Handle empty preference object when updating settings (#10)

* fix for #8
* added tests for Set-BloggerConfig

Author: bryanbcook

src/public/Set-BloggerConfig.ps1

@@ -2,30 +2,34 @@ Function Set-BloggerConfig
 {
   [CmdletBinding()]
   Param(
+    [Parameter(Mandatory=$true)]
     [ValidateSet("BlogId","PandocAdditionalArgs","PandocHtmlFormat","PandocMarkdownFormat")]
     [string]$Name,
 
+    [Parameter(Mandatory=$true)]
+    [AllowEmptyString()]
     [string]$Value
   )
-
-  $userPreferences = @{}
+  $userPreferences = [pscustomobject]@{}
 
   if (Test-Path $BloggerSession.UserPreferences)
   {
-    Write-Verbose "Loading preferences from $($BloggerSession.UserPreferences)"
-    $userPreferences = Get-Content $BloggerSession.UserPreferences | ConvertFrom-Json
+    Write-Verbose "Set-BloggerConfig: Loading preferences from $($BloggerSession.UserPreferences)"
+    $userPreferences = [pscustomobject](Get-Content $BloggerSession.UserPreferences -Raw | ConvertFrom-Json)
+    $userPreferences | Out-String | Write-Verbose
   }
 
-  if ($userPreferences.PsObject.Properties.Name -notcontains $Name)
+  if (@($userPreferences.PsObject.Properties).Count -eq 0 -or $Name -notin $userPreferences.PsObject.Properties.Name)
   {
-    Write-Verbose "Adding Property $Name"
+    Write-Verbose "Set-BloggerConfig: Adding Property $Name"
     $userPreferences | Add-Member -Name $Name -Value $Value -MemberType NoteProperty
   }
   else {
-    Write-Verbose "Updating Propery $Name"
+    Write-Verbose "Set-BloggerConfig: Updating Propery $Name"
     $userPreferences.$Name = $Value
   }  
 
+  Write-Verbose "Set-BloggerConfig: Saving preferences to $($BloggerSession.UserPreferences)"
   Set-Content -Path $BloggerSession.UserPreferences -Value ($userPreferences | ConvertTo-Json)
   $BloggerSession.$Name = $Value
 }

src/tests/Set-BloggerConfig.Tests.ps1

@@ -0,0 +1,41 @@
+
+Describe "Set-BloggerConfig" {
+  BeforeEach {
+    Import-Module $PSScriptRoot\..\PSBlogger.psm1 -Force
+    InModuleScope "PSBlogger" {
+      $BloggerSession = [pscustomobject]@{
+        BlogId = $null
+        UserPreferences = "TestDrive:\UserPreferences.json"
+      }
+    }    
+  }
+
+  It "Should persist new value to <UserPreference> to BloggerSession.UserPreferences" -TestCases @(
+    @{ UserPreference="BlogId"; UserPreferenceValue="12345" }
+  ) {
+    # act
+    Set-BloggerConfig -Name $UserPreference -Value $UserPreferenceValue -ErrorAction Stop
+
+    # assert
+    InModuleScope "PSBlogger" {
+      $userPreferences = Get-Content $BloggerSession.UserPreferences -Raw | ConvertFrom-Json
+      $userPreferences.$UserPreference | Should -Be $UserPreferenceValue
+    } -Parameters @{ UserPreference=$UserPreference; UserPreferenceValue=$UserPreferenceValue }
+  }
+
+  It "Should persist new value to <UserPreference> to empty BloggerSession.UserPreferences file" -TestCases @(
+    @{ UserPreference="BlogId"; UserPreferenceValue="12345" }
+  ) {
+    # arrange: empty file
+    Set-Content TestDrive:\UserPreferences.json -Value "{}"
+
+    # act
+    Set-BloggerConfig -Name $UserPreference -Value $UserPreferenceValue
+
+    # assert
+    InModuleScope "PSBlogger" {
+      $userPreferences = Get-Content $BloggerSession.UserPreferences -Raw | ConvertFrom-Json
+      $userPreferences.$UserPreference | Should -Be $UserPreferenceValue
+    } -Parameters @{ UserPreference=$UserPreference; UserPreferenceValue=$UserPreferenceValue }
+  }
+}