Learn common build configurations
In the build process section, we mentioned the elaborated install plan which is a detailed plan on how exactly to build all the packages in your build. There are cases in which we want to modify the configuration for certain packages in our build.
While the .cabal specifies how to build a single package, a cabal.project specifies how to build all the packages in your project. In most simple use cases, you never have to worry about this file since it has smart defaults. The default is to automatically pick up packages - subfolders in your project with .cabal files.
When you're building a release version of your app, you may want to build with optimizations turned on for all your dependencies.
packages: . all-packages optimization: 2
The all-packages section apply configuration to all packages in your build, both local and external.
To ensure full reproducibility of the build for your app, it is a good idea to freeze the dependencies so that your project build occurs in exactly the same way every time, independent of Hackage/Etlas Index changes.
$ etlas freeze
This will create a file called cabal.project.freeze in the current folder that contains a list of hard constraints for all the packages in your build. A freeze file ensures that the outcome dependency resolution is stable.
In practice, you should not freeze dependencies for libraries.