Source-build template default pool fix; clean up parameters (dotnet#6790)

* Rename runSourceBuild -> enableSourceBuild

The 'enable*' properties are more common.

* Set up default container host pool

* Use default platform iff 0 platforms passed

Author: dagood

eng/common/templates/job/source-build.yml

@@ -28,6 +28,11 @@ parameters:
   #   container and pool.
   platform: {}
 
+  # The default VM host AzDO pool. This should be capable of running Docker containers: almost all
+  # source-build builds run in Docker, including the default managed platform.
+  defaultContainerHostPool:
+    vmImage: ubuntu-20.04
+
 jobs:
 - job: ${{ parameters.jobNamePrefix }}_${{ parameters.platform.name }}
   displayName: Source-Build (${{ parameters.platform.name }})
@@ -37,6 +42,9 @@ jobs:
 
   ${{ if ne(parameters.platform.container, '') }}:
     container: ${{ parameters.platform.container }}
+
+  ${{ if eq(parameters.platform.pool, '') }}:
+    pool: ${{ parameters.defaultContainerHostPool }}
   ${{ if ne(parameters.platform.pool, '') }}:
     pool: ${{ parameters.platform.pool }}
 

eng/common/templates/jobs/jobs.yml

@@ -7,7 +7,14 @@ parameters:
 
   # Optional: Enable publishing using release pipelines
   enablePublishUsingPipelines: false
-  
+
+  # Optional: Enable running the source-build jobs to build repo from source
+  enableSourceBuild: false
+
+  # Optional: Parameters for source-build template.
+  #           See /eng/common/templates/jobs/source-build.yml for options
+  sourceBuildParameters: []
+
   graphFileGeneration:
     # Optional: Enable generating the graph files at the end of the build
     enabled: false
@@ -24,13 +31,6 @@ parameters:
   #           if 'true', the build won't run any of the internal only steps, even if it is running in non-public projects.
   runAsPublic: false
 
-  # Optional: Enable running the source-build jobs to build repo from source
-  runSourceBuild: false
-
-  # Optional: Parameters for source-build template.
-  #           See /eng/common/templates/jobs/source-build.yml for options
-  sourceBuildParameters: []
-
   enableSourceIndex: false
   sourceIndexParams: {}
 
@@ -53,7 +53,7 @@ jobs:
 
       name: ${{ job.job }}
 
-- ${{ if eq(parameters.runSourceBuild, true) }}:
+- ${{ if eq(parameters.enableSourceBuild, true) }}:
   - template: /eng/common/templates/jobs/source-build.yml
     parameters:
       allCompletedJobId: Source_Build_Complete
@@ -80,7 +80,7 @@ jobs:
         - ${{ if eq(parameters.publishBuildAssetsDependsOn, '') }}:
           - ${{ each job in parameters.jobs }}:
             - ${{ job.job }}
-        - ${{ if eq(parameters.runSourceBuild, true) }}:
+        - ${{ if eq(parameters.enableSourceBuild, true) }}:
           - Source_Build_Complete
         pool:
           vmImage: vs2017-win2016

eng/common/templates/jobs/source-build.yml

@@ -11,16 +11,14 @@ parameters:
   # See /eng/common/templates/job/source-build.yml
   jobNamePrefix: 'Source_Build'
 
-  # If changed to true, causes this template to include the default platform for a managed-only
-  # repo. The exact Docker image used for this build will be provided by Arcade. This has some risk,
-  # but since the repo is supposed to be managed-only, the risk should be very low.
-  includeDefaultManagedPlatform: false
+  # This is the default platform provided by Arcade, intended for use by a managed-only repo.
   defaultManagedPlatform:
     name: 'Managed'
     container: 'mcr.microsoft.com/dotnet-buildtools/prereqs:centos-7-3e800f1-20190501005343'
 
   # Defines the platforms on which to run build jobs. One job is created for each platform, and the
-  # object in this array is sent to the job template as 'platform'.
+  # object in this array is sent to the job template as 'platform'. If no platforms are specified,
+  # one job runs on 'defaultManagedPlatform'.
   platforms: []
 
 jobs:
@@ -32,7 +30,7 @@ jobs:
     dependsOn:
     - ${{ each platform in parameters.platforms }}:
       - ${{ parameters.jobNamePrefix }}_${{ platform.name }}
-    - ${{ if eq(parameters.includeDefaultManagedPlatform, true) }}:
+    - ${{ if eq(length(parameters.platforms), 0) }}:
       - ${{ parameters.jobNamePrefix }}_${{ parameters.defaultManagedPlatform.name }}
 
 - ${{ each platform in parameters.platforms }}:
@@ -41,7 +39,7 @@ jobs:
       jobNamePrefix: ${{ parameters.jobNamePrefix }}
       platform: ${{ platform }}
 
-- ${{ if eq(parameters.includeDefaultManagedPlatform, true) }}:
+- ${{ if eq(length(parameters.platforms), 0) }}:
   - template: /eng/common/templates/job/source-build.yml
     parameters:
       jobNamePrefix: ${{ parameters.jobNamePrefix }}