properly define variables in case they were not set

eng/pipelines/insert.yml

@@ -28,6 +28,13 @@ parameters:
     type: string
     default: ''
 
+# Defined variables that may be overwridden depending on the input parameters.
+variables:
+  - name: Template.ComponentAzdoUri
+    value: ''
+  - name: Template.ComponentProjectName
+    value: ''
+
 steps:
   - checkout: none
 
@@ -37,9 +44,10 @@ steps:
       command: custom
       arguments: 'install RoslynTools.VisualStudioInsertionTool -PreRelease -Source https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json'
 
+  # If we were passed a component build project name, set the corresponding uri and project name so we can retrieve the build.
   - powershell: |
-      Write-Host "##vso[task.setvariable variable=Insertion.ComponentAzdoUri]$($(System.CollectionUri))"
-      Write-Host "##vso[task.setvariable variable=Insertion.ComponentProjectName]$(${{ parameters.componentBuildProjectName }})"
+      Write-Host "##vso[task.setvariable variable=Template.ComponentAzdoUri]$($(System.CollectionUri))"
+      Write-Host "##vso[task.setvariable variable=Template.ComponentProjectName]$(${{ parameters.componentBuildProjectName }})"
     displayName: Set Insertion Variables
     condition: ne('${{ parameters.componentBuildProjectName }}', '')
 
@@ -51,8 +59,8 @@ steps:
         -cherryPick "(default)" `
         -clientId "${{ parameters.clientId }}" `
         -clientSecret "${{ parameters.clientSecret }}" `
-        -componentAzdoUri "$(Insertion.ComponentAzdoUri)" `
-        -componentProjectName "$(Insertion.ComponentProjectName)" `
+        -componentAzdoUri "$(Template.ComponentAzdoUri)" `
+        -componentProjectName "$(Template.ComponentProjectName)" `
         -componentName "Roslyn" `
         -componentGitHubRepoName "dotnet/roslyn" `
         -componentBranchName "${{ parameters.componentBranchName }}" `