Windows: test cleanup fails with `Access is denied (os error 5)` when a test spawns a lingering child process (MSVC mspdbsrv.exe)

[danx12]

Problem description

On Windows, a package test that passes still fails the whole run because rattler-build cannot remove its temporary test directory afterwards:

│ Testing commands:
│ ... cl /nologo /EHsc hello.c
│ hello.c
│ ... hello.exe
│ hello from cl.exe
╰─────────────────── (took 2 minutes)
Error:   × Test failed: failed to remove directory `...\test\test_<pkg>`: Access is denied. (os error 5)

The compiler command (cl.exe) succeeds and the program runs correctly. The error happens purely in the post-test cleanup (remove_dir_all of the test prefix).

Root cause: MSVC's cl.exe spawns a helper, mspdbsrv.exe (the PDB symbol server), which keeps running for a short while after cl.exe exits and holds an open handle inside the test directory. When rattler-build immediately tries to delete the directory, Windows refuses with os error 5 (Access is denied). This is a lingering-child-process file-lock, not a real test failure.

This looks like the same class of problem previously reported in #1431 (closed/completed), which also shows Access is denied. (os error 5) / os error 32 during build/test cleanup on Windows for Go- and JVM-based recipes.

Request

Currently the only options are to disable the test entirely or add a recipe-side sleep hack, since there is no flag to skip only the cleanup step.

Minimal reproducer

Any recipe whose test invokes the MSVC compiler reproduces it, because cl.exe always launches mspdbsrv.exe. Sketch:

tests:
  - script:
      - if: win
        then:
          - cl /nologo /EHsc hello.c   # spawns mspdbsrv.exe
          - hello.exe
    files:
      recipe:
        - hello.c

hello.c:

#include <stdio.h>
int main(void) { printf("hello from cl.exe\n"); return 0; }

The test passes, then rattler-build fails removing the test prefix with Access is denied. (os error 5).

Environment

• rattler-build: 0.69.0
• OS: Windows Server container (running as an administrator account)

[lucascolley]

It may be that I hit the same problem in conda-forge/circleci-feedstock#16 and conda-forge/staged-recipes#32124