Align with cargo (#69)

As noted in the comment, this changes the url kind from `u64` -> `usize`
to match cargo, which unfortunately uses the default `derive(Hash)`
which for enums uses `::core::intrinsics::discriminant_value` which for
non-repr enums is...pointer size. This means the hash computed is
different between 32 and 64-bit targets when they could easily be the
same. :(

Resolves:
EmbarkStudios/cargo-deny#540 (comment)

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 <!-- next-header -->
 ## [Unreleased] - ReleaseDate
+### Fixed
+- [PR#69](https://github.com/EmbarkStudios/tame-index/pull/69) resolved an issue where 32-bit targets would have a different ident hash from what cargo would have due to cargo being target dependent in the hash calculation.
+
 ## [0.13.0] - 2024-07-25
 ### Changed
 - [PR#67](https://github.com/EmbarkStudios/tame-index/pull/67) updated `gix` -> 0.64.

src/utils.rs

@@ -104,9 +104,16 @@ pub fn canonicalize_url(url: &str) -> Result<String, Error> {
 pub fn url_to_local_dir(url: &str) -> Result<UrlDir, Error> {
     use std::hash::{Hash, Hasher, SipHasher};
 
-    const GIT_REPO: u64 = 0;
-    const GIT_REGISTRY: u64 = 2;
-    const SPARSE_REGISTRY: u64 = 3;
+    // This is extremely irritating, but we need to use usize for the kind, which
+    // impacts the hash calculation, making it different based on pointer size.
+    //
+    // The reason for this is that cargo just uses #[derive(Hash)] for the SourceKind
+    // https://github.com/rust-lang/cargo/blob/88b4b3bcd3bbb66873734d97ae412a6bcf9b75ee/crates/cargo-util-schemas/src/core/source_kind.rs#L4-L5,
+    // which then uses https://doc.rust-lang.org/core/intrinsics/fn.discriminant_value.html
+    // to get the discriminant and add to the hash...and that is pointer width :(
+    const GIT_REPO: usize = 0;
+    const GIT_REGISTRY: usize = 2;
+    const SPARSE_REGISTRY: usize = 3;
 
     // Ensure we have a registry or bare url
     let (url, scheme_ind, kind) = {
@@ -272,7 +279,7 @@ mod test {
     use crate::PathBuf;
 
     #[test]
-    #[cfg(target_endian = "little")]
+    #[cfg(all(target_pointer_width = "64", target_endian = "little"))]
     fn canonicalizes_git_urls() {
         let super::UrlDir { dir_name, canonical } = url_to_local_dir("git+https://github.com/EmbarkStudios/cpal.git?rev=d59b4de#d59b4decf72a96932a1482cc27fe4c0b50c40d32").unwrap();
 
@@ -322,7 +329,7 @@ mod test {
     }
 
     #[test]
-    #[cfg(target_endian = "little")]
+    #[cfg(all(target_pointer_width = "64", target_endian = "little"))]
     fn matches_cargo() {
         assert_eq!(
             get_index_details(crate::CRATES_IO_INDEX, Some(PathBuf::new())).unwrap(),
@@ -369,6 +376,18 @@ mod test {
         );
     }
 
+    #[test]
+    #[cfg(all(target_pointer_width = "32", target_endian = "little"))]
+    fn matches_cargo_32bit() {
+        assert_eq!(
+            get_index_details(crate::CRATES_IO_HTTP_INDEX, Some(PathBuf::new())).unwrap(),
+            (
+                "registry/index/index.crates.io-1cd66030c949c28d".into(),
+                crate::CRATES_IO_HTTP_INDEX.to_owned(),
+            )
+        );
+    }
+
     #[test]
     fn gets_cargo_version() {
         const MINIMUM: semver::Version = semver::Version::new(1, 70, 0);

tests/cache.rs

@@ -1,3 +1,11 @@
+#![cfg(target_pointer_width = "64")]
+
+//! Note we only run these tests if _built_ for 64-bit, as the only test targets
+//! this project cares about are 64 bit, and the issue is that, to match cargo
+//! we need to calculate the hash of the index the same, the rub is that when
+//! running a 32-bit target (eg. i686) on a 64-bit host where the cargo on the
+//! host is built for the 64-bit target as well, the local directories won't match
+
 mod utils;
 
 use tame_index::{index::cache::ValidCacheEntry, utils::get_index_details, IndexCache};