Use serde-untagged to improve some untagged enum error messages

Cargo.toml

@@ -141,6 +141,7 @@ same-file = { version = "1.0.6" }
 schemars = { version = "0.8.21", features = ["url"] }
 seahash = { version = "4.1.0" }
 serde = { version = "1.0.210", features = ["derive"] }
+serde-untagged = { version = "0.1.6" }
 serde_json = { version = "1.0.128" }
 sha2 = { version = "0.10.8" }
 smallvec = { version = "1.13.2" }

crates/pypi-types/Cargo.toml

@@ -27,6 +27,7 @@ mailparse = { workspace = true }
 regex = { workspace = true }
 rkyv = { workspace = true }
 serde = { workspace = true }
+serde-untagged = { workspace = true }
 thiserror = { workspace = true }
 toml = { workspace = true }
 toml_edit = { workspace = true }

crates/pypi-types/src/simple_json.rs

@@ -1,9 +1,8 @@
 use std::str::FromStr;
 
 use jiff::Timestamp;
-use serde::{Deserialize, Deserializer, Serialize};
-
 use pep440_rs::{VersionSpecifiers, VersionSpecifiersParseError};
+use serde::{Deserialize, Deserializer, Serialize};
 
 use crate::lenient_requirement::LenientVersionSpecifiers;
 
@@ -71,13 +70,24 @@ where
     ))
 }
 
-#[derive(Debug, Clone, Deserialize)]
-#[serde(untagged)]
+#[derive(Debug, Clone)]
 pub enum CoreMetadata {
     Bool(bool),
     Hashes(Hashes),
 }
 
+impl<'de> Deserialize<'de> for CoreMetadata {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        serde_untagged::UntaggedEnumVisitor::new()
+            .bool(|bool| Ok(CoreMetadata::Bool(bool)))
+            .map(|map| map.deserialize().map(CoreMetadata::Hashes))
+            .deserialize(deserializer)
+    }
+}
+
 impl CoreMetadata {
     pub fn is_available(&self) -> bool {
         match self {
@@ -87,24 +97,25 @@ impl CoreMetadata {
     }
 }
 
-#[derive(
-    Debug,
-    Clone,
-    PartialEq,
-    Eq,
-    Hash,
-    Deserialize,
-    rkyv::Archive,
-    rkyv::Deserialize,
-    rkyv::Serialize,
-)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash, rkyv::Archive, rkyv::Deserialize, rkyv::Serialize)]
 #[rkyv(derive(Debug))]
-#[serde(untagged)]
 pub enum Yanked {
     Bool(bool),
     Reason(String),
 }
 
+impl<'de> Deserialize<'de> for Yanked {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        serde_untagged::UntaggedEnumVisitor::new()
+            .bool(|bool| Ok(Yanked::Bool(bool)))
+            .string(|string| Ok(Yanked::Reason(string.to_owned())))
+            .deserialize(deserializer)
+    }
+}
+
 impl Yanked {
     pub fn is_yanked(&self) -> bool {
         match self {

crates/uv-configuration/Cargo.toml

@@ -28,6 +28,7 @@ fs-err = { workspace = true }
 rustc-hash = { workspace = true }
 schemars = { workspace = true, optional = true }
 serde = { workspace = true }
+serde-untagged = { workspace = true }
 serde_json = { workspace = true }
 thiserror = { workspace = true }
 tracing = { workspace = true }

crates/uv-configuration/src/trusted_host.rs

@@ -1,5 +1,5 @@
+use serde::{Deserialize, Deserializer};
 use std::str::FromStr;
-
 use url::Url;
 
 /// A trusted host, which could be a host or a host-port pair.
@@ -33,28 +33,28 @@ impl TrustedHost {
     }
 }
 
