SqlTraceFlag: Fix for #1688

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- SqlTraceFlag
+  - Fixed $nul reference error when no actual traceflags are present.
+    Added two arrays to prevent a $nul reference at compare-object.
+    ([issue #1688](https://github.com/dsccommunity/SqlServerDsc/issues/1688)).
 - SqlServerDsc
   - Removed a left-over comment in the file `analyzersettings.psd1`.
 

source/DSCResources/DSC_SqlTraceFlag/DSC_SqlTraceFlag.psm1

@@ -176,13 +176,19 @@ function Set-TargetResource
 
     if ($PSBoundParameters.ContainsKey('TraceFlags'))
     {
-        $wishTraceFlags.AddRange($TraceFlags)
+        if ($null -ne $TraceFlags)
+        {
+            $wishTraceFlags.AddRange($TraceFlags)
+        }
     }
     else
     {
         $getTargetResourceResult = Get-TargetResource @getTargetResourceParameters
 
-        $wishTraceFlags.AddRange($getTargetResourceResult.TraceFlags)
+        if ($null -ne $getTargetResourceResult.TraceFlags)
+        {
+            $wishTraceFlags.AddRange($getTargetResourceResult.TraceFlags)
+        }
 
         if ($PSBoundParameters.ContainsKey('TraceFlagsToInclude'))
         {
@@ -371,8 +377,22 @@ function Test-TargetResource
         }
         else
         {
+            $reference = [System.Collections.ArrayList]::new()
+
+            if ($null -ne $getTargetResourceResult.TraceFlags)
+            {
+                $reference.AddRange($getTargetResourceResult.TraceFlags)
+            }
+
+            $difference = [System.Collections.ArrayList]::new()
+
+            if ($null -ne $TraceFlags)
+            {
+                $difference.AddRange($TraceFlags)
+            }
+
             # Compare $TraceFlags to the Actual TraceFlags ($getTargetResourceResult.TraceFlags) to see if they contain the same values.
-            $nullIfTheSame = Compare-Object -ReferenceObject $getTargetResourceResult.TraceFlags -DifferenceObject $TraceFlags
+            $nullIfTheSame = Compare-Object -ReferenceObject $reference -DifferenceObject $difference
             if ($null -ne $nullIfTheSame)
             {
                 Write-Verbose -Message (

tests/Unit/DSC_SqlTraceFlag.Tests.ps1

@@ -357,7 +357,7 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 Mock -CommandName Import-SQLPSModule
             }
 
-            Context 'When the system is not in the desired state and TraceFlags is empty' {
+            Context 'When the system is not in the desired state and TraceFlags is empty with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -375,7 +375,7 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 }
             }
 
-            Context 'When the system is in the desired state and TraceFlags is empty' {
+            Context 'When the system is in the desired state and TraceFlags is empty without existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockInst00Parameters
                     $testParameters += @{
@@ -393,7 +393,7 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 }
             }
 
-            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlags does not match the actual TraceFlags' {
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlags does not match the actual TraceFlags with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -411,7 +411,25 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 }
             }
 
-            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToInclude are not in the actual TraceFlags' {
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlags does not match the actual TraceFlags without existing traceflag' {
+                BeforeAll {
+                    $testParameters = $mockInst00Parameters
+                    $testParameters += @{
+                        TraceFlags = '3228'
+                    }
+                }
+
+                It 'Should return false when Traceflags do not match the actual TraceFlags' {
+                    $result = Test-TargetResource @testParameters
+                    $result | Should -BeFalse
+                }
+
+                It 'Should be executed once' {
+                    Assert-MockCalled -CommandName New-Object -Exactly -Times 1 -Scope Context
+                }
+            }
+
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToInclude are not in the actual TraceFlags with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -429,6 +447,24 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 }
             }
 
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToInclude are not in the actual TraceFlags without existing traceflag' {
+                BeforeAll {
+                    $testParameters = $mockInst00Parameters
+                    $testParameters += @{
+                        TraceFlagsToInclude = '3228'
+                    }
+                }
+
+                It 'Should return false when TraceflagsToInclude are not in the actual TraceFlags' {
+                    $result = Test-TargetResource @testParameters
+                    $result | Should -BeFalse
+                }
+
+                It 'Should be executed once' {
+                    Assert-MockCalled -CommandName New-Object -Exactly -Times 1 -Scope Context
+                }
+            }
+
             Context 'When the system is in the desired state and ensure is set to Present and `$TraceFlagsToInclude are in the actual TraceFlags' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
@@ -465,7 +501,7 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 }
             }
 
-            Context 'When the system is in the desired state and ensure is set to Present and `$TraceFlagsToExclude are not in the actual TraceFlags' {
+            Context 'When the system is in the desired state and ensure is set to Present and `$TraceFlagsToExclude are not in the actual TraceFlags with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -483,6 +519,23 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 }
             }
 
