Snippets cannot be used when the source archive is not supported by tar. For example, when building HISAT with snippets (instead of patching in a build phase), guix determines the decompression type to be "xz" and then fails as follows:
~~~~~~~ The following derivations will be built: /gnu/store/jra0psbhjkcf66rdmj5bshivf32nyf73-hisat-0.1.4.drv /gnu/store/1hpkf8yl4hcifzalnwh2hj6qwi8jid3w-hisat-0.1.4-beta-source.tar.xz.drv /gnu/store/pri51516agpcm9k6asgbdmspxnim3l7q-hisat-0.1.4.drv @ build-started /gnu/store/1hpkf8yl4hcifzalnwh2hj6qwi8jid3w-hisat-0.1.4-beta-source.tar.xz.drv - x86_64-linux /var/log/guix/drvs/1h//pkf8yl4hcifzalnwh2hj6qwi8jid3w-hisat-0.1.4-beta-source.tar.xz.drv.bz2 /gnu/store/c4km8376y174q7gxqahf4hc1i1xaqkqh-tar-1.28/bin/tar: This does not look like a tar archive /gnu/store/c4km8376y174q7gxqahf4hc1i1xaqkqh-tar-1.28/bin/tar: Skipping to next header /gnu/store/c4km8376y174q7gxqahf4hc1i1xaqkqh-tar-1.28/bin/tar: Exiting with failure status due to previous errors builder for `/gnu/store/1hpkf8yl4hcifzalnwh2hj6qwi8jid3w-hisat-0.1.4-beta-source.tar.xz.drv' failed with exit code 1 @ build-failed /gnu/store/1hpkf8yl4hcifzalnwh2hj6qwi8jid3w-hisat-0.1.4-beta-source.tar.xz.drv - 1 builder for `/gnu/store/1hpkf8yl4hcifzalnwh2hj6qwi8jid3w-hisat-0.1.4-beta-source.tar.xz.drv' failed with exit code 1 cannot build derivation `/gnu/store/pri51516agpcm9k6asgbdmspxnim3l7q-hisat-0.1.4.drv': 1 dependencies couldn't be built cannot build derivation `/gnu/store/jra0psbhjkcf66rdmj5bshivf32nyf73-hisat-0.1.4.drv': 1 dependencies couldn't be built killing process 2524 guix build: error: build failed: build of `/gnu/store/jra0psbhjkcf66rdmj5bshivf32nyf73-hisat-0.1.4.drv' failed ~~~~~~~ That's due to the definiton of `decompression-type' in `patch-and-repack' in the file guix/packages.scm: ~~~~~~ (define decompression-type (cond ((string-suffix? "gz" source-file-name) "gzip") ((string-suffix? "bz2" source-file-name) "bzip2") ((string-suffix? "lz" source-file-name) "lzip") (else "xz"))) ~~~~~~