-#[derive(serde::Deserialize)]
-#[serde(untagged)]
-enum TrustHostWire {
-    String(String),
-    Struct {
-        scheme: Option<String>,
-        host: String,
-        port: Option<u16>,
-    },
-}
-
-impl<'de> serde::de::Deserialize<'de> for TrustedHost {
-    fn deserialize<D>(deserializer: D) -> Result<TrustedHost, D::Error>
+impl<'de> Deserialize<'de> for TrustedHost {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
-        D: serde::de::Deserializer<'de>,
+        D: Deserializer<'de>,
     {
-        let helper = TrustHostWire::deserialize(deserializer)?;
-
-        match helper {
-            TrustHostWire::String(s) => TrustedHost::from_str(&s).map_err(serde::de::Error::custom),
-            TrustHostWire::Struct { scheme, host, port } => Ok(TrustedHost { scheme, host, port }),
+        #[derive(Deserialize)]
+        struct Inner {
+            scheme: Option<String>,
+            host: String,
+            port: Option<u16>,
         }
+
+        serde_untagged::UntaggedEnumVisitor::new()
+            .string(|string| TrustedHost::from_str(string).map_err(serde::de::Error::custom))
+            .map(|map| {
+                map.deserialize::<Inner>().map(|inner| TrustedHost {
+                    scheme: inner.scheme,
+                    host: inner.host,
+                    port: inner.port,
+                })
+            })
+            .deserialize(deserializer)
     }
 }
 

crates/uv-distribution/src/metadata/requires_dist.rs

@@ -226,6 +226,29 @@ mod test {
         "###);
     }
 
+    #[tokio::test]
+    async fn wrong_type() {
+        let input = indoc! {r#"
+            [project]
+            name = "foo"
+            version = "0.0.0"
+            dependencies = [
+              "tqdm",
+            ]
+            [tool.uv.sources]
+            tqdm = true
+        "#};
+
+        assert_snapshot!(format_err(input).await, @r###"
+        error: TOML parse error at line 8, column 8
+          |
+        8 | tqdm = true
+          |        ^^^^
+        invalid type: boolean `true`, expected an array or map
+
+        "###);
+    }
+
     #[tokio::test]
     async fn too_many_git_specs() {
         let input = indoc! {r#"
@@ -264,7 +287,7 @@ mod test {
           |
         8 | tqdm = { git = "https://github.com/tqdm/tqdm", ref = "baaaaaab" }
           |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-        data did not match any variant of untagged enum SourcesWire
+        data did not match any variant of untagged enum Source
 
         "###);
     }
@@ -288,7 +311,7 @@ mod test {
           |
         8 | tqdm = { path = "tqdm", index = "torch" }
           |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-        data did not match any variant of untagged enum SourcesWire
+        data did not match any variant of untagged enum Source
 
         "###);
     }
@@ -348,7 +371,7 @@ mod test {
           |
         8 | tqdm = { url = "§invalid#+#*Ä" }
           |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-        data did not match any variant of untagged enum SourcesWire
+        data did not match any variant of untagged enum Source
 
         "###);
     }

crates/uv-workspace/Cargo.toml

@@ -32,6 +32,7 @@ rustc-hash = { workspace = true }
 same-file = { workspace = true }
 schemars = { workspace = true, optional = true }
 serde = { workspace = true, features = ["derive"] }
+serde-untagged = { workspace = true }
 thiserror = { workspace = true }
 tokio = { workspace = true }
 toml =  { workspace = true }

crates/uv-workspace/src/pyproject.rs

@@ -444,15 +444,26 @@ impl IntoIterator for Sources {
     }
 }
 
-#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]
-#[serde(rename_all = "kebab-case", untagged)]
-#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema), schemars(untagged))]
 #[allow(clippy::large_enum_variant)]
 enum SourcesWire {
     One(Source),
     Many(Vec<Source>),
 }
 
+impl<'de> serde::de::Deserialize<'de> for SourcesWire {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::de::Deserializer<'de>,
+    {
+        serde_untagged::UntaggedEnumVisitor::new()
+            .map(|map| map.deserialize().map(SourcesWire::One))
+            .seq(|seq| seq.deserialize().map(SourcesWire::Many))
+            .deserialize(deserializer)
+    }
+}
+
 impl TryFrom<SourcesWire> for Sources {
     type Error = SourceError;