Description of new features in composer 2.0

Below, composer uses the tutorial column to introduce the new features of composer 2.0. I hope it will be helpful to friends in need!

#1. What are the new features?

• For command line (CLI) users

• New platform check feature checks runtime PHP version and available extensions to ensure They match project dependencies. If a mismatch is found, it will exit with error details. It is recommended to use the production PHP process during build or deployment to run composer check-platform-reqs

• If the package exists in a higher priority repository, it is now in a lower priority The package will be completely ignored in the repository. For more information, see Repository Priority.

• Invalid PSR-0/PSR-4 class configurations are no longer autoloaded in optimized autoloader mode, per the warning introduced in 1.10

• On linux systems that support the XDG base directory specification, Composer now prefers to use XDG_CONFIG_DIR/composer instead of ~/.composer (if both are available 1.x uses ~/.composer first)

• Package names must now comply with our naming guidelines, otherwise Composer will error and terminate. (https://github.com/composer/composer/blob/2.0.0/doc/04-schema.md#name)

• --no-suggest is deprecated, Since it is no longer needed

• PEAR support (repositories, downloaders, etc.) has been removed

• update now lists the composer first. lock file (update step) and then lists the changes that were applied when installing the lock file into the vendor directory (installation step)

• HTTPS_PROXY_REQUEST_FULLURI will now default to false if not specified, As this seems to work better in most environments

• dev-trunk, dev-master and dev-default are no longer aliases for each other. Keep the exact branch name for now.

2. Detailed differences in event flow during dependency resolution, composer update and installation

composer v1

• composer resolves dependencies (Scheduling PRE/POST_DEPENDENCIES_SOLVING)

• Then, it goes through all packages step by step (Scheduling PRE_PACKAGE_INSTALL/UPDATE/UNINSTALL , then schedule PRE_FILE_DOWNLOAD as needed, then POST_PACKAGE_*).

• Finally write the lock file at the end

composer v2

• The update and installation processes have been split.

Update meeting:

• composer resolves dependencies (scheduling PRE_POOL_CREATE)

• Then write the lock file, update is completed

Then install:

• Send to PRE_OPERATIONS_EXEC to execute Full list of operations

• Download all packages not already in cache in parallel (scheduling PRE_FILE_DOWNLOAD for packages not yet in cache)

• Then , which iterates through all packages and performs updates/installs/uninstalls in parallel (PRE_PACKAGE_INSTALL/UPDATE/UNINSTALL is distributed first, then POST_PACKAGE_*, but the last package launched may finish installing before another one is completed).

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