Skip flutter upgrade for pod linting Cirrus task (flutter#3700)

Author: jmagman

.cirrus.yml

@@ -1,25 +1,37 @@
-root_task_template: &ROOT_TASK_TEMPLATE
-  # Don't run on release tags since it creates O(n^2) tasks where n is the
-  # number of plugins
-  only_if: $CIRRUS_TAG == ''
-  use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true' && $CIRRUS_PR == ''
-  env:
-    INTEGRATION_TEST_PATH: "./packages/integration_test"
-    CHANNEL: "master" # Default to master when not explicitly set by a task.
-    PLUGIN_TOOLS: "dart run ./script/tool/lib/src/main.dart"
-  setup_script:
-    - flutter channel $CHANNEL
-    - flutter upgrade
+# Don't run on release tags since it creates O(n^2) tasks where n is the
+# number of plugins
+only_if: $CIRRUS_TAG == ''
+use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true' && $CIRRUS_PR == ''
+env:
+  INTEGRATION_TEST_PATH: "./packages/integration_test"
+  CHANNEL: "master" # Default to master when not explicitly set by a task.
+  PLUGIN_TOOLS: "dart run ./script/tool/lib/src/main.dart"
+
+tool_setup_template: &TOOL_SETUP_TEMPLATE
+  tool_setup_script:
     - git fetch origin master # To set FETCH_HEAD for "git merge-base" to work
     - cd script/tool
     - pub get
 
+flutter_upgrade_template: &FLUTTER_UPGRADE_TEMPLATE
+  upgrade_flutter_script:
+    - flutter channel $CHANNEL
+    - flutter upgrade
+  << : *TOOL_SETUP_TEMPLATE
+
+macos_template: &MACOS_TEMPLATE
+  # Only one macOS task can run in parallel without credits, so use them for
+  # PRs on macOS.
+  use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true'
+  osx_instance:
+    image: big-sur-xcode-12.3
+  cocoapod_install_script: sudo gem install cocoapods
 
 # Light-workload Linux tasks.
 # These use default machines, with fewer CPUs, to reduce pressure on the
 # concurrency limits.
 task:
-  << : *ROOT_TASK_TEMPLATE
+  << : *FLUTTER_UPGRADE_TEMPLATE
   container:
     dockerfile: .ci/Dockerfile
   matrix:
@@ -109,7 +121,7 @@ task:
 # tasks" block above once web_installers has been updated to support Chrome 89
 # (which is what the current image generated from .ci/Dockerfile has).
 task:
-  << : *ROOT_TASK_TEMPLATE
+  << : *FLUTTER_UPGRADE_TEMPLATE
   container:
     dockerfile: .ci/Dockerfile-LegacyChrome
   matrix:
@@ -134,7 +146,7 @@ task:
 # These use machines with more CPUs and memory, so will reduce parallelization
 # for non-credit runs.
 task:
-  << : *ROOT_TASK_TEMPLATE
+  << : *FLUTTER_UPGRADE_TEMPLATE
   container:
     dockerfile: .ci/Dockerfile
     cpu: 4
@@ -177,24 +189,9 @@ task:
 
 # macOS tasks.
 task:
-  << : *ROOT_TASK_TEMPLATE
-  # Only one macOS task can run in parallel without credits, so use them for
-  # PRs on macOS.
-  use_compute_credits: $CIRRUS_USER_COLLABORATOR == 'true'
-  osx_instance:
-    image: big-sur-xcode-12.3
-  cocoapod_install_script: sudo gem install cocoapods
+  << : *MACOS_TEMPLATE
+  << : *FLUTTER_UPGRADE_TEMPLATE
   matrix:
-    ### Platform-agnostic tasks ###
-    - name: lint_darwin_plugins
-      env:
-        matrix:
-          PLUGIN_SHARDING: "--shardIndex 0 --shardCount 2"
-          PLUGIN_SHARDING: "--shardIndex 1 --shardCount 2"
-      script:
-        # TODO(jmagman): Lint macOS podspecs but skip any that fail library validation.
-        - find . -name "*.podspec" | xargs grep -l "osx" | xargs rm
-        - ./script/incremental_build.sh podspecs
     ### iOS tasks ###
     - name: build_all_plugins_ipa
       env:
@@ -245,3 +242,14 @@ task:
         - flutter config --enable-macos-desktop
         - ./script/incremental_build.sh build-examples --macos --no-ipa
         - ./script/incremental_build.sh drive-examples --macos
+
+task:
+  # Don't use FLUTTER_UPGRADE_TEMPLATE, Flutter tooling not needed.
+  << : *MACOS_TEMPLATE
+  << : *TOOL_SETUP_TEMPLATE
+  matrix:
+    - name: lint_darwin_plugins
+      script:
+        # TODO(jmagman): Lint macOS podspecs but skip any that fail library validation.
+        - find . -name "*.podspec" | xargs grep -l "osx" | xargs rm
+        - ./script/incremental_build.sh podspecs