cabal-clean-0.2.20220819: README.md
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cabal-clean : Remove superseded artefacts of `cabal v2-build`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versions of the package or superseded minor versions of GHC.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 $MY_PROJECT
cabal-clean
This lists the build artifacts under `dist-newstyle/build`.
```diff
--- 191M dist-newstyle/build/x86_64-osx/ghc-7.10.3/$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The superseded ones (assuming `ghc-9.0.1` is not on the `PATH`),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 `$PACKAGE`,
lots of out-dated build artefacts accumulate over time.
A simple way to clean up is removing the whole `dist-newstyle` folder,
but one might want to keep the build artefacts of the most recent
package `$VERSION`s 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 E.g., don't care about outdated contents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 `$HC`s of the form `ghc-$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
Related
-------
`cabal v2-clean` (as of 2021-08-16)
- Removes *all* build artefacts.
- Does not have a `--dry-run` preview.