Don't crash on CIM classes with no superclass (#1046)

* Don't crash on CIM classes with no superclass

* ReTrigger CI by using better linq variable name

* add test case

* incorporate PR feedback

* tweak test for linux

* use join-path

Rules/UseIdenticalMandatoryParametersDSC.cs

@@ -258,7 +258,7 @@ private IDictionary<string, string> GetKeys(string fileName)
 
             var cimClass = cimClasses?.FirstOrDefault();
             var cimSuperClassProperties = new HashSet<string>(
-                cimClass?.CimSuperClass.CimClassProperties.Select(p => p.Name) ??
+                cimClass?.CimSuperClass?.CimClassProperties.Select(cimPropertyDeclaration => cimPropertyDeclaration.Name) ??
                 Enumerable.Empty<string>());
 
             return cimClass?

Tests/Rules/UseIdenticalMandatoryParametersForDSC.tests.ps1

@@ -33,4 +33,54 @@ Describe "UseIdenticalMandatoryParametersForDSC" {
             $violations.Count | Should -Be 0
         }
     }
+
+    Context "When a CIM class has no parent" {
+        # regression test for #982 - just check no uncaught exception
+        It "Should find no violations, and throw no exceptions" -skip:($IsLinux -or $IsMacOS) {
+
+            # Arrange test content in testdrive
+            $dscResources = Join-Path -Path "TestDrive:" -ChildPath "DSCResources"
+            $noparentClassDir = Join-Path -Path $dscResources "ClassWithNoParent"
+
+            # need a fake module
+            $fakeModulePath = Join-Path -Path "TestDrive:" -ChildPath "test.psd1"
+            Set-Content -Path $fakeModulePath -Value @"
+@{
+    ModuleVersion = '1.0'
+    GUID = 'f5e6cc2a-5500-4592-bbe2-ef033754b56f'
+    Author = 'test'
+
+    FunctionsToExport = @()
+    CmdletsToExport = @()
+    VariablesToExport = '*'
+    AliasesToExport = @()
+
+    # Private data to pass to the module specified in RootModule/ModuleToProcess. This may also contain a PSData hashtable with additional module metadata used by PowerShell.
+    PrivateData = @{
+        PSData = @{
+        } # End of PSData hashtable
+    } # End of PrivateData hashtable
+}
+"@
+            # and under it a directory called dscresources\something
+            New-Item -ItemType Directory -Path $noParentClassDir
+            $noparentClassFilepath = Join-Path -Path $noParentClassDir -ChildPath 'ClassWithNoParent.psm1'
+            $noparentClassMofFilepath = Join-Path -Path $noParentClassDir -ChildPath 'ClassWithNoParent.schema.mof'
+
+            # containing a .psm1 file and a .schema.mof file with same base name
+            Set-Content -Path $noParentClassFilepath -Value "#requires -Version 4.0 -Modules CimCmdlets" # the file content doesn't much matter
+
+            Set-Content -Path $noParentClassMofFilePath -Value @"
+[ClassVersion("1.0.0")]
+class ClassWithNoParent
+{
+    [Write] Boolean Anonymous;
+};
+"@
+
+            # Act - run scriptanalyzer
+            $violations = Invoke-ScriptAnalyzer -Path $noParentClassFilepath -IncludeRule $ruleName -ErrorAction Stop
+            $violations.Count | Should -Be 0
+        }
+    }
 }