Ignore invalid extra named .none (#1428)

## Summary

Some packages erroneously include an extra named `.none`. It turns out
that certain versions of `flit` included this by accident:
https://github.com/pypa/flit/issues/228/.

This PR adds leniency for that specific extra name.

Closes https://github.com/astral-sh/uv/issues/1363.

Closes https://github.com/astral-sh/uv/issues/1399.

crates/pypi-types/src/lenient_requirement.rs

@@ -7,6 +7,7 @@ use tracing::warn;
 
 use pep440_rs::{VersionSpecifiers, VersionSpecifiersParseError};
 use pep508_rs::{Pep508Error, Requirement};
+use uv_normalize::{ExtraName, InvalidNameError};
 
 /// Ex) `>=7.2.0<8.0.0`
 static MISSING_COMMA: Lazy<Regex> = Lazy::new(|| Regex::new(r"(\d)([<>=~^!])").unwrap());
@@ -122,6 +123,36 @@ impl<'de> Deserialize<'de> for LenientVersionSpecifiers {
     }
 }
 
+#[derive(Debug, Clone)]
+pub struct LenientExtraName(ExtraName);
+
+impl LenientExtraName {
+    /// Parse an [`ExtraName`] from a string, but return `None` if the name is `.none`.
+    ///
+    /// Some versions of `flit` erroneously included `.none` as an extra name, which is not
+    /// allowed by PEP 508.
+    ///
+    /// See: <https://github.com/pypa/flit/issues/228/>
+    pub fn try_parse(name: String) -> Option<Result<Self, InvalidNameError>> {
+        match ExtraName::new(name) {
+            Ok(name) => Some(Ok(Self(name))),
+            Err(err) => {
+                if err.as_str() == ".none" {
+                    None
+                } else {
+                    Some(Err(err))
+                }
+            }
+        }
+    }
+}
+
+impl From<LenientExtraName> for ExtraName {
+    fn from(name: LenientExtraName) -> Self {
+        name.0
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::str::FromStr;

crates/pypi-types/src/metadata.rs

@@ -12,7 +12,7 @@ use pep508_rs::{Pep508Error, Requirement};
 use uv_normalize::{ExtraName, InvalidNameError, PackageName};
 
 use crate::lenient_requirement::LenientRequirement;
-use crate::LenientVersionSpecifiers;
+use crate::{LenientExtraName, LenientVersionSpecifiers};
 
 /// Python Package Metadata 2.1 as specified in
 /// <https://packaging.python.org/specifications/core-metadata/>.
@@ -119,7 +119,11 @@ impl Metadata21 {
             })
             .transpose()?;
         let provides_extras = get_all_values("Provides-Extra")
-            .map(ExtraName::new)
+            .filter_map(LenientExtraName::try_parse)
+            .map(|result| match result {
+                Ok(extra_name) => Ok(ExtraName::from(extra_name)),
+                Err(err) => Err(err),
+            })
             .collect::<Result<Vec<_>, _>>()?;
 
         Ok(Metadata21 {