Create SHA256 of Project List for Cache Key (Azure#30714)

Create SHA256 of Project List for Cache Key

Author: alzimmermsft

eng/pipelines/templates/steps/generate-project-list-and-cache-maven-repository.yml

@@ -20,6 +20,10 @@ parameters:
     default: test
 
 steps:
+  # Create the ProjectList and ProjectListSha256 variables.
+  # The ProjectList is used by subsequent steps and tasks to run CI.
+  # The ProjectListSha256 is used by the cache key, previously the cache key was using ProjectList but it was found
+  # that long cache keys cause caching to fail.
 - pwsh: |
     $artifacts = '${{ convertToJson(parameters.Artifacts) }}' | ConvertFrom-Json
     $additionalModules = '${{ convertToJson(parameters.AdditionalModules) }}' | ConvertFrom-Json
@@ -35,12 +39,18 @@ steps:
 
     Write-Host "ProjectList = $projects"
     Write-Host "##vso[task.setvariable variable=ProjectList;]$projects"
+
+    $sha256 = new-object -TypeName System.Security.Cryptography.SHA256Managed
+    $utf8 = new-object -TypeName System.Text.UTF8Encoding
+
+    $projectListSha256 = [Convert]::ToBase64String($sha256.ComputeHash($utf8.GetBytes($projects)))
+    Write-Host "##vso[task.setvariable variable=ProjectListSha256;]$projectListSha256"
   displayName: Initialize project list variable
 
 - task: Cache@2
   inputs:
   # Note: CacheSalt is only intented to be used in special cases, as a build is queued, to force a cache miss.
   # This would be set as a variable in the UI when the run is queued.
-    key: 'maven | "$(CacheSalt)" | "$(Agent.OS)" | $(Build.SourcesDirectory)/eng/versioning/external_dependencies.txt | "$(ProjectList)" | "${{ parameters.JobType }}" | "$(TestFromSource)"'
+    key: 'maven | "$(CacheSalt)" | "$(Agent.OS)" | $(Build.SourcesDirectory)/eng/versioning/external_dependencies.txt | "$(ProjectListSha256)" | "${{ parameters.JobType }}" | "$(TestFromSource)"'
     path: $(MAVEN_CACHE_FOLDER)
   displayName: Cache Maven local repo