Avoid adding extra newline for script with non-empty prelude (#6366)

Closes #6364

crates/uv-scripts/src/lib.rs

@@ -80,11 +80,15 @@ impl Pep723Script {
         let metadata = Pep723Metadata::from_str(&default_metadata)?;
 
         //  Extract the shebang and script content.
-        let (prelude, postlude) = extract_shebang(&contents)?;
+        let (shebang, postlude) = extract_shebang(&contents)?;
 
         Ok(Self {
             path: file.as_ref().to_path_buf(),
-            prelude,
+            prelude: if shebang.is_empty() {
+                String::new()
+            } else {
+                format!("{shebang}\n")
+            },
             metadata,
             postlude,
         })
@@ -94,11 +98,7 @@ impl Pep723Script {
     pub async fn write(&self, metadata: &str) -> Result<(), Pep723Error> {
         let content = format!(
             "{}{}{}",
-            if self.prelude.is_empty() {
-                String::new()
-            } else {
-                format!("{}\n", self.prelude)
-            },
+            self.prelude,
             serialize_metadata(metadata),
             self.postlude
         );

crates/uv/tests/edit.rs

@@ -3584,6 +3584,62 @@ fn add_script_without_metadata_table_with_shebang() -> Result<()> {
     Ok(())
 }
 
+/// Add to a script with a metadata table and a shebang.
+#[test]
+fn add_script_with_metadata_table_and_shebang() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let script = context.temp_dir.child("script.py");
+    script.write_str(indoc! {r#"
+        #!/usr/bin/env python3
+        # /// script
+        # requires-python = ">=3.12"
+        # dependencies = []
+        # ///
+        import requests
+        from rich.pretty import pprint
+
+        resp = requests.get("https://peps.python.org/api/peps.json")
+        data = resp.json()
+        pprint([(k, v["title"]) for k, v in data.items()][:10])
+    "#})?;
+
+    uv_snapshot!(context.filters(), context.add(&["rich", "requests<3"]).arg("--script").arg("script.py"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Updated `script.py`
+    "###);
+
+    let script_content = fs_err::read_to_string(context.temp_dir.join("script.py"))?;
+
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        assert_snapshot!(
+            script_content, @r###"
+        #!/usr/bin/env python3
+        # /// script
+        # requires-python = ">=3.12"
+        # dependencies = [
+        #     "rich",
+        #     "requests<3",
+        # ]
+        # ///
+        import requests
+        from rich.pretty import pprint
+
+        resp = requests.get("https://peps.python.org/api/peps.json")
+        data = resp.json()
+        pprint([(k, v["title"]) for k, v in data.items()][:10])
+        "###
+        );
+    });
+    Ok(())
+}
+
 /// Add to a script without a metadata table, but with a docstring.
 #[test]
 fn add_script_without_metadata_table_with_docstring() -> Result<()> {