Fix panic in label for completion (#152)

Closes zed-industries/zed#39328

Author: maxbrunsfeld

Cargo.lock

@@ -1,7 +1,7 @@
 
 [package]
 name = "zed_java"
-version = "6.8.0"
+version = "6.8.1"
 edition = "2024"
 publish = false
 license = "Apache-2.0"

Cargo.toml

@@ -1,6 +1,6 @@
 id = "java"
 name = "Java"
-version = "6.8.0"
+version = "6.8.1"
 schema_version = 1
 authors = [
     "Valentine Briese <valentinegb@icloud.com>",

extension.toml

@@ -156,9 +156,7 @@ impl Debugger {
             DownloadedFileType::Uncompressed,
         )
         .map_err(|err| {
-            format!(
-                "Failed to download java-debug fork from {JAVA_DEBUG_PLUGIN_FORK_URL}: {err}"
-            )
+            format!("Failed to download java-debug fork from {JAVA_DEBUG_PLUGIN_FORK_URL}: {err}")
         })?;
 
         self.plugin_path = Some(jar_path.clone());
@@ -196,9 +194,7 @@ impl Debugger {
                 return Err(err.to_owned());
             }
 
-            println!(
-                "Could not fetch debugger: {err}\nFalling back to local version."
-            );
+            println!("Could not fetch debugger: {err}\nFalling back to local version.");
 
             let exists = fs::read_dir(prefix)
                 .ok()

src/debugger.rs

@@ -448,9 +448,14 @@ impl Extension for Java {
                 };
                 let braces = " {}";
                 let code = format!("{keyword}{}{braces}", completion.label);
-                let namespace = completion
-                    .detail
-                    .map(|detail| detail[..detail.len() - completion.label.len() - 1].to_string());
+                let namespace = completion.detail.and_then(|detail| {
+                    if detail.len() > completion.label.len() {
+                        let prefix_len = detail.len() - completion.label.len() - 1;
+                        Some(detail[..prefix_len].to_string())
+                    } else {
+                        None
+                    }
+                });
                 let mut spans = vec![CodeLabelSpan::code_range(
                     keyword.len()..code.len() - braces.len(),
                 )];