Unify python interpreter abstractions (#178)

Previously, we had two python interpreter metadata structs, one in
gourgeist and one in puffin. Both would spawn a subprocess to query
overlapping metadata and both would appear in the cli crate, if you
weren't careful you could even have to different base interpreters at
once. This change unifies this to one set of metadata, queried and
cached once.

Another effect of this crate is proper separation of python interpreter
and venv. A base interpreter (such as `/usr/bin/python/`, but also pyenv
and conda installed python) has a set of metadata. A venv has a root and
inherits the base python metadata except for `sys.prefix`, which unlike
`sys.base_prefix`, gets set to the venv root. From the root and the
interpreter info we can compute the paths inside the venv. We can reuse
the interpreter info of the base interpreter when creating a venv
without having to query the newly created `python`.

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

@@ -75,14 +75,14 @@ impl AsRef<Path> for LockedDir {
 /// non-deterministically fail.
 pub struct InstallLocation<T> {
     /// absolute path
-    venv_base: T,
+    venv_root: T,
     python_version: (u8, u8),
 }
 
 impl<T: AsRef<Path>> InstallLocation<T> {
     pub fn new(venv_base: T, python_version: (u8, u8)) -> Self {
         Self {
-            venv_base,
+            venv_root: venv_base,
             python_version,
         }
     }
@@ -90,10 +90,10 @@ impl<T: AsRef<Path>> InstallLocation<T> {
     /// Returns the location of the `python` interpreter.
     pub fn python(&self) -> PathBuf {
         if cfg!(windows) {
-            self.venv_base.as_ref().join("Scripts").join("python.exe")
+            self.venv_root.as_ref().join("Scripts").join("python.exe")
         } else {
             // canonicalize on python would resolve the symlink
-            self.venv_base.as_ref().join("bin").join("python")
+            self.venv_root.as_ref().join("bin").join("python")
         }
     }
 
@@ -101,25 +101,25 @@ impl<T: AsRef<Path>> InstallLocation<T> {
         self.python_version
     }
 
-    pub fn venv_base(&self) -> &T {
-        &self.venv_base
+    pub fn venv_root(&self) -> &T {
+        &self.venv_root
     }
 }
 
 impl InstallLocation<PathBuf> {
     pub fn acquire_lock(&self) -> io::Result<InstallLocation<LockedDir>> {
-        let locked_dir = if let Some(locked_dir) = LockedDir::try_acquire(&self.venv_base)? {
+        let locked_dir = if let Some(locked_dir) = LockedDir::try_acquire(&self.venv_root)? {
             locked_dir
         } else {
             warn!(
                 "Could not acquire exclusive lock for installing, is another installation process \
                 running? Sleeping until lock becomes free"
             );
-            LockedDir::acquire(&self.venv_base)?
+            LockedDir::acquire(&self.venv_root)?
         };
 
         Ok(InstallLocation {
-            venv_base: locked_dir,
+            venv_root: locked_dir,
             python_version: self.python_version,
         })
     }

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

@@ -29,7 +29,7 @@ pub fn install_wheel(
     wheel: impl AsRef<Path>,
     link_mode: LinkMode,
 ) -> Result<(), Error> {
-    let base_location = location.venv_base();
+    let root = location.venv_root();
 
     // TODO(charlie): Pass this in.
     let site_packages_python = format!(
@@ -38,10 +38,9 @@ pub fn install_wheel(
         location.python_version().1
     );
     let site_packages = if cfg!(target_os = "windows") {
-        base_location.as_ref().join("Lib").join("site-packages")
+        root.as_ref().join("Lib").join("site-packages")
     } else {
-        base_location
-            .as_ref()
+        root.as_ref()
             .join("lib")
             .join(site_packages_python)
             .join("site-packages")
@@ -88,7 +87,7 @@ pub fn install_wheel(
     if data_dir.is_dir() {
         debug!(name, "Installing data");
         install_data(
-            base_location.as_ref(),
+            root.as_ref(),
             &site_packages,
             &data_dir,
             &name,

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

@@ -722,7 +722,7 @@ fn install_script(
 /// Move the files from the .data directory to the right location in the venv
 #[allow(clippy::too_many_arguments)]
 pub(crate) fn install_data(
-    venv_base: &Path,
+    venv_root: &Path,
     site_packages: &Path,
     data_dir: &Path,
     dist_name: &str,
@@ -736,7 +736,7 @@ pub(crate) fn install_data(
         match data_entry.file_name().as_os_str().to_str() {
             Some("data") => {
                 // Move the content of the folder to the root of the venv
-                move_folder_recorded(&data_entry.path(), venv_base, site_packages, record)?;
+                move_folder_recorded(&data_entry.path(), venv_root, site_packages, record)?;
             }
             Some("scripts") => {
                 for file in fs::read_dir(data_entry.path())? {
@@ -762,7 +762,7 @@ pub(crate) fn install_data(
                 }
             }
             Some("headers") => {
-                let target_path = venv_base
+                let target_path = venv_root
                     .join("include")
                     .join("site")
                     .join(format!(
@@ -901,7 +901,7 @@ pub fn install_wheel(
     let name = &filename.distribution;
     let _my_span = span!(Level::DEBUG, "install_wheel", name = name.as_str());
 
-    let base_location = location.venv_base();
+    let base_location = location.venv_root();
 
     let site_packages_python = format!(
         "python{}.{}",