Merge from vscode 8e0f348413f4f616c23a88ae30030efa85811973 (#6381)

* Merge from vscode 8e0f348413f4f616c23a88ae30030efa85811973

* disable strict null check

build/azure-pipelines/linux/continuous-build-linux.yml

@@ -10,6 +10,11 @@ steps:
 - task: NodeTool@0
   inputs:
     versionSpec: "10.15.1"
+- task: 1ESLighthouseEng.PipelineArtifactCaching.RestoreCacheV1.RestoreCache@1
+  inputs:
+    keyfile: '.yarnrc, remote/.yarnrc, **/yarn.lock, !**/node_modules/**/yarn.lock, !**/.*/**/yarn.lock'
+    targetfolder: '**/node_modules, !**/node_modules/**/node_modules'
+    vstsFeed: '$(ArtifactFeed)'
 - task: geeklearningio.gl-vsts-tasks-yarn.yarn-installer-task.YarnInstaller@2
   inputs:
     versionSpec: "1.10.1"
@@ -20,15 +25,15 @@ steps:
 #     vstsFeed: '$(ArtifactFeed)'
 #   condition: eq(variables['System.PullRequest.PullRequestId'], '')
 - script: |
-    yarn
+    yarn --frozen-lockfile
   displayName: Install Dependencies
-  # condition: or(ne(variables['System.PullRequest.PullRequestId'], ''), ne(variables['CacheRestored'], 'true'))
-# - task: 1ESLighthouseEng.PipelineArtifactCaching.SaveCacheV1.SaveCache@1
-#   inputs:
-#     keyfile: '**/yarn.lock, !**/node_modules/**/yarn.lock, !**/.*/**/yarn.lock'
-#     targetfolder: '**/node_modules, !**/node_modules/**/node_modules'
-#     vstsFeed: '$(ArtifactFeed)'
-#   condition: and(succeeded(), eq(variables['System.PullRequest.PullRequestId'], ''), ne(variables['CacheRestored'], 'true'))
+  condition: and(succeeded(), ne(variables['CacheRestored'], 'true'))
+- task: 1ESLighthouseEng.PipelineArtifactCaching.SaveCacheV1.SaveCache@1
+  inputs:
+    keyfile: '.yarnrc, remote/.yarnrc, **/yarn.lock, !**/node_modules/**/yarn.lock, !**/.*/**/yarn.lock'
+    targetfolder: '**/node_modules, !**/node_modules/**/node_modules'
+    vstsFeed: '$(ArtifactFeed)'
+  condition: and(succeeded(), ne(variables['CacheRestored'], 'true'))
 - script: |
     yarn gulp electron-x64
   displayName: Download Electron