Always treat archive-like requirements as local files (#7364)

## Summary

`uv pip install foo.tar.gz` will now always treat `foo.tar.gz` as a
local file. This matches pip's behavior.

Closes #7309.

crates/pep508-rs/src/lib.rs

@@ -657,8 +657,13 @@ fn looks_like_unnamed_requirement(cursor: &mut Cursor) -> bool {
     // Expand any environment variables in the path.
     let expanded = expand_env_vars(url);
 
+    // Strip extras.
+    let url = split_extras(&expanded)
+        .map(|(url, _)| url)
+        .unwrap_or(&expanded);
+
     // Analyze the path.
-    let mut chars = expanded.chars();
+    let mut chars = url.chars();
 
     let Some(first_char) = chars.next() else {
         return false;
@@ -670,18 +675,47 @@ fn looks_like_unnamed_requirement(cursor: &mut Cursor) -> bool {
     }
 
     // Ex) `https://` or `C:`
-    if split_scheme(&expanded).is_some() {
+    if split_scheme(url).is_some() {
         return true;
     }
 
     // Ex) `foo/bar`
-    if expanded.contains('/') || expanded.contains('\\') {
+    if url.contains('/') || url.contains('\\') {
+        return true;
+    }
+
+    // Ex) `foo.tar.gz`
+    if looks_like_archive(url) {
         return true;
     }
 
     false
 }
 
+/// Returns `true` if a file looks like an archive.
+///
+/// See <https://github.com/pypa/pip/blob/111eed14b6e9fba7c78a5ec2b7594812d17b5d2b/src/pip/_internal/utils/filetypes.py#L8>
+/// for the list of supported archive extensions.
+fn looks_like_archive(file: impl AsRef<Path>) -> bool {
+    let file = file.as_ref();
+
+    // E.g., `gz` in `foo.tar.gz`
+    let Some(extension) = file.extension().and_then(|ext| ext.to_str()) else {
+        return false;
+    };
+
+    // E.g., `tar` in `foo.tar.gz`
+    let pre_extension = file
+        .file_stem()
+        .and_then(|stem| Path::new(stem).extension().and_then(|ext| ext.to_str()));
+
+    matches!(
+        (pre_extension, extension),
+        (_, "whl" | "tbz" | "txz" | "tlz" | "zip" | "tgz" | "tar")
+            | (Some("tar"), "bz2" | "xz" | "lz" | "lzma" | "gz")
+    )
+}
+
 /// parses extras in the `[extra1,extra2] format`
 fn parse_extras_cursor<T: Pep508Url>(
     cursor: &mut Cursor,
@@ -970,7 +1004,9 @@ fn parse_pep508_requirement<T: Pep508Url>(
     // wsp*
     cursor.eat_whitespace();
     // name
+    let name_start = cursor.pos();
     let name = parse_name(cursor)?;
+    let name_end = cursor.pos();
     // wsp*
     cursor.eat_whitespace();
     // extras?
@@ -1018,6 +1054,23 @@ fn parse_pep508_requirement<T: Pep508Url>(
 
     let requirement_end = cursor.pos();
 
+    // If the requirement consists solely of a package name, and that name appears to be an archive,
+    // treat it as a URL requirement, for consistency and security. (E.g., `requests-2.26.0.tar.gz`
+    // is a valid Python package name, but we should treat it as a reference to a file.)
+    //
+    // See: https://github.com/pypa/pip/blob/111eed14b6e9fba7c78a5ec2b7594812d17b5d2b/src/pip/_internal/utils/filetypes.py#L8
+    if requirement_kind.is_none() {
+        if looks_like_archive(cursor.slice(name_start, name_end)) {
+            let clone = cursor.clone().at(start);
+            return Err(Pep508Error {
+                message: Pep508ErrorSource::UnsupportedRequirement("URL requirement must be preceded by a package name. Add the name of the package before the URL (e.g., `package_name @ https://...`).".to_string()),
+                start,
+                len: clone.pos() - start,
+                input: clone.to_string(),
+            });
+        }
+    }
+
     // wsp*
     cursor.eat_whitespace();
     // quoted_marker?