The lock file is not up to date with the latest changes in composer.json

Question

I'm trying to clone a github repository and issue a composer install on it. But I am getting this:

Warning: The lock file is not up to date with the latest changes in composer.json. You may be getting outdated dependencies. Run update to update them.

Your requirements could not be resolved to an installable set of packages.  
  Problem 1  
    - Conclusion: remove symfony/polyfill-intl-icu v1.9.0  
    - Installation request for symfony/polyfill-intl-icu v1.9.0 -> satisfiable by symfony/polyfill-intl-icu[v1.9.0].  
    - Conclusion: remove symfony/process v3.4.15  
    - symfony/polyfill-intl-icu v1.9.0 requires symfony/intl ~2.3|~3.0|~4.0 -> satisfiable by symfony/symfony[v4.0.0].  
    - don't install symfony/process v3.4.15|remove symfony/symfony v4.0.0  
    - don't install symfony/symfony v4.0.0|don't install symfony/process v3.4.15  
    - Installation request for symfony/process v3.4.15 -> satisfiable by symfony/process[v3.4.15].  

When running composer update

Problem 1
- Conclusion: don't install symfony/symfony v4.1.7
- Conclusion: don't install symfony/symfony v4.1.6
- Conclusion: don't install symfony/symfony v4.1.5
- Conclusion: don't install symfony/symfony v4.1.4
- Conclusion: don't install symfony/symfony v4.1.3
- Conclusion: don't install symfony/symfony v4.1.2
- Conclusion: don't install symfony/symfony v4.1.1
- Conclusion: don't install symfony/symfony v4.1.0
- Conclusion: don't install symfony/symfony v4.0.14
- Conclusion: don't install symfony/symfony v4.0.13
- Conclusion: don't install symfony/symfony v4.0.12
- Conclusion: don't install symfony/symfony v4.0.11
- Conclusion: don't install symfony/symfony v4.0.10
- Conclusion: don't install symfony/symfony v4.0.9
- Conclusion: don't install symfony/symfony v4.0.8
- Conclusion: don't install symfony/symfony v4.0.7
- Conclusion: don't install symfony/symfony v4.0.6
- Conclusion: don't install symfony/symfony v4.0.5
- Conclusion: don't install symfony/symfony v4.0.4
- Conclusion: don't install symfony/symfony v4.0.3
- Conclusion: don't install symfony/symfony v4.0.2
- Conclusion: don't install symfony/symfony v4.0.1
- Conclusion: remove symfony/symfony v4.0.0
- don't install symfony/symfony v4.0.0|remove symfony/process v3.4.15
- don't install symfony/process v3.3.0|don't install symfony/symfony v4.0.0

composer.json (require section)

"require": {
    "php": ">=7.1",
    "symfony/symfony": "~4.0",
    "symfony/process": "^3.3",
    "doctrine/orm": "dev-fork as 2.5.6",
    "doctrine/doctrine-bundle": "1.*",
    "symfony/swiftmailer-bundle": "~3.1",
    "symfony/monolog-bundle": "~3.1",
    "sensio/framework-extra-bundle": "^5.1",
    "graylog2/gelf-php": "^1.4",
    "doctrine/doctrine-migrations-bundle": "^1.1",
    "awt/webauth-bundle": "3.0.*",
    "awt/canvas-client-bundle": "6.2.*"
}

Answer 1

You may use depends & prohibits on composer to see what exactly you should do:

composer depends symfony/process 3.4.15

and

composer prohibits symfony/symfony 4

This two commands tell you what is the conflict and what you should do.

The main problem is that your composer.json and composer.lock are not in sync. The first file tells composer what are required package & their version constraints, and the second one shares the exact same package version between collaborators, for consistency.

If the repository owner does not help you with this problem, the only way you have is:

rm composer.lock
rm -rf vendor
composer install

This will remove vendor directory contents and install a fressh copy of all dependencies, according to just composer.json