Allow unknown preview flags with a warning again

crates/uv-cli/src/lib.rs

@@ -24,7 +24,7 @@ use uv_distribution_types::{
 };
 use uv_normalize::{ExtraName, GroupName, PackageName, PipGroupName};
 use uv_pep508::{MarkerTree, Requirement};
-use uv_preview::PreviewFeature;
+use uv_preview::MaybePreviewFeature;
 use uv_pypi_types::VerbatimParsedUrl;
 use uv_python::{PythonDownloads, PythonPreference, PythonVersion};
 use uv_redacted::DisplaySafeUrl;
@@ -326,9 +326,8 @@ pub struct GlobalArgs {
         value_delimiter = ',',
         hide = true,
         alias = "preview-feature",
-        value_enum,
     )]
-    pub preview_features: Vec<PreviewFeature>,
+    pub preview_features: Vec<MaybePreviewFeature>,
 
     /// Avoid discovering a `pyproject.toml` or `uv.toml` file [env: UV_ISOLATED=]
     ///

crates/uv-preview/src/lib.rs

@@ -354,6 +354,33 @@ impl FromStr for PreviewFeature {
     }
 }
 
+#[derive(Debug, Error, Clone, Copy, PartialEq, Eq)]
+#[error("preview feature name cannot be empty")]
+pub struct EmptyPreviewFeatureNameError;
+
+/// A user-provided preview feature name, which may refer to an unknown feature.
+#[derive(Debug, Clone)]
+pub enum MaybePreviewFeature {
+    Known(PreviewFeature),
+    Unknown(String),
+}
+
+impl FromStr for MaybePreviewFeature {
+    type Err = EmptyPreviewFeatureNameError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let s = s.trim();
+        if s.is_empty() {
+            return Err(EmptyPreviewFeatureNameError);
+        }
+
+        Ok(match PreviewFeature::from_str(s) {
+            Ok(feature) => Self::Known(feature),
+            Err(_) => Self::Unknown(s.to_string()),
+        })
+    }
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, Default)]
 pub struct Preview {
     flags: BitFlags<PreviewFeature>,
@@ -379,7 +406,12 @@ impl Preview {
         }
     }
 
-    pub fn from_args(preview: bool, no_preview: bool, preview_features: &[PreviewFeature]) -> Self {
+    /// Resolve preview arguments, warning and ignoring unknown feature names.
+    pub fn from_args(
+        preview: bool,
+        no_preview: bool,
+        preview_features: &[MaybePreviewFeature],
+    ) -> Self {
         if no_preview {
             return Self::default();
         }
@@ -388,7 +420,7 @@ impl Preview {
             return Self::all();
         }
 
-        Self::new(preview_features)
+        Self::from_feature_names(preview_features)
     }
 
     /// Check if a single feature is enabled.
@@ -405,6 +437,23 @@ impl Preview {
     pub fn any_enabled(&self) -> bool {
         !self.flags.is_empty()
     }
+
+    fn from_feature_names<'a>(
+        feature_names: impl IntoIterator<Item = &'a MaybePreviewFeature>,
+    ) -> Self {
+        let mut flags = BitFlags::empty();
+
+        for feature_name in feature_names {
+            match feature_name {
+                MaybePreviewFeature::Known(feature) => flags |= *feature,
+                MaybePreviewFeature::Unknown(feature_name) => {
+                    warn_user_once!("Unknown preview feature: `{feature_name}`");
+                }
+            }
+        }
+
+        Self { flags }
+    }
 }
 
 impl Display for Preview {
@@ -423,35 +472,16 @@ impl Display for Preview {
     }
 }
 
-#[derive(Debug, Error, Clone)]
-pub enum PreviewParseError {
-    #[error("Empty string in preview features: {0}")]
-    Empty(String),
-}
-
 impl FromStr for Preview {
-    type Err = PreviewParseError;
+    type Err = EmptyPreviewFeatureNameError;
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let mut flags = BitFlags::empty();
-
-        for part in s.split(',') {
-            let part = part.trim();
-            if part.is_empty() {
-                return Err(PreviewParseError::Empty(
-                    "Empty string in preview features".to_string(),
-                ));
-            }
+        let feature_names = s
+            .split(',')
+            .map(MaybePreviewFeature::from_str)
+            .collect::<Result<Vec<_>, _>>()?;
 
