Refactor PowerShell installation: improve comments for clarity; standardize version resolution logic across platforms.

Author: MariusStorhaug

action.yml

@@ -1,6 +1,6 @@
 name: Install PowerShell
 description: >
-  Install a specific version —or the latest stable version— of PowerShell Core
+  Install a specific version —or the latest stable version— of PowerShell Core
   on any GitHub runner (Linux, macOS, Windows).
   Skips the install if the requested version is already present.
 author: PSModule
@@ -15,7 +15,7 @@ inputs:
       Use `latest`, `null`, leave it **empty**, or omit the input entirely
       to grab the newest stable release automatically.
     required: false
-    default: ''
+    default: '' # Empty string → newest release
 
 runs:
   using: composite
@@ -28,15 +28,17 @@ runs:
       run: |
         set -e
 
-        # Resolve empty / 'null' / 'latest' to a concrete version number
-        lower_req="$(printf '%s' "$REQUESTED_VERSION" | tr '[:upper:]' '[:lower:]')"
-        if [[ -z "$REQUESTED_VERSION" || "$lower_req" == "latest" || "$lower_req" == "null" ]]; then
-          REQUESTED_VERSION=$(
-            curl -s https://api.github.com/repos/PowerShell/PowerShell/releases/latest \
-              | grep -oP '"tag_name":\s*"\K([^"]+)' | sed 's/^v//'
-          )
-          echo "Latest stable PowerShell release detected: $REQUESTED_VERSION"
-        fi
+        # Resolve "" / null / latest  →  concrete latest version (Bash‑3 safe)
+        case "${REQUESTED_VERSION:-}" in
+            ""|[Ll][Aa][Tt][Ee][Ss][Tt]|[Nn][Uu][Ll][Ll]|~)
+                REQUESTED_VERSION=$(
+                  curl -s https://api.github.com/repos/PowerShell/PowerShell/releases/latest |
+                    grep '"tag_name"' | head -n1 |
+                    sed -E 's/.*"v?([^"]+)".*/\1/'
+                )
+                echo "Latest stable PowerShell release detected: $REQUESTED_VERSION"
+                ;;
+        esac
 
         DETECTED_VERSION=$(pwsh -NoLogo -NoProfile -Command '$PSVersionTable.PSVersion.ToString()' 2>/dev/null || true)
         if [[ "$DETECTED_VERSION" == "$REQUESTED_VERSION" ]]; then
@@ -81,15 +83,16 @@ runs:
       run: |
         set -e
 
+        # Resolve "" / null / latest  →  concrete latest version (Bash‑3 safe)
         case "${REQUESTED_VERSION:-}" in
-          "" | [Ll][Aa][Tt][Ee][Ss][Tt] | [Nn][Uu][Ll][Ll])
-            REQUESTED_VERSION=$(
-              curl -s https://api.github.com/repos/PowerShell/PowerShell/releases/latest |
-                grep '"tag_name"' | head -n1 |
-                sed -E 's/.*"v?([^"]+)".*/\1/'
-            )
-            echo "Latest stable PowerShell release detected: $REQUESTED_VERSION"
-            ;;
+            ""|[Ll][Aa][Tt][Ee][Ss][Tt]|[Nn][Uu][Ll][Ll]|~)
+                REQUESTED_VERSION=$(
+                  curl -s https://api.github.com/repos/PowerShell/PowerShell/releases/latest |
+                    grep '"tag_name"' | head -n1 |
+                    sed -E 's/.*"v?([^"]+)".*/\1/'
+                )
+                echo "Latest stable PowerShell release detected: $REQUESTED_VERSION"
+                ;;
         esac
 
         DETECTED_VERSION=$(pwsh -NoLogo -NoProfile -Command '$PSVersionTable.PSVersion.ToString()' 2>/dev/null || true)
@@ -118,10 +121,10 @@ runs:
       env:
         REQUESTED_VERSION: ${{ inputs.Version }}
       run: |
-        # Resolve empty / 'null' / 'latest' to a concrete version number
+        # Resolve "" / null / latest  →  concrete latest version
         $req = $env:REQUESTED_VERSION
         if ([string]::IsNullOrWhiteSpace($req) -or
-            ($req.Trim().ToLower() -in @('latest','null'))) {
+            $req.Trim().ToLower() -in @('latest','null','~')) {
 
             $latest = (Invoke-RestMethod -Uri 'https://api.github.com/repos/PowerShell/PowerShell/releases/latest').tag_name.TrimStart('v')
             Write-Host "Latest stable PowerShell release detected: $latest"