+            Context 'When the system is in the desired state and ensure is set to Present and `$TraceFlagsToExclude are not in the actual TraceFlags without existing traceflag' {
+                BeforeAll {
+                    $testParameters = $mockInst00Parameters
+                    $testParameters += @{
+                        TraceFlagsToExclude = '3228'
+                    }
+                }
+
+                It 'Should return true when TraceflagsToExclude are not in the actual TraceFlags' {
+                    $result = Test-TargetResource @testParameters
+                    $result | Should -BeTrue
+                }
+
+                It 'Should be executed once' {
+                    Assert-MockCalled -CommandName New-Object -Exactly -Times 1 -Scope Context
+                }
+            }
 
             Context 'When both the parameters TraceFlags and TraceFlagsToInclude are assigned a value.' {
                 BeforeAll {
@@ -651,7 +704,7 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
                 Mock -CommandName Import-SQLPSModule
             }
 
-            Context 'When the system is not in the desired state and ensure is set to Absent' {
+            Context 'When the system is not in the desired state and ensure is set to Absent with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -670,10 +723,30 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf
 
                     Assert-MockCalled -CommandName New-Object -Exactly -Times 1 -Scope It
                 }
+            }
 
+            Context 'When the system is not in the desired state and ensure is set to Absent without existing traceflag' {
+                BeforeAll {
+                    $testParameters = $mockInst00Parameters
+                    $testParameters += @{
+                        TraceFlags = '3228'
+                    }
+                }
+
+                It 'Should not throw when calling the alter method' {
+                    { Set-TargetResource @testParameters } | Should -Not -Throw
+                    $script:mockMethodAlterRan | Should -BeTrue -Because 'Alter should run'
+                    $script:mockMethodAlterValue | Should -Be @"
+-dC:\Program Files\Microsoft SQL Server\MSSQL15.INST00\MSSQL\DATA\master.mdf;-eC:\Program Files\Microsoft SQL 
+Server\MSSQL15.INST00\MSSQL\Log\ERRORLOG;-lC:\Program Files\Microsoft SQL 
+Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf;-T3228
+"@ -Because 'Alter must change the value correct'
+
+                    Assert-MockCalled -CommandName New-Object -Exactly -Times 1 -Scope It
+                }
             }
 
-            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlags does not match the actual TraceFlags' {
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlags does not match the actual TraceFlags with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -694,7 +767,28 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf;-T3228
                 }
             }
 
-            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToInclude is not in TraceFlags' {
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlags does not match the actual TraceFlags without existing traceflag' {
+                BeforeAll {
+                    $testParameters = $mockInst00Parameters
+                    $testParameters += @{
+                        TraceFlags = '3228'
+                    }
+                }
+
+                It 'Should not throw when calling the alter method' {
+                    { Set-TargetResource @testParameters } | Should -Not -Throw
+                    $script:mockMethodAlterRan | Should -BeTrue -Because 'Alter should run'
+                    $script:mockMethodAlterValue | Should -Be @"
+-dC:\Program Files\Microsoft SQL Server\MSSQL15.INST00\MSSQL\DATA\master.mdf;-eC:\Program Files\Microsoft SQL 
+Server\MSSQL15.INST00\MSSQL\Log\ERRORLOG;-lC:\Program Files\Microsoft SQL 
+Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf;-T3228
+"@ -Because 'Alter must change the value correct'
+
+                    Assert-MockCalled -CommandName New-Object -Exactly -Times 1 -Scope It
+                }
+            }
+
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToInclude is not in TraceFlags with existing traceflag' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1
                     $testParameters += @{
@@ -715,6 +809,27 @@ Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf;-T3226;-T1802;-T3228
                 }
             }
 
+            Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToInclude is not in TraceFlags without existing traceflag' {
+                BeforeAll {
+                    $testParameters = $mockInst00Parameters
+                    $testParameters += @{
+                        TraceFlagsToInclude = '3228'
+                    }
+                }
+
+                It 'Should not throw when calling the alter method' {
+                    { Set-TargetResource @testParameters } | Should -Not -Throw
+                    $script:mockMethodAlterRan | Should -BeTrue
+                    $script:mockMethodAlterValue | Should -Be @"
+-dC:\Program Files\Microsoft SQL Server\MSSQL15.INST00\MSSQL\DATA\master.mdf;-eC:\Program Files\Microsoft SQL 
+Server\MSSQL15.INST00\MSSQL\Log\ERRORLOG;-lC:\Program Files\Microsoft SQL 
+Server\MSSQL15.INST00\MSSQL\DATA\mastlog.ldf;-T3228
+"@
+
+                    Assert-MockCalled -CommandName New-Object -Exactly -Times 2 -Scope It
+                }
+            }
+
             Context 'When the system is not in the desired state and ensure is set to Present and `$TraceFlagsToExclude is in TraceFlags' {
                 BeforeAll {
                     $testParameters = $mockDefaultParameters1