"Global state has changed" warning

Nobody has claimed this yet.

Transferred from paul-buerkner/brms#1670

We rely on brms / rstan in the report package, and we have a workflow checking for warnings in tests. The workflow is failing due to a warning caused by brms / rstan (see easystats/report#448),

Global state has changed

Essentially, the warning seems to arise from a test simply calling the brms::brms() function as below:

model <- suppressMessages(suppressWarnings(brms::brm(
    mpg ~ qsec + wt,data = mtcars, refresh = 0, iter = 1, seed = 333)))

Generates that "Global state has changed" warning. The detailed error from the workflow is available e.g., here: https://github.com/easystats/report/actions/runs/9797434007/job/27054023826?pr=447#step:5:196

── Warning (test-report.brmsfit.R:3:1): report.brms ────────────────────────────
Global state has changed:
     names(before[[4]])                | names(after[[4]])                      
[94] "PIPX_HOME"                       | "PIPX_HOME"                       [94] 
[95] "PKGCACHE_HTTP_VERSION"           | "PKGCACHE_HTTP_VERSION"           [95] 
[96] "PKGLOAD_PARENT_TEMPDIR"          | "PKGLOAD_PARENT_TEMPDIR"          [96] 
                                       - "PKG_CPPFLAGS"                    [97] 
                                       - "PKG_LIBS"                        [98] 
[97] "POWERSHELL_DISTRIBUTION_CHANNEL" | "POWERSHELL_DISTRIBUTION_CHANNEL" [99] 
[98] "PWD"                             | "PWD"                             [100]
[99] "RENV_CONFIG_REPOS_OVERRIDE"      | "RENV_CONFIG_REPOS_OVERRIDE"      [101]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
      names(before[[4]])        | names(after[[4]])              
[153] "TESTTHAT"                | "TESTTHAT"                [155]
[154] "TZ"                      | "TZ"                      [156]
[155] "USER"                    | "USER"                    [157]
                                - "USE_CXX17"               [158]
[156] "VCPKG_INSTALLATION_ROOT" | "VCPKG_INSTALLATION_ROOT" [159]
[157] "XDG_CONFIG_HOME"         | "XDG_CONFIG_HOME"         [160]
[158] "XDG_RUNTIME_DIR"         | "XDG_RUNTIME_DIR"         [161]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
before[[4]][94:99] vs after[[4]][94:101]
  PIPX_BIN_DIR"/opt/pipx_bin"
  PIPX_HOME"/opt/pipx"
  PKGCACHE_HTTP_VERSION"2"
  PKGLOAD_PARENT_TEMPDIR"/tmp/RtmpQHAqXH"
+ PKG_CPPFLAGS"  -I\"/home/runner/work/_temp/Library/Rcpp/include/\"  -I\"/home/runner/work/_temp/Library/RcppEigen/include/\"  -I\"/home/runner/work/_temp/Library/RcppEigen/include/unsupported\"  -I\"/home/runner/work/_temp/Library/BH/include\" -I\"/home/runner/work/_temp/Library/StanHeaders/include/src/\"  -I\"/home/runner/work/_temp/Library/StanHeaders/include/\"  -I\"/home/runner/work/_temp/Library/RcppParallel/include/\"  -I\"/home/runner/work/_temp/Library/rstan/include\" -DEIGEN_NO_DEBUG  -DBOOST_DISABLE_ASSERTS  -DBOOST_PENDING_INTEGER_LOG2_HPP  -DSTAN_THREADS  -DUSE_STANC3 -DSTRICT_R_HEADERS  -DBOOST_PHOENIX_NO_VARIADIC_EXPRESSION  -D_HAS_AUTO_PTR_ETC=0  -include '/home/runner/work/_temp/Library/StanHeaders/include/stan/math/prim/fun/Eigen.hpp'  -D_REENTRANT -DRCPP_PARALLEL_USE_TBB=1 "
+ PKG_LIBS" '/home/runner/work/_temp/Library/rstan/lib//libStanServices.a' -L'/home/runner/work/_temp/Library/StanHeaders/lib/' -lStanHeaders -L'/home/runner/work/_temp/Library/RcppParallel/lib/' -ltbb "
  POWERSHELL_DISTRIBUTION_CHANNEL"GitHub-Actions-ubuntu22"
  PWD"/home/runner/work/report/report"
  RENV_CONFIG_REPOS_OVERRIDE"https://packagemanager.posit.co/cran/__linux__/jammy/latest"
      before[[4]]              | after[[4]]                    
[153] "true"                   | "true"                   [155]
[154] "UTC"                    | "UTC"                    [156]
[155] "runner"                 | "runner"                 [157]
                               - "1"                      [158]
[156] "/usr/local/share/vcpkg" | "/usr/local/share/vcpkg" [159]
[157] "/home/runner/.config"   | "/home/runner/.config"   [160]
[158] "/run/user/1001"         | "/run/user/1001"         [161]

The brms maintainer suggested that this might have to do with rstan and not brms. Would you have any idea as to how we can fix this on our end, or is this something that needs fixing in rstan or in some of its dependencies?

Start with test-report.brmsfit.R in the report workflow and reproduce the brms::brm call that emits the warning. Compare the reported environment changes, especially PKG_CPPFLAGS, PKG_LIBS, and USE_CXX17, while tracing whether rstan or a dependency introduces them. Done means identifying the responsible component and establishing a test or workflow result without the warning.

Written by the indexing model from the issue text.

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