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author | Ryan Lahfa <tvl@lahfa.xyz> | 2023-08-19T16·36+0200 |
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committer | raitobezarius <tvl@lahfa.xyz> | 2023-08-20T19·34+0000 |
commit | d504b440c2ac420b6618b5caa5b08684575cf2ba (patch) | |
tree | d40014f01b2010f26312610dfbaba6cbe5e4fdb2 /third_party/nix/src/tests/lang/eval-okay-attrs4.nix | |
parent | bb48d8c61bed61e3c9318e214c838df74b60ee8e (diff) |
feat(tvix/nix-compat): don't swallow hash validation errors r/6494
Previously, Output deserialization would silence validation errors and provide `None` for `hash_with_mode` as soon as a validation error would happen inside of the `NixHashWithMode` deserialization, e.g. invalid hash length would not provide an validation error but a silent `None` value. This is problematic, we workaround a serde limitation here by writing our own Deserializer. As you can see, we write some boilerplate code unfortunately, as, for example: - `#[serde(fail_if_unparsed_as="Option::is_none")]` is not a thing, otherwise, we could have been able to just bubble up errors in case of "not fully parsed" (and not missing) values. - `From<&serde_json::Value> for serde::de::Unexpected` is not a thing, otherwise, we could just map invalid type errors and reuse the existing types instead of doing extremely bizarre things with `serde::de::Unexpected::Other`, note: this is a not problem for expected, we know what we expect, we don't know what we received in practice. I decided to write a `NixHashWithMode::from_map` which will eat a map deserialized via `serde_json`, so our serde magic is not totally "data model" agnostic. I wanted to go for data model agnosticity and enable maximal performance, e.g. building the structure as the map values are streamed in the Visitor, this is needlessly painful because `Output` and `NixHashWithMode` are in different files and this really makes sense only if we write the full implementation in one file, indeed, otherwise, you end up duplicating the work or having strange coupling. So, for now, we will allocate a full map of the fields inside the `Output`, i.e. if any "unknown field" is in that map, we will deserialize it for no reason. Doing it properly, as I repeat it in the code and to flokli at C3Camp 2023, requires to patch serde upstream IMHO. Change-Id: I46fe6ccb8c390c48d6934fd3e3f02a0dfe59557b Reviewed-on: https://cl.tvl.fyi/c/depot/+/9107 Tested-by: BuildkiteCI Reviewed-by: flokli <flokli@flokli.de>
Diffstat (limited to 'third_party/nix/src/tests/lang/eval-okay-attrs4.nix')
0 files changed, 0 insertions, 0 deletions