Move WHEEL file parsing into a struct (#15483)

## Summary

No functional changes, but I need to add more behavior here for
https://github.com/astral-sh/uv/issues/15035, so seems nice to do this
separately.

crates/uv-install-wheel/src/install.rs

@@ -14,7 +14,7 @@ use uv_pypi_types::{DirectUrl, Metadata10};
 
 use crate::linker::{LinkMode, Locks};
 use crate::wheel::{
-    LibKind, dist_info_metadata, find_dist_info, install_data, parse_scripts, parse_wheel_file,
+    LibKind, WheelFile, dist_info_metadata, find_dist_info, install_data, parse_scripts,
     read_record_file, write_installer_metadata, write_script_entrypoints,
 };
 use crate::{Error, Layout};
@@ -66,7 +66,7 @@ pub fn install_wheel<Cache: serde::Serialize, Build: serde::Serialize>(
         .as_ref()
         .join(format!("{dist_info_prefix}.dist-info/WHEEL"));
     let wheel_text = fs::read_to_string(wheel_file_path)?;
-    let lib_kind = parse_wheel_file(&wheel_text)?;
+    let lib_kind = WheelFile::parse(&wheel_text)?.lib_kind();
 
     // > 1.c If Root-Is-Purelib == ‘true’, unpack archive into purelib (site-packages).
     // > 1.d Else unpack archive into platlib (site-packages).

crates/uv-install-wheel/src/lib.rs

@@ -13,7 +13,7 @@ use uv_pypi_types::Scheme;
 pub use install::install_wheel;
 pub use linker::{LinkMode, Locks};
 pub use uninstall::{Uninstall, uninstall_egg, uninstall_legacy_editable, uninstall_wheel};
-pub use wheel::{LibKind, parse_wheel_file, read_record_file};
+pub use wheel::{LibKind, WheelFile, read_record_file};
 
 mod install;
 mod linker;

crates/uv-install-wheel/src/wheel.rs

@@ -257,35 +257,19 @@ pub(crate) fn write_script_entrypoints(
     Ok(())
 }
 
-/// Whether the wheel should be installed into the `purelib` or `platlib` directory.
+/// A parsed `WHEEL` file.
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
-pub enum LibKind {
+pub struct WheelFile(FxHashMap<String, Vec<String>>);
-    /// Install into the `purelib` directory.
-    Pure,
-    /// Install into the `platlib` directory.
-    Plat,
-}
 
-/// Parse WHEEL file.
+impl WheelFile {
+    /// Parse `WHEEL` file.
     ///
     /// > {distribution}-{version}.dist-info/WHEEL is metadata about the archive itself in the same
     /// > email message format:
-pub fn parse_wheel_file(wheel_text: &str) -> Result<LibKind, Error> {
+    pub fn parse(wheel_text: &str) -> Result<Self, Error> {
         // {distribution}-{version}.dist-info/WHEEL is metadata about the archive itself in the same email message format:
         let data = parse_email_message_file(&mut wheel_text.as_bytes(), "WHEEL")?;
 
-    // Determine whether Root-Is-Purelib == ‘true’.
-    // If it is, the wheel is pure, and should be installed into purelib.
-    let root_is_purelib = data
-        .get("Root-Is-Purelib")
-        .and_then(|root_is_purelib| root_is_purelib.first())
-        .is_some_and(|root_is_purelib| root_is_purelib == "true");
-    let lib_kind = if root_is_purelib {
-        LibKind::Pure
-    } else {
-        LibKind::Plat
-    };
-
         // mkl_fft-1.3.6-58-cp310-cp310-manylinux2014_x86_64.whl has multiple Wheel-Version entries, we have to ignore that
         // like pip
         let wheel_version = data
@@ -302,7 +286,7 @@ pub fn parse_wheel_file(wheel_text: &str) -> Result<LibKind, Error> {
         // and technically we only need to check that the version is not higher
         if wheel_version == ("0", "1") {
             warn!("Ancient wheel version 0.1 (expected is 1.0)");
-        return Ok(lib_kind);
+            return Ok(Self(data));
         }
         // Check that installer is compatible with Wheel-Version. Warn if minor version is greater, abort if major version is greater.
         // Wheel-Version: 1.0
@@ -318,7 +302,38 @@ pub fn parse_wheel_file(wheel_text: &str) -> Result<LibKind, Error> {
                 0, wheel_version.1
             );
         }
-    Ok(lib_kind)
+        Ok(Self(data))
+    }
+
+    /// Whether the wheel should be installed into the `purelib` or `platlib` directory.
+    pub fn lib_kind(&self) -> LibKind {
+        // Determine whether Root-Is-Purelib == ‘true’.
+        // If it is, the wheel is pure, and should be installed into purelib.
+        let root_is_purelib = self
+            .0
+            .get("Root-Is-Purelib")
+            .and_then(|root_is_purelib| root_is_purelib.first())
+            .is_some_and(|root_is_purelib| root_is_purelib == "true");
+        if root_is_purelib {
+            LibKind::Pure
+        } else {
+            LibKind::Plat
+        }
+    }
+
+    /// Return the list of wheel tags.
+    pub fn tags(&self) -> Option<&[String]> {
+        self.0.get("Tag").map(Vec::as_slice)
+    }
+}
+
+/// Whether the wheel should be installed into the `purelib` or `platlib` directory.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum LibKind {
+    /// Install into the `purelib` directory.
+    Pure,
+    /// Install into the `platlib` directory.
+    Plat,
 }
 
 /// Moves the files and folders in src to dest, updating the RECORD in the process
@@ -938,7 +953,7 @@ mod test {
     use crate::wheel::format_shebang;
 
     use super::{
-        RecordEntry, Script, get_script_executable, parse_email_message_file, parse_wheel_file,
+        RecordEntry, Script, WheelFile, get_script_executable, parse_email_message_file,
         read_record_file, write_installer_metadata,
     };
 
@@ -1013,8 +1028,8 @@ mod test {
                 version
             }
         }
-        parse_wheel_file(&wheel_with_version("1.0")).unwrap();
+        WheelFile::parse(&wheel_with_version("1.0")).unwrap();
-        parse_wheel_file(&wheel_with_version("2.0")).unwrap_err();
+        WheelFile::parse(&wheel_with_version("2.0")).unwrap_err();
     }
 
     #[test]