fix: address all Copilot review comments on PR #16

- Add null/empty checks for prerelease resolution on all 3 platforms
  (Linux jq // empty + bash validation, macOS same, Windows null check)
- Fix prerelease downgrade detection: force uninstall when same base
  version but different prerelease labels (MSI can't handle in-place)
- Fix inconsistent regex escaping: -preview|-rc (not -preview|\-rc)
- Fix StartsWith over-matching in registry filter: use regex with
  delimiter-aware boundary instead of string prefix match
- Extract major version dynamically for install path (not hardcoded 7)
- Add GITHUB_PATH updates for Linux/macOS preview builds
- Add null check in test workflow prerelease resolution

Author: MariusStorhaug

.github/workflows/Action-Test.yml

@@ -53,7 +53,11 @@ jobs:
                   'Authorization' = "Bearer $($env:GITHUB_TOKEN)"
                   'X-GitHub-Api-Version' = '2022-11-28'
                 }
-              $requested = ($releases | Where-Object { $_.prerelease -eq $true } | Select-Object -First 1).tag_name.TrimStart('v')
+              $latestPrerelease = $releases | Where-Object { $_.prerelease -eq $true } | Select-Object -First 1
+              if (-not $latestPrerelease) {
+                  throw "No prerelease releases found for PowerShell/PowerShell."
+              }
+              $requested = $latestPrerelease.tag_name.TrimStart('v')
               Write-Host "Resolved 'prerelease' → $requested"
           }
           # When empty / 'null' / 'latest' → resolve to latest stable release

action.yml

@@ -51,8 +51,12 @@ runs:
                         -H "Authorization: Bearer $GITHUB_TOKEN" \
                         -H "X-GitHub-Api-Version: 2022-11-28" \
                         https://api.github.com/repos/PowerShell/PowerShell/releases |
-                        jq -r '[.[] | select(.prerelease == true)] | .[0].tag_name' | sed 's/^v//'
+                        jq -r '[.[] | select(.prerelease == true)] | (.[0].tag_name // empty)' | sed 's/^v//'
                     )
+                    if [[ -z "$REQUESTED_VERSION" ]]; then
+                        echo "Error: No prerelease PowerShell releases found when resolving latest prerelease."
+                        exit 1
+                    fi
                     echo "Latest prerelease PowerShell version detected: $REQUESTED_VERSION"
                 else
                     REQUESTED_VERSION=$(
@@ -115,6 +119,17 @@ runs:
         fi
         echo "Installation complete. PowerShell [$REQUESTED_VERSION] is now available."
 
+        # For prerelease builds, add the install directory to GITHUB_PATH so subsequent
+        # `shell: pwsh` steps resolve to the version we just installed.
+        if [[ "$REQUESTED_VERSION" == *-* ]]; then
+          MAJOR_VERSION=$(echo "$REQUESTED_VERSION" | cut -d'.' -f1)
+          INSTALL_DIR="/opt/microsoft/powershell/${MAJOR_VERSION}-preview"
+          if [[ -d "$INSTALL_DIR" ]]; then
+            echo "Adding install directory to GITHUB_PATH: $INSTALL_DIR"
+            echo "$INSTALL_DIR" >> "$GITHUB_PATH"
+          fi
+        fi
+
     - name: Install PowerShell (macOS)
       if: runner.os == 'macOS'
       shell: bash
@@ -139,8 +154,12 @@ runs:
                         -H "Authorization: Bearer $GITHUB_TOKEN" \
                         -H "X-GitHub-Api-Version: 2022-11-28" \
                         https://api.github.com/repos/PowerShell/PowerShell/releases |
-                        jq -r '[.[] | select(.prerelease == true)] | .[0].tag_name' | sed 's/^v//'
+                        jq -r '[.[] | select(.prerelease == true)] | (.[0].tag_name // empty)' | sed 's/^v//'
                     )
+                    if [[ -z "$REQUESTED_VERSION" ]]; then
+                        echo "Error: No prerelease PowerShell releases found when resolving latest prerelease."
+                        exit 1
+                    fi
                     echo "Latest prerelease PowerShell version detected: $REQUESTED_VERSION"
                 else
                     REQUESTED_VERSION=$(
@@ -190,6 +209,17 @@ runs:
         sudo installer -pkg "$PKG_NAME" -target /
         echo "Installation complete. PowerShell [$REQUESTED_VERSION] is now available."
 
