To obtain the latest development version of Psalm, a snapshot build can be downloaded from GitHub at https://github.com/vimeo/psalm/archive/refs/heads/5.x.zip
Snapshot builds typically include only the source code and exclude the .git
directory. As a result, Psalm cannot automatically determine its version or
revision when executing composer install, since this information is usually
derived from the git repository metadata that Composer relies on.
To successfully install Psalm from a snapshot build, it is necessary to
manually specify the version using the COMPOSER_ROOT_VERSION environment
variable. This allows Composer to proceed with the installation of Psalm.
The command to do so is as follows:
COMPOSER_ROOT_VERSION=5.x-dev composer install