cabal-clean: Remove outdated cabal build artefacts from `dist-newstyle`.

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Simple command line tool to remove cabal build artefacts from `dist-newstyle/build` that are superseded by newer versions of the built package or the Haskell compiler.

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Properties

Versions	0.1.20210815, 0.1.20210924, 0.1.20220814, 0.2.20220819, 0.2.20220819, 0.2.20230609
Change log	CHANGELOG.md
Dependencies	base (>=4.9 && <5), containers (>=0.5.8), directory, filemanip (>=0.3.6.3), filepath, mtl, optparse-applicative, pretty-terminal, process, silently (>=1.2.5.2), split, string-qq [details]
License	BSD-3-Clause
Copyright	Andreas Abel, 2021, 2022
Author	Andreas Abel
Maintainer	Andreas Abel <andreas.abel@cse.gu.se>
Category	Development
Home page	https://github.com/andreasabel/cabal-clean
Bug tracker	https://github.com/andreasabel/cabal-clean/issues
Source repo	head: git clone git://github.com/andreasabel/cabal-clean.git
Uploaded	by AndreasAbel at 2022-08-19T20:00:11Z

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cabal-clean-0.2.20220819.tar.gz [browse] (Cabal source package)
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Readme for cabal-clean-0.2.20220819

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cabal-clean : Remove superseded artefacts of `cabal v2-build`

Removes compilation artefacts in dist-newstyle/build from older versions of the package or superseded minor versions of GHC.

For the impatient

Installation

cabal install cabal-clean

Run

cd $MY_PROJECT
cabal-clean

This lists the build artifacts under dist-newstyle/build.

---	191M	dist-newstyle/build/x86_64-osx/ghc-7.10.3/$MY_PROJECT-2.9.2
---	 72M	dist-newstyle/build/x86_64-osx/ghc-8.10.4/$MY_PROJECT-2.9.2
---	162M	dist-newstyle/build/x86_64-osx/ghc-9.0.1/$MY_PROJECT-2.9.2
+++	135M	dist-newstyle/build/x86_64-osx/ghc-7.10.3/$MY_PROJECT-2.9.3
---	 70M	dist-newstyle/build/x86_64-osx/ghc-8.10.4/$MY_PROJECT-2.9.3
+++	145M	dist-newstyle/build/x86_64-osx/ghc-8.10.7/$MY_PROJECT-2.9.3
---	159M	dist-newstyle/build/x86_64-osx/ghc-9.0.1/$MY_PROJECT-2.9.3

The superseded ones (assuming ghc-9.0.1 is not on the PATH), printed in red and prefixed by dashes (---), can then be removed by:

cabal-clean --delete

Rationale

v2-cabal (the nix-based cabal) maintains a directory structure for local builds of the form dist-newstyle/build/$ARCH/$HC/$PACKAGE-$VERSION (plus other stuff that does not take up much disk space). During active development with several $HC versions and $VERSION bumps for the $PACKAGE, lots of out-dated build artefacts accumulate over time.

A simple way to clean up is removing the whole dist-newstyle folder, but one might want to keep the build artefacts of the most recent package $VERSIONs of the most recent versions of the Haskell compiler ($HC).

Philosophy

Go for saving the most disk space with the simplest approach, rather than a complete clean-up. E.g., don't care about outdated contents in dist-newstyle/package-db as they take little space.
Keep only the most recent $VERSION of the package.
Keep only the most recent major versions of $HC.
Keep only versions build with a $HC which is still on the PATH (since version 0.2).
Assume a monopoly of GHC, ignoring other Haskell compilers, so only treat $HCs of the form ghc-$GHCVER.
Work autonomously, ignoring cabal files. This saves us parsing various home-grown cabal file formats. The latter could be easy using the Cabal package, but this package is not very stable, and we shy the maintenance effort of depending on Cabal.
Dry-run is the default, giving the user opportunity to review the clean-up plan.

Functionality

Read the contents of dist-newstyle/build, organizing them into a tree according to the pattern $ARCH/ghc-$GHCVER/$PACKAGE-$VERSION.
Display the outdated versions.

Try to get the disk usage with du -h and display it. (I could not find a Haskell library that gets the disk usage OS-agnostically.)
With option --delete actually remove the respective folders.

Examples

List build artifacts of current project, marking superseded ones that can be deleted:

cabal-clean

Actually delete superseded builds:

cabal-clean --delete

Delete superseded builds without changing to directory:

cabal-clean --delete path/to/my/project/dist-newstyle

Delete superseded builds in many projects:

find . -name "dist-newstyle" -exec cabal-clean --delete {} \;

Get help:

cabal-clean --help

cabal v2-clean (as of 2021-08-16)

Removes all build artefacts.
Does not have a --dry-run preview.