBRARY_PATH config for test debugging

rust-analyzer version: fd3942eb6 2022-01-31 stable

rustc version: 1.56.0 (09c42c458 2021-10-18)

Running VSCode on macOS and attempting to debug a unit test through Lens results in a dyld crash; Library not loaded: @rpath/libtest-*dylib. Further investigation shows that setting

[lib]
proc-macro = true

in Cargo.toml always adds dynamic linking to libtest and libstd:

$: otool -l target/debug/deps/ra_repro-31a9e1719a1d9b00

...
Load command 14
          cmd LC_LOAD_DYLIB
      cmdsize 64
         name @rpath/libtest-587b2e5ab4fd237b.dylib (offset 24)
   time stamp 2 Wed Dec 31 16:00:02 1969
      current version 0.0.0
compatibility version 0.0.0
Load command 15
          cmd LC_LOAD_DYLIB
      cmdsize 64
         name @rpath/libstd-034b65e7f48264be.dylib (offset 24)
   time stamp 2 Wed Dec 31 16:00:02 1969
      current version 0.0.0
compatibility version 0.0.0
Load command 16
          cmd LC_LOAD_DYLIB
      cmdsize 56
         name /usr/lib/libSystem.B.dylib (offset 24)
   time stamp 2 Wed Dec 31 16:00:02 1969
      current version 1311.0.0
compatibility version 1.0.0
...

Encountering the dyld: Library not loaded error implies rust-analyzer does not properly set DYLD_FALLBACK_LIBRARY_PATH when debugging tests. Manually setting the envvar path fixes the problem, either by running:

export DYLD_FALLBACK_LIBRARY_PATH=$DYLD_FALLBACK_LIBRARY_PATH:/Users/[username]/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib

and manually executing the executable in the same terminal session

or by adding the following to VSCode's settings.json:

"rust-analyzer.debug.engineSettings": {
    "lldb": {
        "env": {
            "DYLD_FALLBACK_LIBRARY_PATH": "$DYLD_FALLBACK_LIBRARY_PATH:/Users/[username]/.rustup/toolchains/stable-aarch64-apple-darwin/lib/rustlib/aarch64-apple-darwin/lib"
        }
    }
}

These workarounds should not be necessary and debugging should work without them.

Start with VSCode Lens unit-test debugging and the LLDB engine settings described in the issue, then reproduce on macOS with a Cargo.toml containing proc-macro = true. Compare debugging with and without DYLD_FALLBACK_LIBRARY_PATH; done means the test launches without the manual environment-variable workaround.