ci: compute Windows Bazel PATH in setup action

.bazelrc

@@ -29,10 +29,6 @@ common:linux --test_env=PATH=/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
 common:macos --test_env=PATH=/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
 
 # Pass through some env vars Windows needs to use powershell?
-# CI overrides PATH in `.github/scripts/run-bazel-ci.sh` with a cache-stable
-# allow-list so unrelated GitHub Windows image tool updates do not invalidate
-# BuildBuddy action/test cache entries.
-common:windows --test_env=PATH
 common:windows --test_env=SYSTEMROOT
 common:windows --test_env=COMSPEC
 common:windows --test_env=WINDIR

.github/actions/setup-bazel-ci/action.yml

@@ -122,6 +122,77 @@ runs:
           }
         }
 
+    - name: Compute cache-stable Windows Bazel PATH
+      if: runner.os == 'Windows'
+      shell: pwsh
+      run: |
+        # Bazel action/test cache keys include PATH when it is forwarded into the
+        # execution environment. Filter the runner PATH down to the tool
+        # locations these Windows Bazel jobs actually need so hosted-image churn
+        # such as Maven updates does not invalidate otherwise reusable entries.
+        $stablePathEntries = New-Object System.Collections.Generic.List[string]
+        $seenEntries = [System.Collections.Generic.HashSet[string]]::new([System.StringComparer]::OrdinalIgnoreCase)
+        $windowsAppsPath = Join-Path $env:LOCALAPPDATA 'Microsoft\WindowsApps'
+        $windowsDir = if ($env:WINDIR) { $env:WINDIR } else { $env:SystemRoot }
+
+        function Add-StablePathEntry {
+          param([string]$PathEntry)
+
+          if ([string]::IsNullOrWhiteSpace($PathEntry)) {
+            return
+          }
+
+          if ($seenEntries.Add($PathEntry)) {
+            [void]$stablePathEntries.Add($PathEntry)
+          }
+        }
+
+        foreach ($pathEntry in ($env:PATH -split ';')) {
+          if ([string]::IsNullOrWhiteSpace($pathEntry)) {
+            continue
+          }
+
+          if (
+            $pathEntry -like '*Microsoft Visual Studio*' -or
+            $pathEntry -like '*Windows Kits*' -or
+            $pathEntry -like '*Microsoft SDKs*' -or
+            $pathEntry -like 'C:\Program Files\Git\*' -or
+            $pathEntry -like 'C:\Program Files\PowerShell\*' -or
+            $pathEntry -like 'C:\hostedtoolcache\windows\node\*' -or
+            $pathEntry -eq 'D:\a\_temp\install-dotslash\bin' -or
+            ($windowsDir -and ($pathEntry -eq $windowsDir -or $pathEntry -like "${windowsDir}\*")) -or
+            ($windowsAppsPath -and $pathEntry -eq $windowsAppsPath)
+          ) {
+            Add-StablePathEntry $pathEntry
+          }
+        }
+
+        $gitCommand = Get-Command git -ErrorAction SilentlyContinue
+        if ($gitCommand) {
+          Add-StablePathEntry (Split-Path $gitCommand.Source -Parent)
+        }
+
+        $nodeCommand = Get-Command node -ErrorAction SilentlyContinue
+        if ($nodeCommand) {
+          Add-StablePathEntry (Split-Path $nodeCommand.Source -Parent)
+        }
+
+        $pwshCommand = Get-Command pwsh -ErrorAction SilentlyContinue
+        if ($pwshCommand) {
+          Add-StablePathEntry (Split-Path $pwshCommand.Source -Parent)
+        }
+
+        if (Test-Path $windowsAppsPath) {
+          Add-StablePathEntry $windowsAppsPath
+        }
+
+        if ($stablePathEntries.Count -eq 0) {
+          throw 'Failed to derive cache-stable Windows PATH.'
+        }
+
+        $stablePath = $stablePathEntries -join ';'
+        "CODEX_BAZEL_WINDOWS_PATH=$stablePath" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+
     - name: Enable Git long paths (Windows)
       if: runner.os == 'Windows'
       shell: pwsh

.github/scripts/run-bazel-ci.sh

@@ -323,46 +323,15 @@ if [[ "${RUNNER_OS:-}" == "Windows" ]]; then
     fi
   done
 
-  # The GitHub Windows image puts many unrelated versioned tools on PATH. Those
-  # entries are still part of Bazel action/test keys when PATH is forwarded, so
-  # image churn such as Maven minor-version updates can invalidate otherwise
-  # reusable cache entries. Keep only the PATH segments Bazel actions/tests need.
-  windows_cache_stable_path_entries=()
-  if [[ -n "${PATH:-}" ]]; then
-    windows_path="${PATH}"
-    if command -v cygpath >/dev/null 2>&1; then
-      windows_path="$(cygpath -w -p "${PATH}")"
-    fi
-
-    IFS=';' read -r -a windows_path_entries <<< "${windows_path}"
-    for path_entry in "${windows_path_entries[@]}"; do
-      case "${path_entry}" in
-        *'Microsoft Visual Studio'* | \
-          *'Windows Kits'* | \
-          *'Microsoft SDKs'* | \
-          'C:\Program Files\Git\'* | \
-          'C:\Program Files\PowerShell\'* | \
-          'C:\Users\runneradmin\AppData\Local\Microsoft\WindowsApps' | \
-          'C:\hostedtoolcache\windows\node\'* | \
-          'C:\Windows' | \
-          'C:\Windows\'* | \
-          'D:\a\_temp\install-dotslash\bin')
-          windows_cache_stable_path_entries+=("${path_entry}")
-          ;;
-      esac
-    done
-  fi
-
-  if (( ${#windows_cache_stable_path_entries[@]} == 0 )); then
-    echo "Failed to derive cache-stable Windows PATH from runner PATH." >&2
+  if [[ -z "${CODEX_BAZEL_WINDOWS_PATH:-}" ]]; then
+    echo "CODEX_BAZEL_WINDOWS_PATH must be set for Windows Bazel CI." >&2
     exit 1
   fi
 
-  stable_windows_path="$(IFS=';'; printf '%s' "${windows_cache_stable_path_entries[*]}")"
   post_config_bazel_args+=(
-    "--action_env=PATH=${stable_windows_path}"
-    "--host_action_env=PATH=${stable_windows_path}"
-    "--test_env=PATH=${stable_windows_path}"
+    "--action_env=PATH=${CODEX_BAZEL_WINDOWS_PATH}"
+    "--host_action_env=PATH=${CODEX_BAZEL_WINDOWS_PATH}"
+    "--test_env=PATH=${CODEX_BAZEL_WINDOWS_PATH}"
   )
 fi