Make missing METADATA file a recoverable error (#4247)

## Summary

I don't have a great way to test it, but this makes the error described
in https://github.com/astral-sh/uv/issues/4246 an incompatibility rather
than a fatal error.

Closes https://github.com/astral-sh/uv/issues/4246.

Cargo.lock

@@ -4544,7 +4544,6 @@ dependencies = [
  "serde",
  "serde_json",
  "sys-info",
- "tempfile",
  "thiserror",
  "tl",
  "tokio",

crates/uv-client/Cargo.toml

@@ -38,7 +38,6 @@ rmp-serde = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 sys-info = { workspace = true }
-tempfile = { workspace = true }
 thiserror = { workspace = true }
 tl = { workspace = true }
 tokio = { workspace = true }

crates/uv-client/src/error.rs

@@ -162,10 +162,6 @@ pub enum ErrorKind {
     #[error("Metadata file `{0}` was not found in {1}")]
     MetadataNotFound(WheelFilename, String),
 
-    /// The metadata file was not found in the registry.
-    #[error("File `{0}` was not found in the registry at {1}.")]
-    FileNotFound(String, #[source] BetterReqwestError),
-
     /// A generic request error happened while making a request. Refer to the
     /// error message for more details.
     #[error(transparent)]
@@ -185,9 +181,6 @@ pub enum ErrorKind {
     #[error(transparent)]
     AsyncHttpRangeReader(#[from] AsyncHttpRangeReaderError),
 
-    #[error("Expected a single .dist-info directory in {0}, found {1}")]
-    InvalidDistInfo(WheelFilename, String),
-
     #[error("{0} is not a valid wheel filename")]
     WheelFilename(#[source] WheelFilenameError),
 
@@ -212,10 +205,6 @@ pub enum ErrorKind {
     #[error("Cache serialization failed")]
     Encode(#[source] rmp_serde::encode::Error),
 
-    /// An [`io::Error`] with a filename attached
-    #[error(transparent)]
-    Persist(#[from] tempfile::PersistError),
-
     #[error("Missing `Content-Type` header for {0}")]
     MissingContentType(Url),
 

crates/uv-resolver/src/pubgrub/report.rs

@@ -476,6 +476,11 @@ impl PubGrubReportFormatter<'_> {
                                 Some(UnavailablePackage::Offline) => {
                                     hints.insert(PubGrubHint::Offline);
                                 }
+                                Some(UnavailablePackage::MissingMetadata) => {
+                                    hints.insert(PubGrubHint::MissingPackageMetadata {
+                                        package: package.clone(),
+                                    });
+                                }
                                 Some(UnavailablePackage::InvalidMetadata(reason)) => {
                                     hints.insert(PubGrubHint::InvalidPackageMetadata {
                                         package: package.clone(),
@@ -500,6 +505,12 @@ impl PubGrubReportFormatter<'_> {
                                             IncompletePackage::Offline => {
                                                 hints.insert(PubGrubHint::Offline);
                                             }
+                                            IncompletePackage::MissingMetadata => {
+                                                hints.insert(PubGrubHint::MissingVersionMetadata {
+                                                    package: package.clone(),
+                                                    version: version.clone(),
+                                                });
+                                            }
                                             IncompletePackage::InvalidMetadata(reason) => {
                                                 hints.insert(PubGrubHint::InvalidVersionMetadata {
                                                     package: package.clone(),
@@ -601,6 +612,8 @@ pub(crate) enum PubGrubHint {
     NoIndex,
     /// A package was not found in the registry, but network access was disabled.
     Offline,
+    /// Metadata for a package could not be found.
+    MissingPackageMetadata { package: PubGrubPackage },
     /// Metadata for a package could not be parsed.
     InvalidPackageMetadata {
         package: PubGrubPackage,
@@ -613,6 +626,12 @@ pub(crate) enum PubGrubHint {
         #[derivative(PartialEq = "ignore", Hash = "ignore")]
         reason: String,
     },
+    /// Metadata for a package version could not be found.
+    MissingVersionMetadata {
+        package: PubGrubPackage,
+        #[derivative(PartialEq = "ignore", Hash = "ignore")]
+        version: Version,
+    },
     /// Metadata for a package version could not be parsed.
     InvalidVersionMetadata {
         package: PubGrubPackage,
@@ -689,6 +708,15 @@ impl std::fmt::Display for PubGrubHint {
                     ":".bold(),
                 )
             }
+            Self::MissingPackageMetadata { package } => {
+                write!(
+                    f,
+                    "{}{} Metadata for {} could not be found, as the wheel is missing a `METADATA` file",
+                    "hint".bold().cyan(),
+                    ":".bold(),
+                    package.bold()
+                )
+            }
             Self::InvalidPackageMetadata { package, reason } => {
                 write!(
                     f,
@@ -709,6 +737,16 @@ impl std::fmt::Display for PubGrubHint {
                     textwrap::indent(reason, "  ")
                 )
             }
+            Self::MissingVersionMetadata { package, version } => {
+                write!(
+                    f,
+                    "{}{} Metadata for {}=={} could not be found, as the wheel is missing a `METADATA` file",
+                    "hint".bold().cyan(),
+                    ":".bold(),
+                    package.bold(),
+                    version.bold(),
+                )
+            }
             Self::InvalidVersionMetadata {
                 package,
                 version,

