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Diffstat (limited to 'tvix/docs/src/differences-drv-paths.md')
| -rw-r--r-- | tvix/docs/src/differences-drv-paths.md | 35 |
1 files changed, 0 insertions, 35 deletions
diff --git a/tvix/docs/src/differences-drv-paths.md b/tvix/docs/src/differences-drv-paths.md deleted file mode 100644 index f1c90bd528..0000000000 --- a/tvix/docs/src/differences-drv-paths.md +++ /dev/null @@ -1,35 +0,0 @@ -# .drvPath inconsistencies / Why .drvPath differs between Nix and Tvix - -Nix and Tvix currently use a different approach when it comes to tracking input -references, in order to build the right dependencies in advance. -Nix is using string contexts, whereas Tvix is doing reference scanning [^inbox-drvpath]. - -There are some real-life cases, for example during nixpkgs bootstrapping, where -multiple different fixed-output derivations are written to produce the same -hash. - -For example, bootstrap sources that are downloaded early are fetched using -a special "builder hack", in which the `builder` field of the derivation is -populated with the magic string `builtin:fetchurl` and the builder itself will -perform a fetch, with everything looking like a normal derivation to the user. - -These bootstrap sources are later on defined *again*, once `curl`is available, -to be downloaded using the standard pkgs.fetchtarball mechanism, but yielding -the *same* outputs (as the same files are being fetched). - -In our reference scanning implementation, this output scanning of FOD will -cause the path of the *first* derivation producing the given fixed output to be -stored in the `inputDrvs` field of the derivation, while Nix will point to the -derivation that was actually used. - -This doesn't cause any differences in the calculated *output paths*, as paths to -fixed-output derivations are replaced with a special -`fixed:out:${algo}:${digest}:${fodPath}` string that doesn't contain the "path -to the wrong derivation" anymore. - -As we haven't fully determined if our reference scanning approach is gonna work, -and comparing output paths is sufficient to determine equality of the build -instructions, this is left as a future work item. - - -[^inbox-drvpath]: https://inbox.tvl.su/depot/20230316120039.j4fkp3puzrtbjcpi@tp/T/#t |