Treat .pyw files as scripts in uv run on Windows (#6453)

Closes https://github.com/astral-sh/uv/issues/6435

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

@@ -722,6 +722,8 @@ enum RunCommand {
     Python(Vec<OsString>),
     /// Execute a `python` script.
     PythonScript(PathBuf, Vec<OsString>),
+    /// Execute a `pythonw` script (Windows only).
+    PythonGuiScript(PathBuf, Vec<OsString>),
     /// Execute an external command.
     External(OsString, Vec<OsString>),
     /// Execute an empty command (in practice, `python` with no arguments).
@@ -734,6 +736,7 @@ impl RunCommand {
         match self {
             Self::Python(_) => Cow::Borrowed("python"),
             Self::PythonScript(_, _) | Self::Empty => Cow::Borrowed("python"),
+            Self::PythonGuiScript(_, _) => Cow::Borrowed("pythonw"),
             Self::External(executable, _) => executable.to_string_lossy(),
         }
     }
@@ -752,6 +755,25 @@ impl RunCommand {
                 process.args(args);
                 process
             }
+            Self::PythonGuiScript(target, args) => {
+                let python_executable = interpreter.sys_executable();
+
+                // Use `pythonw.exe` if it exists, otherwise fall back to `python.exe`.
+                // See `install-wheel-rs::get_script_executable`.gd
+                let pythonw_executable = python_executable
+                    .file_name()
+                    .map(|name| {
+                        let new_name = name.to_string_lossy().replace("python", "pythonw");
+                        python_executable.with_file_name(new_name)
+                    })
+                    .filter(|path| path.is_file())
+                    .unwrap_or_else(|| python_executable.to_path_buf());
+
+                let mut process = Command::new(&pythonw_executable);
+                process.arg(target);
+                process.args(args);
+                process
+            }
             Self::External(executable, args) => {
                 let mut process = Command::new(executable);
                 process.args(args);
@@ -779,6 +801,13 @@ impl std::fmt::Display for RunCommand {
                 }
                 Ok(())
             }
+            Self::PythonGuiScript(target, args) => {
+                write!(f, "pythonw {}", target.display())?;
+                for arg in args {
+                    write!(f, " {}", arg.to_string_lossy())?;
+                }
+                Ok(())
+            }
             Self::External(executable, args) => {
                 write!(f, "{}", executable.to_string_lossy())?;
                 for arg in args {
@@ -811,6 +840,13 @@ impl From<&ExternalCommand> for RunCommand {
             && target_path.exists()
         {
             Self::PythonScript(target_path, args.to_vec())
+        } else if cfg!(windows)
+            && target_path
+                .extension()
+                .is_some_and(|ext| ext.eq_ignore_ascii_case("pyw"))
+            && target_path.exists()
+        {
+            Self::PythonGuiScript(target_path, args.to_vec())
         } else {
             Self::External(
                 target.clone(),

crates/uv/tests/run.rs

@@ -356,6 +356,46 @@ fn run_pep723_script() -> Result<()> {
     Ok(())
 }
 
+/// Run a `.pyw` script. The script should be executed with `pythonw.exe`.
+#[test]
+#[cfg(windows)]
+fn run_pythonw_script() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(indoc! { r#"
+        [project]
+        name = "foo"
+        version = "1.0.0"
+        requires-python = ">=3.8"
+        dependencies = ["anyio"]
+        "#
+    })?;
+
+    let test_script = context.temp_dir.child("main.pyw");
+    test_script.write_str(indoc! { r"
+        import anyio
+       "
+    })?;
+
+    uv_snapshot!(context.filters(), context.run().arg("--preview").arg("main.pyw"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 6 packages in [TIME]
+    Prepared 4 packages in [TIME]
+    Installed 4 packages in [TIME]
+     + anyio==4.3.0
+     + foo==1.0.0 (from file://[TEMP_DIR]/)
+     + idna==3.6
+     + sniffio==1.3.1
+    "###);
+
+    Ok(())
+}
+
 /// Run a PEP 723-compatible script with `tool.uv` metadata.
 #[test]
 fn run_pep723_script_metadata() -> Result<()> {