Travis: test on nightly

Up to now, the DealerDirect plugin was a blocker for testing the standard against PHP `nightly`/ PHP 8 as it would refuse to install.

With the new version having been tagged, this issue has been removed, so we can now run the unit tests against PHP 8 to get early warning about cross-version compatibility issues which need fixing.

The builds against `nightly` remain in `allow_failures` for now.

Refs:
* https://github.com/Dealerdirect/phpcodesniffer-composer-installer/releases/tag/v0.7.0

.travis.yml

@@ -19,6 +19,7 @@ php:
   - 7.0
   - 7.1
   - 7.2
+  - "nightly"
 
 env:
   - PHPCS_VERSION="dev-master" LINT=1
@@ -133,9 +134,6 @@ jobs:
     - php: 7.4
       env: PHPCS_VERSION="4.0.x-dev@dev"
 
-    - php: "nightly"
-      env: PHPCS_VERSION="n/a" LINT=1
-
     #### CODE COVERAGE STAGE ####
     # N.B.: Coverage is only checked on the lowest and highest stable PHP versions for all PHPCS versions.
     # These builds are left out off the "test" stage so as not to duplicate test runs.
@@ -169,7 +167,7 @@ before_install:
   # On stable PHPCS versions, allow for PHP deprecation notices.
   # Unit tests don't need to fail on those for stable releases where those issues won't get fixed anymore.
   - |
-    if [[ "${TRAVIS_BUILD_STAGE_NAME^}" != "Sniff" && $PHPCS_VERSION != "dev-master" && "$PHPCS_VERSION" != "n/a" ]]; then
+    if [[ "${TRAVIS_BUILD_STAGE_NAME^}" != "Sniff" && $PHPCS_VERSION != "dev-master" ]]; then
       echo 'error_reporting = E_ALL & ~E_DEPRECATED' >> ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/travis.ini
     fi
 
@@ -178,16 +176,13 @@ before_install:
 
 install:
   # Set up test environment using Composer.
-  - |
-    if [[ $PHPCS_VERSION != "n/a" ]]; then
-      composer require --no-update --no-scripts squizlabs/php_codesniffer:${PHPCS_VERSION}
-    fi
+  - composer require --no-update --no-scripts squizlabs/php_codesniffer:${PHPCS_VERSION}
   - |
     if [[ "${TRAVIS_BUILD_STAGE_NAME^}" == "Coverage" ]]; then
       composer require --dev --no-update --no-suggest --no-scripts php-coveralls/php-coveralls:${COVERALLS_VERSION}
     fi
   - |
-    if [[ $PHPCS_VERSION == "n/a" ]]; then
+    if [[ "${TRAVIS_BUILD_STAGE_NAME^}" == "Sniff" ]]; then
       # Don't install PHPUnit when it's not needed.
       composer remove --dev phpunit/phpunit --no-update --no-scripts
     fi
@@ -208,9 +203,9 @@ script:
 
   # Run the unit tests.
   - |
-    if [[ $PHPCS_VERSION != "n/a" && "${TRAVIS_BUILD_STAGE_NAME^}" != "Coverage" ]]; then
+    if [[ "${TRAVIS_BUILD_STAGE_NAME^}" != "Coverage" ]]; then
       composer test
-    elif [[ $PHPCS_VERSION != "n/a" && "${TRAVIS_BUILD_STAGE_NAME^}" == "Coverage" ]]; then
+    elif [[ "${TRAVIS_BUILD_STAGE_NAME^}" == "Coverage" ]]; then
       composer coverage
     fi