refactor(tvix/nix-compat): rename NixHashWithMode -> CAHash r/6871

This specific struct is only used to represent content-addressed paths
(in case a Derivation has a fixed-output hash, for example).
Rename `Output`'s `hash_with_mode` to `ca_hash`.

We now also include `CAHash::Text`, and update the `validate` function
of the `Output` struct to reject text hashes there.

This allows cleaning up the various output path calculation functions
inside nix-compat/src/store_path/utils.rs, as they can now match on
the type.

`make_type` is renamed to `make_references_string`,
`build_regular_ca_path` is renamed to `build_ca_path`, and
`build_text_path` has a disclaimer added, because you might not actually
want to use it.

Change-Id: I674d065f2ed5c804012ddfed56e161ac49d23931
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9814
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>

1 files changed, 5 insertions, 9 deletions

diff --git a/tvix/nix-compat/src/derivation/write.rs b/tvix/nix-compat/src/derivation/write.rs
index 7ebbbffa4b55..087227c99998 100644
--- a/tvix/nix-compat/src/derivation/write.rs
+++ b/tvix/nix-compat/src/derivation/write.rs
@@ -4,7 +4,7 @@
 //! [ATerm]: http://program-transformation.org/Tools/ATermFormat.html
 
 use crate::aterm::escape_bytes;
-use crate::derivation::output::Output;
+use crate::derivation::{ca_kind_prefix, output::Output};
 use bstr::BString;
 use std::{
     collections::{BTreeMap, BTreeSet},
@@ -79,14 +79,10 @@ pub fn write_outputs(
 
         let mut elements: Vec<&str> = vec![output_name, &output.path];
 
-        let (mode_and_algo, digest) = match &output.hash_with_mode {
-            Some(crate::nixhash::NixHashWithMode::Flat(h)) => (
-                h.algo().to_string(),
-                data_encoding::HEXLOWER.encode(h.digest_as_bytes()),
-            ),
-            Some(crate::nixhash::NixHashWithMode::Recursive(h)) => (
-                format!("r:{}", h.algo()),
-                data_encoding::HEXLOWER.encode(h.digest_as_bytes()),
+        let (mode_and_algo, digest) = match &output.ca_hash {
+            Some(ca_hash) => (
+                format!("{}{}", ca_kind_prefix(ca_hash), ca_hash.digest().algo()),
+                data_encoding::HEXLOWER.encode(ca_hash.digest().digest_as_bytes()),
             ),
             None => ("".to_string(), "".to_string()),
         };