Make CompatibilityCollector able to parse a single version String (#1446)

Co-authored-by: Christoph Bergmeister <christoph.bergmeister@bjss.com>

Author: bergmeister

PSCompatibilityCollector/Microsoft.PowerShell.CrossCompatibility/Common/PowerShellVersion.cs

@@ -88,7 +88,8 @@ public static PowerShellVersion Parse(string versionStr)
 
             if (dotCount == 0)
             {
-                throw new ArgumentException($"Version string '{versionStr}' must contain at least one dot separator");
+                var majorVersion = int.Parse(versionStr);
+                return new PowerShellVersion(majorVersion, -1, -1, label: null);
             }
 
             versionParts[dotCount] = int.Parse(versionStr.Substring(sectionStartOffset, i - sectionStartOffset));

PSCompatibilityCollector/Tests/UtilityApi.Tests.ps1

@@ -101,6 +101,8 @@ Describe "PowerShell version object" {
     Context "Version parsing" {
         BeforeAll {
             $genericVerCases = @(
+                @{ VerStr = '42'; Major = 42; Minor = -1; Patch = -1 }
+                @{ VerStr = '7'; Major = 7; Minor = -1; Patch = -1 }
                 @{ VerStr = '6.1'; Major = 6; Minor = 1; Patch = -1 }
                 @{ VerStr = '5.2.7'; Major = 5; Minor = 2; Patch = 7 }
                 @{ VerStr = '512.2124.71'; Major = 512; Minor = 2124; Patch = 71 }