Travis CI: Why does composer sometimes install whole packages, and sometimes not? - composer-php

Question

Sometimes when Travis CI is building my package, there's a short list of dependencies, like so:
$ composer install --prefer-source --no-interaction --dev
You are using the deprecated option "--dev". It has no effect and will break in Composer 3.
Installing dependencies from lock file (including require-dev)
Verifying lock file contents can be installed on current platform.
Nothing to install, update or remove
Generating optimized autoload files
> Illuminate\Foundation\ComposerScripts::postAutoloadDump
> #php artisan package:discover --ansi
Discovered Package: facade/ignition
Discovered Package: fideloper/proxy
Discovered Package: fruitcake/laravel-cors
Discovered Package: intervention/image
Discovered Package: kitloong/laravel-migrations-generator
Discovered Package: laravel/breeze
Discovered Package: laravel/cashier
Discovered Package: laravel/sail
Discovered Package: laravel/tinker
Discovered Package: nesbot/carbon
Discovered Package: nunomaduro/collision
Discovered Package: simplesoftwareio/simple-qrcode
Discovered Package: vemcogroup/laravel-sparkpost-driver
Package manifest generated successfully.
And sometimes there's a huge list, like this:
$ composer install --prefer-source --no-interaction --dev
You are using the deprecated option "--dev". It has no effect and will break in Composer 3.
Installing dependencies from lock file (including require-dev)
Verifying lock file contents can be installed on current platform.
Package operations: 0 installs, 48 updates, 0 removals
- Syncing symfony/polyfill-ctype (v1.22.1) into cache
- Syncing webmozart/assert (1.10.0) into cache
- Syncing symfony/polyfill-php72 (v1.22.1) into cache
- Syncing symfony/polyfill-intl-normalizer (v1.22.1) into cache
- Syncing symfony/polyfill-intl-idn (v1.22.1) into cache
- Syncing symfony/polyfill-php80 (v1.22.1) into cache
- Syncing symfony/polyfill-mbstring (v1.22.1) into cache
- Syncing symfony/var-dumper (v5.2.5) into cache
- Syncing symfony/polyfill-intl-grapheme (v1.22.1) into cache
- Syncing symfony/string (v5.2.4) into cache
- Syncing psr/container (1.1.1) into cache
- Syncing symfony/polyfill-php73 (v1.22.1) into cache
- Syncing symfony/console (v5.2.5) into cache
- Syncing vlucas/phpdotenv (v5.3.0) into cache
- Syncing symfony/css-selector (v5.2.4) into cache
- Syncing symfony/routing (v5.2.4) into cache
- Syncing symfony/process (v5.2.4) into cache
- Syncing symfony/mime (v5.2.5) into cache
- Syncing symfony/http-foundation (v5.2.4) into cache
- Syncing symfony/event-dispatcher (v5.2.4) into cache
- Syncing symfony/error-handler (v5.2.4) into cache
- Syncing symfony/http-kernel (v5.2.5) into cache
- Syncing symfony/finder (v5.2.4) into cache
- Syncing symfony/polyfill-iconv (v1.22.1) into cache
- Syncing swiftmailer/swiftmailer (v6.2.7) into cache
- Syncing ramsey/collection (1.1.3) into cache
- Syncing brick/math (0.9.2) into cache
- Syncing symfony/translation (v5.2.5) into cache
- Syncing nesbot/carbon (2.46.0) into cache
- Syncing league/mime-type-detection (1.7.0) into cache
- Syncing laravel/framework (v8.33.0) into cache
- Syncing filp/whoops (2.10.0) into cache
- Syncing facade/flare-client-php (1.4.0) into cache
- Syncing facade/ignition (2.5.14) into cache
- Syncing asm89/stack-cors (v2.0.3) into cache
- Syncing guzzlehttp/promises (1.4.1) into cache
- Syncing laravel/breeze (v1.1.3) into cache
- Syncing symfony/polyfill-intl-icu (v1.22.1) into cache
