Do not re-resolve with a new Python version in uv tool if it is incompatible with --python

Author: zanieb

crates/uv/src/commands/tool/common.rs

@@ -98,14 +98,6 @@ pub(crate) async fn refine_interpreter(
         return Ok(None);
     }
 
-    // If the user passed a `--python` request, and the refined interpreter is incompatible, we
-    // can't use it.
-    if let Some(python_request) = python_request {
-        if !python_request.satisfied(interpreter, cache) {
-            return Ok(None);
-        }
-    }
-
     // We want an interpreter that's as close to the required version as possible. If we choose the
     // "latest" Python, we risk choosing a version that lacks wheels for the tool's requirements
     // (assuming those requirements don't publish source distributions).
@@ -135,15 +127,15 @@ pub(crate) async fn refine_interpreter(
         Bound::Unbounded => unreachable!("`requires-python` should never be unbounded"),
     };
 
-    let python_request = PythonRequest::Version(VersionRequest::Range(
+    let requires_python_request = PythonRequest::Version(VersionRequest::Range(
         VersionSpecifiers::from_iter([lower_bound, upper_bound]),
         PythonVariant::default(),
     ));
 
-    debug!("Refining interpreter with: {python_request}");
+    debug!("Refining interpreter with: {requires_python_request}");
 
     let interpreter = PythonInstallation::find_or_download(
-        Some(&python_request),
+        Some(&requires_python_request),
         EnvironmentPreference::OnlySystem,
         python_preference,
         python_downloads,
@@ -158,6 +150,14 @@ pub(crate) async fn refine_interpreter(
     .await?
     .into_interpreter();
 
+    // If the user passed a `--python` request, and the refined interpreter is incompatible, we
+    // can't use it.
+    if let Some(python_request) = python_request {
+        if !python_request.satisfied(&interpreter, cache) {
+            return Ok(None);
+        }
+    }
+
     Ok(Some(interpreter))
 }
 

crates/uv/tests/it/tool_run.rs

@@ -3026,6 +3026,7 @@ fn tool_run_reresolve_python() -> anyhow::Result<()> {
      + foo==1.0.0 (from file://[TEMP_DIR]/foo)
     ");
 
+    // When an incompatible Python version is explicitly requested, we should not re-resolve
     uv_snapshot!(context.filters(), context.tool_run()
         .arg("--from")
         .arg("./foo")
@@ -3034,6 +3035,25 @@ fn tool_run_reresolve_python() -> anyhow::Result<()> {
         .arg("foo")
         .env(EnvVars::UV_TOOL_DIR, tool_dir.as_os_str())
         .env(EnvVars::XDG_BIN_HOME, bin_dir.as_os_str()), @r"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+      × No solution found when resolving tool dependencies:
+      ╰─▶ Because the current Python version (3.11.[X]) does not satisfy Python>=3.12 and foo==1.0.0 depends on Python>=3.12, we can conclude that foo==1.0.0 cannot be used.
+          And because only foo==1.0.0 is available and you require foo, we can conclude that your requirements are unsatisfiable.
+    ");
+
+    // Unless the discovered interpreter is compatible with the request
+    uv_snapshot!(context.filters(), context.tool_run()
+        .arg("--from")
+        .arg("./foo")
+        .arg("--python")
+        .arg(">=3.11")
+        .arg("foo")
+        .env(EnvVars::UV_TOOL_DIR, tool_dir.as_os_str())
+        .env(EnvVars::XDG_BIN_HOME, bin_dir.as_os_str()), @r"
     success: true
     exit_code: 0
     ----- stdout -----