-            match PreviewFeature::from_str(part) {
-                Ok(flag) => flags |= flag,
-                Err(_) => {
-                    warn_user_once!("Unknown preview feature: `{part}`");
-                }
-            }
-        }
-
-        Ok(Self { flags })
+        Ok(Self::from_feature_names(&feature_names))
     }
 }
 
@@ -483,7 +513,7 @@ mod tests {
         assert!(preview.is_enabled(PreviewFeature::AddBounds));
 
         // Test empty string error
-        assert!(Preview::from_str("").is_err());
+        assert_eq!(Preview::from_str(""), Err(EmptyPreviewFeatureNameError));
         assert!(Preview::from_str("pylock,").is_err());
         assert!(Preview::from_str(",pylock").is_err());
 
@@ -529,11 +559,17 @@ mod tests {
         assert_eq!(preview.to_string(), "enabled");
 
         // Test specific features
-        let features = vec![PreviewFeature::PythonUpgrade, PreviewFeature::JsonOutput];
+        let features = ["python-upgrade", "json-output"].map(|name| name.parse().unwrap());
         let preview = Preview::from_args(false, false, &features);
         assert!(preview.is_enabled(PreviewFeature::PythonUpgrade));
         assert!(preview.is_enabled(PreviewFeature::JsonOutput));
         assert!(!preview.is_enabled(PreviewFeature::Pylock));
+
+        // Test unknown features
+        let features = ["unknown-feature", "pylock"].map(|name| name.parse().unwrap());
+        let preview = Preview::from_args(false, false, &features);
+        assert!(preview.is_enabled(PreviewFeature::Pylock));
+        assert_eq!(preview.flags.bits().count_ones(), 1);
     }
 
     #[test]

crates/uv/tests/it/show_settings.rs

@@ -2967,6 +2967,44 @@ fn preview_features() {
     "
     );
 
+    diff_uv_snapshot!(
+        context.filters(),
+        &preview_features,
+        add_shared_args(context.version())
+            .arg("--show-settings")
+            .arg("--preview-features")
+            .arg("python-install-default,unknown-preview-feature,python-upgrade"),
+        @"
+    --- old
+    +++ new
+    @@ -122,3 +122,4 @@
+     }
+
+     ----- stderr -----
+    +warning: Unknown preview feature: `unknown-preview-feature`
+    "
+    );
+
+    diff_uv_snapshot!(
+        context.filters(),
+        &preview_features,
+        add_shared_args(context.version())
+            .arg("--show-settings")
+            .env(
+                EnvVars::UV_PREVIEW_FEATURES,
+                "python-install-default,unknown-preview-feature,python-upgrade",
+            ),
+        @"
+    --- old
+    +++ new
+    @@ -122,3 +122,4 @@
+     }
+
+     ----- stderr -----
+    +warning: Unknown preview feature: `unknown-preview-feature`
+    "
+    );
+
     // Compare against output with both features passed to one `--preview-features` option.
     diff_uv_snapshot!(context.filters(), &preview_features, add_shared_args(context.version()).arg("--show-settings").arg("--preview-features").arg("python-install-default").arg("--preview-feature").arg("python-upgrade"), @""
     );
@@ -2979,6 +3017,44 @@ fn preview_features() {
         .arg("--no-preview"),
         @""
     );
+
+    uv_snapshot!(
+        context.filters(),
+        add_shared_args(context.version())
+            .arg("--show-settings")
+            .arg("--preview-features")
+            .arg("python-install-default,,python-upgrade"),
+        @"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: invalid value '' for '--preview-features <PREVIEW_FEATURES>': preview feature name cannot be empty
+
+    For more information, try '--help'.
+    "
+    );
+
+    uv_snapshot!(
+        context.filters(),
+        add_shared_args(context.version())
+            .arg("--show-settings")
+            .env(
+                EnvVars::UV_PREVIEW_FEATURES,
+                "python-install-default,,python-upgrade",
+            ),
+        @"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: invalid value '' for '--preview-features <PREVIEW_FEATURES>': preview feature name cannot be empty
+
+    For more information, try '--help'.
+    "
+    );
 }
 
 #[test]