Ignore invalid build backend settings when not building (#14372)

Fixes #14323

crates/uv-workspace/src/pyproject.rs

@@ -24,6 +24,7 @@ use uv_fs::{PortablePathBuf, relative_to};
 use uv_git_types::GitReference;
 use uv_macros::OptionsMetadata;
 use uv_normalize::{DefaultGroups, ExtraName, GroupName, PackageName};
+use uv_options_metadata::{OptionSet, OptionsMetadata, Visit};
 use uv_pep440::{Version, VersionSpecifiers};
 use uv_pep508::MarkerTree;
 use uv_pypi_types::{
@@ -610,7 +611,7 @@ pub struct ToolUv {
     /// Note that those settings only apply when using the `uv_build` backend, other build backends
     /// (such as hatchling) have their own configuration.
     #[option_group]
-    pub build_backend: Option<BuildBackendSettings>,
+    pub build_backend: Option<BuildBackendSettingsSchema>,
 }
 
 #[derive(Default, Debug, Clone, PartialEq, Eq)]
@@ -1684,3 +1685,44 @@ pub enum DependencyType {
     /// A dependency in `dependency-groups.{0}`.
     Group(GroupName),
 }
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[cfg_attr(test, derive(Serialize))]
+pub struct BuildBackendSettingsSchema;
+
+impl<'de> Deserialize<'de> for BuildBackendSettingsSchema {
+    fn deserialize<D>(_deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        Ok(BuildBackendSettingsSchema)
+    }
+}
+
+#[cfg(feature = "schemars")]
+impl schemars::JsonSchema for BuildBackendSettingsSchema {
+    fn schema_name() -> Cow<'static, str> {
+        BuildBackendSettings::schema_name()
+    }
+
+    fn json_schema(generator: &mut schemars::SchemaGenerator) -> schemars::Schema {
+        BuildBackendSettings::json_schema(generator)
+    }
+}
+
+impl OptionsMetadata for BuildBackendSettingsSchema {
+    fn record(visit: &mut dyn Visit) {
+        BuildBackendSettings::record(visit);
+    }
+
+    fn documentation() -> Option<&'static str> {
+        BuildBackendSettings::documentation()
+    }
+
+    fn metadata() -> OptionSet
+    where
+        Self: Sized + 'static,
+    {
+        BuildBackendSettings::metadata()
+    }
+}

crates/uv/tests/it/build_backend.rs

@@ -858,3 +858,40 @@ fn symlinked_file() -> Result<()> {
 
     Ok(())
 }
+
+/// Ignore invalid build backend settings when not building.
+///
+/// They may be from another `uv_build` version that has a different schema.
+#[test]
+fn invalid_build_backend_settings_are_ignored() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! {r#"
+        [project]
+        name = "built-by-uv"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+
+        [tool.uv.build-backend]
+        # Error: `source-include` must be a list
+        source-include = "data/build-script.py"
+
+        [build-system]
+        requires = ["uv_build>=10000,<10001"]
+        build-backend = "uv_build"
+    "#})?;
+
+    // Since we are not building, this must pass without complaining about the error in
+    // `tool.uv.build-backend`.
+    uv_snapshot!(context.filters(), context.lock(), @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    ");
+
+    Ok(())
+}