bug#70588: hash mismatch error and stop fallback

[Simon Tournier]

Hi,

Considering something from the past – well to my knowledge it is still
an issue with the current implementation and such it will be a issue for
the future. ;-)

For instance, the R package MASS from 2019 (Guix revision 711cec):
because the CRAN project did some in-place replacements, we have a hash
mismatch and all the process stops.

--8<---------------cut here---------------start------------->8---
$ guix build 
/gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv
substitute: updating substitutes from 'https://ci.guix.gnu.org'... 100.0%
substitute: updating substitutes from 'https://bordeaux.guix.gnu.org'... 100.0%
The following derivation will be built:
  /gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv
building /gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv...

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.r-project.org/src/contrib/MASS_7.3-51.4.tar.gz...
download failed "http://cran.r-project.org/src/contrib/MASS_7.3-51.4.tar.gz"; 
404 "Not Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.rstudio.com/src/contrib/MASS_7.3-51.4.tar.gz...
download failed "http://cran.rstudio.com/src/contrib/MASS_7.3-51.4.tar.gz"; 404 
"Not Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.univ-lyon1.fr/src/contrib/MASS_7.3-51.4.tar.gz...
following redirection to 
`https://pbil.univ-lyon1.fr/CRAN/src/contrib/MASS_7.3-51.4.tar.gz'...
download failed 
"https://pbil.univ-lyon1.fr/CRAN/src/contrib/MASS_7.3-51.4.tar.gz"; 404 "Not 
Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.ism.ac.jp/src/contrib/MASS_7.3-51.4.tar.gz...
download failed "http://cran.ism.ac.jp/src/contrib/MASS_7.3-51.4.tar.gz"; 404 
"Not Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.stat.auckland.ac.nz/src/contrib/MASS_7.3-51.4.tar.gz...
download failed 
"http://cran.stat.auckland.ac.nz/src/contrib/MASS_7.3-51.4.tar.gz"; 404 "Not 
Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.mirror.ac.za/src/contrib/MASS_7.3-51.4.tar.gz...
download failed "http://cran.mirror.ac.za/src/contrib/MASS_7.3-51.4.tar.gz"; 404 
"Not Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.csie.ntu.edu.tw/src/contrib/MASS_7.3-51.4.tar.gz...
download failed "http://cran.csie.ntu.edu.tw/src/contrib/MASS_7.3-51.4.tar.gz"; 
404 "Not Found"

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From http://cran.r-project.org/src/contrib/Archive/MASS/MASS_7.3-51.4.tar.gz...
downloading from 
http://cran.r-project.org/src/contrib/Archive/MASS/MASS_7.3-51.4.tar.gz ...
 MASS_7.3-51.4.tar.gz  476KiB         2.1MiB/s 00:00 ▕██████████████████▏ 100.0%
sha256 hash mismatch for 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz:
  expected hash: 0x1ckf51y851g0kvbhsgdxb26vfpmbw3xdbcnh3ck7fjm13da4cr
  actual hash:   1swfd4jnqhsb2imznib629bywrxah7b63yqxhwhd9bhyaji70hl4
hash mismatch for store item 
'/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz'
build of /gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv 
failed
View build log at 
'/var/log/guix/drvs/wf/q2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv.gz'.
guix build: error: build of 
`/gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv' failed
--8<---------------cut here---------------end--------------->8---


When the source is correctly available in SWH:

--8<---------------cut here---------------start------------->8---
$ guix build 
/gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv
The following derivation will be built:
  /gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv
building /gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv...

[...]

Starting download of 
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
>From 
>https://archive.softwareheritage.org/api/1/content/sha256:9911d546a8d29dc906b46cb53ef8aad76d23566f4fc3b52778a1201f8a9b2c74/raw/...
downloading from 
https://archive.softwareheritage.org/api/1/content/sha256:9911d546a8d29dc906b46cb53ef8aad76d23566f4fc3b52778a1201f8a9b2c74/raw/
 ...
 raw/  476KiB                         9.9MiB/s 00:00 ▕██████████████████▏ 100.0%
successfully built 
/gnu/store/wfq2ji5x9awgyk680i1vv95hq75nx3vv-MASS_7.3-51.4.tar.gz.drv
/gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz

$ guix hash /gnu/store/gxbam95zqjaxdd6303j97z4djr907yzn-MASS_7.3-51.4.tar.gz
0x1ckf51y851g0kvbhsgdxb26vfpmbw3xdbcnh3ck7fjm13da4cr
--8<---------------cut here---------------end--------------->8---

Therefore, the bug is to not consider a hash mismatch as a fullstop and
error out but consider it as a failure of one strategy and thus try the
next strategy.

Other said, hash mismatch should be raised and obviously the content
must be discarded; then the hash mismatch should be considered as “not
found” so let try the next strategy for downloading the content.

Cheers,
simon