Unable to run tests with julia 1.11.5 if `julia.NumThreads` is not set

[stemann]

I am unable to run tests from the VS Code Julia REPL after updating Julia from 1.11.4 to 1.11.5 - testing fails with:

ERROR: julia: -t,--threads=<n>[,auto|<m>]; n must be an integer >= 1

Testing from a separate Julia REPL works just fine.

This is likely due to a combination of not setting julia.NumThreads and JuliaLang/Pkg.jl#4141

Likely solution is to not set JULIA_NUM_THREADS if julia.NumThreads is undefined.

Testing from the VS Code Julia REPL:

julia> versioninfo()
Julia Version 1.11.5
Commit 760b2e5b739 (2025-04-14 06:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (x86_64-apple-darwin24.0.0)
  CPU: 16 × Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, skylake)
Threads: 1 default, 0 interactive, 1 GC (on 16 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 
  JULIA_PKG_USE_CLI_GIT = true

(Example) pkg> test
  No Changes to `~/dev/julia/Example.jl/Project.toml`
  No Changes to `~/dev/julia/Example.jl/Manifest.toml`
     Testing Example
      Status `/private/var/folders/s1/xwq_jtwc8xld63006s6ny0n80000gn/T/jl_ggVXG0/Project.toml`
  [7876af07] Example v0.5.5 `~/dev/julia/Example.jl`
  [8dfed614] Test v1.11.0
      Status `/private/var/folders/s1/xwq_jtwc8xld63006s6ny0n80000gn/T/jl_ggVXG0/Manifest.toml`
  [7876af07] Example v0.5.5 `~/dev/julia/Example.jl`
  [2a0f44e3] Base64 v1.11.0
  [b77e0a4c] InteractiveUtils v1.11.0
  [56ddb016] Logging v1.11.0
  [d6f4376e] Markdown v1.11.0
  [9a3f8284] Random v1.11.0
  [ea8e919c] SHA v0.7.0
  [9e88b42a] Serialization v1.11.0
  [8dfed614] Test v1.11.0
     Testing Running tests...
ERROR: julia: -t,--threads=<n>[,auto|<m>]; n must be an integer >= 1
ERROR: Package Example errored during testing

[luraess]

Hitting similar issue

julia> versioninfo()
Julia Version 1.11.5
Commit 760b2e5b739 (2025-04-14 06:53 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 8 × Apple M2
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, apple-m2)
Threads: 1 default, 0 interactive, 1 GC (on 4 virtual cores)
Environment:
  JULIA_EDITOR = code
  JULIA_NUM_THREADS = 0 

On my end it seems that I had by default

"julia.NumThreads": 0,

in VS code settings.json.

Num threads were somehow ignored when testing from REPL in VS code in 1.11.4, but now fail as above.

[luraess]

Does it also handle the case when the default is

"julia.NumThreads": 0,

?

[stemann]

No.

Why set num threads to zero?

[luraess]

IDK - this was the issue on my side, although I did not set it to 0 explicitly (IDK if this was some default settings)

[stemann]

The default is null: https://github.com/julia-vscode/julia-vscode/blob/v1.139.0/package.json#L1048-L1057

[sairus7]

I've got the same error with "julia.NumThreads": null, it only worked with "auto" value on Julia 1.11.5.

[stemann]

Yeah, that would likely also trigger the issue. Should be fixed with #3800.

[Kevin-Mattheus-Moerman]

Had the same issue with both VS Code and Codium. Testing from a terminal session did not produce the error for me, so somehow this relates to the Julia VS Code package too I think.

For both VS Code and Codium the file settings.json had

"julia.NumThreads": 0

The error went away if I changed it to:

"julia.NumThreads": 1

Or

"julia.NumThreads": "auto"