crates/uv-resolver/src/resolver/availability.rs

@@ -30,6 +30,8 @@ impl Display for UnavailableReason {
 pub(crate) enum UnavailableVersion {
     /// Version is incompatible because it has no usable distributions
     IncompatibleDist(IncompatibleDist),
+    /// The wheel metadata was not found.
+    MissingMetadata,
     /// The wheel metadata was found, but could not be parsed.
     InvalidMetadata,
     /// The wheel metadata was found, but the metadata was inconsistent.
@@ -46,6 +48,9 @@ impl Display for UnavailableVersion {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         match self {
             UnavailableVersion::IncompatibleDist(invalid_dist) => Display::fmt(invalid_dist, f),
+            UnavailableVersion::MissingMetadata => {
+                f.write_str("does not include a `METADATA` file")
+            }
             UnavailableVersion::InvalidMetadata => f.write_str("has invalid metadata"),
             UnavailableVersion::InconsistentMetadata => f.write_str("has inconsistent metadata"),
             UnavailableVersion::InvalidStructure => f.write_str("has an invalid package format"),
@@ -66,6 +71,8 @@ pub(crate) enum UnavailablePackage {
     Offline,
     /// The package was not found in the registry.
     NotFound,
+    /// The package metadata was not found.
+    MissingMetadata,
     /// The package metadata was found, but could not be parsed.
     InvalidMetadata(String),
     /// The package has an invalid structure.
@@ -78,6 +85,7 @@ impl UnavailablePackage {
             UnavailablePackage::NoIndex => "was not found in the provided package locations",
             UnavailablePackage::Offline => "was not found in the cache",
             UnavailablePackage::NotFound => "was not found in the package registry",
+            UnavailablePackage::MissingMetadata => "does not include a `METADATA` file",
             UnavailablePackage::InvalidMetadata(_) => "has invalid metadata",
             UnavailablePackage::InvalidStructure(_) => "has an invalid package format",
         }
@@ -95,6 +103,8 @@ impl Display for UnavailablePackage {
 pub(crate) enum IncompletePackage {
     /// Network requests were disabled (i.e., `--offline`), and the wheel metadata was not found in the cache.
     Offline,
+    /// The wheel metadata was not found.
+    MissingMetadata,
     /// The wheel metadata was found, but could not be parsed.
     InvalidMetadata(String),
     /// The wheel metadata was found, but the metadata was inconsistent.

crates/uv-resolver/src/resolver/mod.rs

@@ -749,6 +749,11 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
                             .insert(name.clone(), UnavailablePackage::Offline);
                         return Ok(None);
                     }
+                    MetadataResponse::MissingMetadata => {
+                        self.unavailable_packages
+                            .insert(name.clone(), UnavailablePackage::MissingMetadata);
+                        return Ok(None);
+                    }
                     MetadataResponse::InvalidMetadata(err) => {
                         self.unavailable_packages.insert(
                             name.clone(),
@@ -1042,6 +1047,15 @@ impl<InstalledPackages: InstalledPackagesProvider> ResolverState<InstalledPackag
                             .insert(version.clone(), IncompletePackage::Offline);
                         return Ok(Dependencies::Unavailable(UnavailableVersion::Offline));
                     }
+                    MetadataResponse::MissingMetadata => {
+                        self.incomplete_packages
+                            .entry(name.clone())
+                            .or_default()
+                            .insert(version.clone(), IncompletePackage::MissingMetadata);
+                        return Ok(Dependencies::Unavailable(
+                            UnavailableVersion::MissingMetadata,
+                        ));
+                    }
                     MetadataResponse::InvalidMetadata(err) => {
                         warn!("Unable to extract metadata for {name}: {err}");
                         self.incomplete_packages

crates/uv-resolver/src/resolver/provider.rs

@@ -33,6 +33,8 @@ pub enum VersionsResponse {
 pub enum MetadataResponse {
     /// The wheel metadata was found and parsed successfully.
     Found(ArchiveMetadata),
+    /// The wheel metadata was not found.
+    MissingMetadata,
     /// The wheel metadata was found, but could not be parsed.
     InvalidMetadata(Box<pypi_types::MetadataError>),
     /// The wheel metadata was found, but the metadata was inconsistent.
@@ -184,6 +186,9 @@ impl<'a, Context: BuildContext> ResolverProvider for DefaultResolverProvider<'a,
             Err(err) => match err {
                 uv_distribution::Error::Client(client) => match client.into_kind() {
                     uv_client::ErrorKind::Offline(_) => Ok(MetadataResponse::Offline),
+                    uv_client::ErrorKind::MetadataNotFound(_, _) => {
+                        Ok(MetadataResponse::MissingMetadata)
+                    }
                     uv_client::ErrorKind::MetadataParseError(_, _, err) => {
                         Ok(MetadataResponse::InvalidMetadata(err))
                     }