Fix priority for .python-versions files in uv python install (#6382)

In https://github.com/astral-sh/uv/pull/6359, I accidentally made `uv
python install` prefer `.python-version` files over `.python-versions`
files -.-, kind of niche but it's a regression.

crates/uv-python/src/version_files.rs

@@ -25,7 +25,9 @@ impl PythonVersionFile {
     /// Find a Python version file in the given directory.
     pub async fn discover(
         working_directory: impl AsRef<Path>,
+        // TODO(zanieb): Create a `DiscoverySettings` struct for these options
         no_config: bool,
+        prefer_versions: bool,
     ) -> Result<Option<Self>, std::io::Error> {
         let versions_path = working_directory.as_ref().join(PYTHON_VERSIONS_FILENAME);
         let version_path = working_directory.as_ref().join(PYTHON_VERSION_FILENAME);
@@ -39,12 +41,16 @@ impl PythonVersionFile {
             return Ok(None);
         }
 
-        if let Some(result) = Self::try_from_path(version_path).await? {
-            return Ok(Some(result));
-        };
-        if let Some(result) = Self::try_from_path(versions_path).await? {
-            return Ok(Some(result));
+        let paths = if prefer_versions {
+            [versions_path, version_path]
+        } else {
+            [version_path, versions_path]
         };
+        for path in paths {
+            if let Some(result) = Self::try_from_path(path).await? {
+                return Ok(Some(result));
+            };
+        }
 
         Ok(None)
     }

crates/uv/src/commands/project/add.rs

@@ -125,7 +125,7 @@ pub(crate) async fn add(
             let python_request = if let Some(request) = python.as_deref() {
                 // (1) Explicit request from user
                 PythonRequest::parse(request)
-            } else if let Some(request) = PythonVersionFile::discover(&*CWD, false)
+            } else if let Some(request) = PythonVersionFile::discover(&*CWD, false, false)
                 .await?
                 .and_then(PythonVersionFile::into_version)
             {
@@ -156,7 +156,7 @@ pub(crate) async fn add(
         let python_request = if let Some(request) = python.as_deref() {
             // (1) Explicit request from user
             Some(PythonRequest::parse(request))
-        } else if let Some(request) = PythonVersionFile::discover(&*CWD, false)
+        } else if let Some(request) = PythonVersionFile::discover(&*CWD, false, false)
             .await?
             .and_then(PythonVersionFile::into_version)
         {

crates/uv/src/commands/project/mod.rs

@@ -177,9 +177,10 @@ impl WorkspacePython {
         let python_request = if let Some(request) = python_request {
             Some(request)
             // (2) Request from `.python-version`
-        } else if let Some(request) = PythonVersionFile::discover(workspace.install_path(), false)
-            .await?
-            .and_then(PythonVersionFile::into_version)
+        } else if let Some(request) =
+            PythonVersionFile::discover(workspace.install_path(), false, false)
+                .await?
+                .and_then(PythonVersionFile::into_version)
         {
             Some(request)
             // (3) `Requires-Python` in `pyproject.toml`

crates/uv/src/commands/project/run.rs

@@ -109,7 +109,7 @@ pub(crate) async fn run(
         let python_request = if let Some(request) = python.as_deref() {
             Some(PythonRequest::parse(request))
             // (2) Request from `.python-version`
-        } else if let Some(request) = PythonVersionFile::discover(&*CWD, false)
+        } else if let Some(request) = PythonVersionFile::discover(&*CWD, false, false)
             .await?
             .and_then(PythonVersionFile::into_version)
         {
@@ -449,7 +449,7 @@ pub(crate) async fn run(
                     Some(PythonRequest::parse(request))
                 // (2) Request from `.python-version`
                 } else {
-                    PythonVersionFile::discover(&*CWD, no_config)
+                    PythonVersionFile::discover(&*CWD, no_config, false)
                         .await?
                         .and_then(PythonVersionFile::into_version)
                 };

crates/uv/src/commands/python/find.rs

@@ -26,7 +26,7 @@ pub(crate) async fn find(
 
     // (2) Request from `.python-version`
     if request.is_none() {
-        request = PythonVersionFile::discover(&*CWD, no_config)
+        request = PythonVersionFile::discover(&*CWD, no_config, false)
             .await?
             .and_then(PythonVersionFile::into_version);
     }

crates/uv/src/commands/python/install.rs

@@ -38,7 +38,7 @@ pub(crate) async fn install(
 
     let targets = targets.into_iter().collect::<BTreeSet<_>>();
     let requests: Vec<_> = if targets.is_empty() {
-        PythonVersionFile::discover(&*CWD, no_config)
+        PythonVersionFile::discover(&*CWD, no_config, true)
             .await?
             .map(uv_python::PythonVersionFile::into_versions)
             .unwrap_or_else(|| vec![PythonRequest::Any])

crates/uv/src/commands/python/pin.rs

@@ -38,7 +38,7 @@ pub(crate) async fn pin(
         }
     };
 
-    let version_file = PythonVersionFile::discover(&*CWD, false).await;
+    let version_file = PythonVersionFile::discover(&*CWD, false, false).await;
 
     let Some(request) = request else {
         // Display the current pinned Python version

crates/uv/src/commands/venv.rs

@@ -146,7 +146,7 @@ async fn venv_impl(
     // (2) Request from `.python-version`
     if interpreter_request.is_none() {
         // TODO(zanieb): Support `--no-config` here
-        interpreter_request = PythonVersionFile::discover(&*CWD, false)
+        interpreter_request = PythonVersionFile::discover(&*CWD, false, false)
             .await
             .into_diagnostic()?
             .and_then(PythonVersionFile::into_version);