Use separate path types for directories and files (#4285)

## Summary

This is what I consider to be the "real" fix for #8072. We now treat
directory and path URLs as separate `ParsedUrl` types and
`RequirementSource` types. This removes a lot of `.is_dir()` forking
within the `ParsedUrl::Path` arms and makes some states impossible
(e.g., you can't have a `.whl` path that is editable). It _also_ fixes
the `direct_url.json` for direct URLs that refer to files. Previously,
we wrote out to these as if they were installed as directories, which is
just wrong.

crates/distribution-types/src/cached.rs

@@ -4,7 +4,7 @@ use anyhow::{anyhow, Result};
 
 use distribution_filename::WheelFilename;
 use pep508_rs::VerbatimUrl;
-use pypi_types::{HashDigest, ParsedPathUrl};
+use pypi_types::{HashDigest, ParsedDirectoryUrl};
 use uv_normalize::PackageName;
 
 use crate::{
@@ -120,7 +120,7 @@ impl CachedDist {
                         .url
                         .to_file_path()
                         .map_err(|()| anyhow!("Invalid path in file URL"))?;
-                    Ok(Some(ParsedUrl::Path(ParsedPathUrl {
+                    Ok(Some(ParsedUrl::Directory(ParsedDirectoryUrl {
                         url: dist.url.raw().clone(),
                         install_path: path.clone(),
                         lock_path: path,

crates/distribution-types/src/error.rs

@@ -1,6 +1,5 @@
 use url::Url;
 
-use pep508_rs::VerbatimUrl;
 use uv_normalize::PackageName;
 
 #[derive(thiserror::Error, Debug)]
@@ -14,21 +13,12 @@ pub enum Error {
     #[error(transparent)]
     WheelFilename(#[from] distribution_filename::WheelFilenameError),
 
-    #[error("Unable to extract file path from URL: {0}")]
-    MissingFilePath(Url),
-
     #[error("Could not extract path segments from URL: {0}")]
     MissingPathSegments(Url),
 
     #[error("Distribution not found at: {0}")]
     NotFound(Url),
 
-    #[error("Unsupported scheme `{0}` on URL: {1} ({2})")]
-    UnsupportedScheme(String, String, String),
-
     #[error("Requested package name `{0}` does not match `{1}` in the distribution filename: {2}")]
     PackageNameMismatch(PackageName, PackageName, String),
-
-    #[error("Only directories can be installed as editable, not filenames: `{0}`")]
-    EditableFile(VerbatimUrl),
 }

crates/distribution-types/src/lib.rs

@@ -329,7 +329,6 @@ impl Dist {
         url: VerbatimUrl,
         install_path: &Path,
         lock_path: &Path,
-        editable: bool,
     ) -> Result<Dist, Error> {
         // Store the canonicalized path, which also serves to validate that it exists.
         let canonicalized_path = match install_path.canonicalize() {
@@ -340,16 +339,8 @@ impl Dist {
             Err(err) => return Err(err.into()),
         };
 
-        // Determine whether the path represents an archive or a directory.
-        if canonicalized_path.is_dir() {
-            Ok(Self::Source(SourceDist::Directory(DirectorySourceDist {
-                name,
-                install_path: canonicalized_path.clone(),
-                lock_path: lock_path.to_path_buf(),
-                editable,
-                url,
-            })))
-        } else if canonicalized_path
+        // Determine whether the path represents a built or source distribution.
+        if canonicalized_path
             .extension()
             .is_some_and(|ext| ext.eq_ignore_ascii_case("whl"))
         {
@@ -362,30 +353,48 @@ impl Dist {
                     url.verbatim().to_string(),
                 ));
             }
-
-            if editable {
-                return Err(Error::EditableFile(url));
-            }
-
             Ok(Self::Built(BuiltDist::Path(PathBuiltDist {
                 filename,
                 path: canonicalized_path,
                 url,
             })))
         } else {
-            if editable {
-                return Err(Error::EditableFile(url));
-            }
-
             Ok(Self::Source(SourceDist::Path(PathSourceDist {
                 name,
                 install_path: canonicalized_path.clone(),
-                lock_path: canonicalized_path,
+                lock_path: lock_path.to_path_buf(),
                 url,
             })))
         }
     }
 
+    /// A local source tree from a `file://` URL.
+    pub fn from_directory_url(
+        name: PackageName,
+        url: VerbatimUrl,
+        install_path: &Path,
+        lock_path: &Path,
+        editable: bool,
+    ) -> Result<Dist, Error> {
+        // Store the canonicalized path, which also serves to validate that it exists.
+        let canonicalized_path = match install_path.canonicalize() {
+            Ok(path) => path,
+            Err(err) if err.kind() == std::io::ErrorKind::NotFound => {
+                return Err(Error::NotFound(url.to_url()));
+            }
+            Err(err) => return Err(err.into()),
+        };
+
+        // Determine whether the path represents an archive or a directory.
+        Ok(Self::Source(SourceDist::Directory(DirectorySourceDist {
+            name,
+            install_path: canonicalized_path.clone(),
+            lock_path: lock_path.to_path_buf(),
+            editable,
+            url,
+        })))
+    }
+
     /// A remote source distribution from a `git+https://` or `git+ssh://` url.
     pub fn from_git_url(
         name: PackageName,
@@ -407,12 +416,15 @@ impl Dist {
             ParsedUrl::Archive(archive) => {
                 Self::from_http_url(name, url.verbatim, archive.url, archive.subdirectory)
             }
-            ParsedUrl::Path(file) => Self::from_file_url(
+            ParsedUrl::Path(file) => {
+                Self::from_file_url(name, url.verbatim, &file.install_path, &file.lock_path)
+            }
+            ParsedUrl::Directory(directory) => Self::from_directory_url(
                 name,
                 url.verbatim,
-                &file.install_path,
-                &file.lock_path,
-                file.editable,
+                &directory.install_path,
+                &directory.lock_path,
+                directory.editable,
             ),
             ParsedUrl::Git(git) => {
                 Self::from_git_url(name, url.verbatim, git.url, git.subdirectory)

crates/distribution-types/src/resolution.rs

@@ -144,7 +144,6 @@ impl From<&ResolvedDist> for Requirement {
                     install_path: wheel.path.clone(),
                     lock_path: wheel.path.clone(),
                     url: wheel.url.clone(),
-                    editable: false,
                 },
                 Dist::Source(SourceDist::Registry(sdist)) => RequirementSource::Registry {
                     specifier: pep440_rs::VersionSpecifiers::from(
@@ -172,9 +171,8 @@ impl From<&ResolvedDist> for Requirement {
                     install_path: sdist.install_path.clone(),
                     lock_path: sdist.lock_path.clone(),
                     url: sdist.url.clone(),
-                    editable: false,
                 },
-                Dist::Source(SourceDist::Directory(sdist)) => RequirementSource::Path {
+                Dist::Source(SourceDist::Directory(sdist)) => RequirementSource::Directory {
                     install_path: sdist.install_path.clone(),
                     lock_path: sdist.lock_path.clone(),
                     url: sdist.url.clone(),