ci: add yarn cache for material-unit tests job (#29378)

PR Close #29378

.circleci/config.yml

@@ -563,7 +563,24 @@ jobs:
     steps:
       - *attach_workspace
       - *init_environment
-      - run: ./scripts/ci/run_angular_material_unit_tests.sh
+      - run:
+          name: "Determining SHA of Material Ivy branch"
+          command: git ls-remote ${MATERIAL_REPO_URL} ${MATERIAL_REPO_BRANCH} | cut -f1 > material_repo_sha
+      - run:
+          name: "Cloning Material repository"
+          command: ./scripts/ci/clone_angular_material_repo.sh
+      - restore_cache:
+          keys:
+            - v1-angular-material-{{ checksum "material_repo_sha" }}
+            - v1-angular-material-
+      - run:
+          name: "Running Material unit tests"
+          command: ./scripts/ci/run_angular_material_unit_tests.sh
+      - save_cache:
+          key: v1-angular-material-{{ checksum "material_repo_sha" }}
+          paths:
+            # Needs to be hardcoded because environment variables are not interpolated here.
+            - "/tmp/material2/node_modules"
 
 workflows:
   version: 2

.circleci/env.sh

@@ -62,6 +62,15 @@ setPublicVar SAUCE_TUNNEL_IDENTIFIER "angular-${CIRCLE_BUILD_NUM}-${CIRCLE_NODE_
 # acquire CircleCI instances for too long if sauceconnect failed, we need a connect timeout.
 setPublicVar SAUCE_READY_FILE_TIMEOUT 120
 
+####################################################################################################
+# Define environment variables for the Angular Material unit tests job.
+####################################################################################################
+# We specifically use a directory within "/tmp" here because we want the cloned repo to be
+# completely isolated from angular/angular in order to avoid any bad interactions between
+# their separate build setups.
+setPublicVar MATERIAL_REPO_TMP_DIR "/tmp/material2"
+setPublicVar MATERIAL_REPO_URL "https://github.com/angular/material2.git"
+setPublicVar MATERIAL_REPO_BRANCH "ivy-2019"
 
 # Source `$BASH_ENV` to make the variables available immediately.
 source $BASH_ENV;