build: ensure dependencies are properly locked

.travis.yml

@@ -56,7 +56,7 @@ before_install:
   - if [[ "$TRAVIS_EVENT_TYPE" == "cron" ]]; then ./scripts/install-angular-snapshot.sh --only-save; fi
 
 install:
-  - yarn install --frozen-lockfile --non-interactive
+  - ./scripts/ci/travis-install.sh
 
 before_script:
   - mkdir -p $LOGS_DIR

scripts/ci/travis-install.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Script that installs the project node module dependencies within Travis. The script also ensures that the cached
+# node modules are in sync with the lock file and also checks that if the lock file is in sync with the
+# project `package.json` file.
+
+# Go to the project root directory
+cd $(dirname $0)/../..
+
+# Yarn's integrity check command throws in the following scenarios:
+#   1) Cached node modules are not in sync with lock file
+#   2) Lock file is not in sync with `package.json`
+
+# In case the integrity check passes, we just use the cached/locked node modules. If it fails, we want to purge the
+# node modules and run Yarn with `--frozen-lockfile`. Running with a frozen lockfile ensures that outdated/cached node
+# modules will be refreshed to **match** the actual lock file. Otherwise, if the `package.json` does not match with
+# the lock file, Yarn automatically throws an error due to the `--frozen-lockfile` option.
+if ! (yarn check --integrity &> /dev/null); then
+  echo "Cached node modules are not in sync. Purging and refreshing..."
+  rm -rf ./node_modules/
+  yarn install --frozen-lockfile --non-interactive
+else
+  echo "Cached node modules have been checked and are in sync with the lock file."
+fi