- Syncing symfony/intl (v5.2.4) into cache
- Syncing stripe/stripe-php (v7.75.0) into cache
- Syncing laravel/cashier (v12.10.0) into cache
- Syncing laravel/sail (v1.4.8) into cache
- Syncing psy/psysh (v0.10.7) into cache
- Syncing laravel/tinker (v2.6.1) into cache
- Syncing mockery/mockery (1.4.3) into cache
- Syncing nunomaduro/collision (v5.3.0) into cache
- Syncing phar-io/version (3.1.0) into cache
- Syncing phpunit/phpunit (9.5.2) into cache
- Upgrading symfony/polyfill-ctype (v1.22.0 => v1.22.1): Checking out c6c942b1ac from cache
- Upgrading webmozart/assert (1.9.1 => 1.10.0): Checking out 6964c76c78 from cache
- Upgrading symfony/polyfill-php72 (v1.22.0 => v1.22.1): Checking out cc6e6f9b39 from cache
- Upgrading symfony/polyfill-intl-normalizer (v1.22.0 => v1.22.1): Checking out 43a0283138 from cache
- Upgrading symfony/polyfill-intl-idn (v1.22.0 => v1.22.1): Checking out 2d63434d92 from cache
- Upgrading symfony/polyfill-php80 (v1.22.0 => v1.22.1): Checking out dc3063ba22 from cache
- Upgrading symfony/polyfill-mbstring (v1.22.0 => v1.22.1): Checking out 5232de97ee from cache
- Upgrading symfony/var-dumper (v5.2.1 => v5.2.5): Checking out 002ab5a367 from cache
- Upgrading symfony/polyfill-intl-grapheme (v1.22.0 => v1.22.1): Checking out 5601e09b69 from cache
- Upgrading symfony/string (v5.2.1 => v5.2.4): Checking out 4e78d7d470 from cache
- Upgrading psr/container (1.0.0 => 1.1.1): Checking out 8622567409 from cache
- Upgrading symfony/polyfill-php73 (v1.22.0 => v1.22.1): Checking out a678b42e92 from cache
- Upgrading symfony/console (v5.2.1 => v5.2.5): Checking out 938ebbadae from cache
- Upgrading vlucas/phpdotenv (v5.2.0 => v5.3.0): Checking out b3eac5c7ac from cache
- Upgrading symfony/css-selector (v5.2.1 => v5.2.4): Checking out f65f217b33 from cache
- Upgrading symfony/routing (v5.2.1 => v5.2.4): Checking out cafa138128 from cache
- Upgrading symfony/process (v5.2.1 => v5.2.4): Checking out 313a38f09c from cache
- Upgrading symfony/mime (v5.2.1 => v5.2.5): Checking out 554ba128f1 from cache
- Upgrading symfony/http-foundation (v5.2.1 => v5.2.4): Checking out 54499baea7 from cache
- Upgrading symfony/event-dispatcher (v5.2.1 => v5.2.4): Checking out d08d6ec121 from cache
- Upgrading symfony/error-handler (v5.2.1 => v5.2.4): Checking out b547d3babc from cache
- Upgrading symfony/http-kernel (v5.2.1 => v5.2.5): Checking out b8c63ef63c from cache
- Upgrading symfony/finder (v5.2.1 => v5.2.4): Checking out 0d639a0943 from cache
- Upgrading symfony/polyfill-iconv (v1.22.0 => v1.22.1): Checking out 06fb361659 from cache
- Upgrading swiftmailer/swiftmailer (v6.2.5 => v6.2.7): Checking out 15f7faf850 from cache
- Upgrading ramsey/collection (1.1.1 => 1.1.3): Checking out 28a5c4ab2f from cache
- Upgrading brick/math (0.9.1 => 0.9.2): Checking out dff976c2f3 from cache
- Upgrading symfony/translation (v5.2.1 => v5.2.5): Checking out 0947ab1e3a from cache
RuntimeException]
Source directory /home/travis/build/SecretGroup/MEMBERSHIP-0.2/vendor/nesbot/carbon has uncommitted changes.
Both times used the same .travis.yml file. So why did one think there was nothing to install, while the other tried to install a lot of packages (and then failed)?

Answer 1

Travis CI keeps a cache of your vendor folder in order to make builds run quicker (and reduce unnecessary traffic for them). If you've made some changes to your composer.lock file Travis CI may need to update the files stored in the vendor folder.
Other times it won't need to do this, and so will have a shorter build time.