+        # For prerelease builds, add the install directory to GITHUB_PATH so subsequent
+        # `shell: pwsh` steps resolve to the version we just installed.
+        if [[ "$REQUESTED_VERSION" == *-* ]]; then
+          MAJOR_VERSION=$(echo "$REQUESTED_VERSION" | cut -d'.' -f1)
+          INSTALL_DIR="/usr/local/microsoft/powershell/${MAJOR_VERSION}-preview"
+          if [[ -d "$INSTALL_DIR" ]]; then
+            echo "Adding install directory to GITHUB_PATH: $INSTALL_DIR"
+            echo "$INSTALL_DIR" >> "$GITHUB_PATH"
+          fi
+        fi
+
     - name: Install PowerShell (Windows)
       if: runner.os == 'Windows'
       shell: powershell
@@ -213,7 +243,12 @@ runs:
             }
             if ($env:PRERELEASE -eq 'true') {
                 $releases = Invoke-RestMethod -Uri 'https://api.github.com/repos/PowerShell/PowerShell/releases' -Headers $headers
-                $latest = ($releases | Where-Object { $_.prerelease -eq $true } | Select-Object -First 1).tag_name.TrimStart('v')
+                $latestRelease = $releases | Where-Object { $_.prerelease -eq $true } | Select-Object -First 1
+                if (-not $latestRelease) {
+                    Write-Host "Error: No prerelease PowerShell releases are available from GitHub."
+                    exit 1
+                }
+                $latest = $latestRelease.tag_name.TrimStart('v')
                 Write-Host "Latest prerelease PowerShell version detected: $latest"
             } else {
                 $latest = (Invoke-RestMethod -Uri 'https://api.github.com/repos/PowerShell/PowerShell/releases/latest' -Headers $headers).tag_name.TrimStart('v')
@@ -252,8 +287,10 @@ runs:
               Write-Host "Downgrade detected: $detected → $($env:REQUESTED_VERSION)"
               $isDowngrade = $true
             } elseif ($detectedVersion -eq $requestedVersion -and $detected -ne $env:REQUESTED_VERSION) {
-              # Same base version but different prerelease label, treat as a reinstall
-              Write-Host "Version change detected (same base, different label): $detected → $($env:REQUESTED_VERSION)"
+              # Same base version but different prerelease label — MSI installers cannot
+              # handle cross-prerelease changes in-place, so force uninstall first.
+              Write-Host "Prerelease version change detected (same base, different label): $detected → $($env:REQUESTED_VERSION)"
+              $isDowngrade = $true
             } else {
               Write-Host "Upgrade detected: $detected → $($env:REQUESTED_VERSION)"
             }
@@ -272,14 +309,14 @@ runs:
             'HKLM:\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*'
           )
 
-          $isDetectedPreview = $detected -match '-preview|\-rc'
+          $isDetectedPreview = $detected -match '-preview|-rc'
           $pwshEntries = Get-ItemProperty -Path $regPaths -ErrorAction SilentlyContinue |
             Where-Object {
               $_.Publisher     -eq 'Microsoft Corporation'     -and
               $_.DisplayName   -like 'PowerShell 7*'           -and
               $(if ($isDetectedPreview) { $_.DisplayName -like '*Preview*' } else { $_.DisplayName -notlike '*Preview*' }) -and
               $_.DisplayVersion -and
-              $_.DisplayVersion.StartsWith(($detected -split '-')[0])
+              ($_.DisplayVersion -match "^$([regex]::Escape(($detected -split '-')[0]))([.\-]|$)" -or $_.DisplayVersion -eq ($detected -split '-')[0])
             }
 
           $targetEntry = $pwshEntries | Select-Object -First 1
@@ -337,10 +374,11 @@ runs:
         # resolve to the version we just installed — even for preview builds whose
         # install directory (7-preview) is not on the runner's default PATH.
         $isPrerelease = $env:REQUESTED_VERSION -match '-'
+        $majorVersion = ($env:REQUESTED_VERSION -split '[.\-]')[0]
         $installDir = if ($isPrerelease) {
-            "$env:ProgramFiles\PowerShell\7-preview"
+            "$env:ProgramFiles\PowerShell\$majorVersion-preview"
         } else {
-            "$env:ProgramFiles\PowerShell\7"
+            "$env:ProgramFiles\PowerShell\$majorVersion"
         }
         if (Test-Path $installDir) {
             Write-Host "Adding install directory to GITHUB_PATH: $installDir"