project: Deduplicate identical language server hover responses (#62266)

Closes https://github.com/zed-industries/zed/issues/62262

## Solution

Identical hover responses from multiple language servers should be
displayed only once.

Different hover responses should still all be preserved, since multiple
language servers may provide complementary information.


## Showcase



https://github.com/user-attachments/assets/67246d9f-ed1c-4f5a-98f5-f10548b7fc6d



---

Release Notes:

- Deduplicated identical language server hover responses

---------

Signed-off-by: Xiaobo Liu <cppcoffee@gmail.com>
Co-authored-by: zed-zippy[bot] <234243425+zed-zippy[bot]@users.noreply.github.com>

crates/project/src/lsp_store.rs

@@ -8284,7 +8284,7 @@ impl LspStore {
                 .into_iter()
                 .flatten()
                 .collect();
-                Some(hovers)
+                Some(deduplicate_hovers(hovers))
             })
         } else {
             let all_actions_task = self.request_multiple_lsp_locally(
@@ -8294,13 +8294,13 @@ impl LspStore {
                 cx,
             );
             cx.background_spawn(async move {
-                Some(
+                Some(deduplicate_hovers(
                     all_actions_task
                         .await
                         .into_iter()
                         .filter_map(|(_, hover)| remove_empty_hover_blocks(hover?))
                         .collect::<Vec<Hover>>(),
-                )
+                ))
             })
         }
     }
@@ -13985,6 +13985,19 @@ fn remove_empty_hover_blocks(mut hover: Hover) -> Option<Hover> {
     }
 }
 
+fn deduplicate_hovers(hovers: Vec<Hover>) -> Vec<Hover> {
+    let mut unique_hovers = Vec::with_capacity(hovers.len());
+    for hover in hovers {
+        if !unique_hovers
+            .iter()
+            .any(|unique: &Hover| unique.contents == hover.contents)
+        {
+            unique_hovers.push(hover);
+        }
+    }
+    unique_hovers
+}
+
 async fn populate_labels_for_completions(
     new_completions: Vec<CoreCompletion>,
     language: Option<Arc<Language>>,

crates/project/tests/integration/project_tests.rs

@@ -9416,6 +9416,7 @@ async fn test_multiple_language_server_hovers(cx: &mut gpui::TestAppContext) {
         "TailwindServer",
         "ESLintServer",
         "NoHoverCapabilitiesServer",
+        "DuplicateTypeScriptServer",
     ];
     let mut language_servers = [
         language_registry.register_fake_lsp(
@@ -9462,6 +9463,17 @@ async fn test_multiple_language_server_hovers(cx: &mut gpui::TestAppContext) {
                 ..FakeLspAdapter::default()
             },
         ),
+        language_registry.register_fake_lsp(
+            "tsx",
+            FakeLspAdapter {
+                name: language_server_names[4],
+                capabilities: lsp::ServerCapabilities {
+                    hover_provider: Some(lsp::HoverProviderCapability::Simple(true)),
+                    ..lsp::ServerCapabilities::default()
+                },
+                ..FakeLspAdapter::default()
+            },
+        ),
     ];
 
     let (buffer, _handle) = project
@@ -9504,6 +9516,21 @@ async fn test_multiple_language_server_hovers(cx: &mut gpui::TestAppContext) {
                     ),
                 );
             }
+            "DuplicateTypeScriptServer" => {
+                servers_with_hover_requests.insert(
+                    new_server_name,
+                    new_server.set_request_handler::<lsp::request::HoverRequest, _, _>(
+                        |_, _| async move {
+                            Ok(Some(lsp::Hover {
+                                contents: lsp::HoverContents::Scalar(lsp::MarkedString::String(
+                                    "TypeScriptServer hover".to_string(),
+                                )),
+                                range: None,
+                            }))
+                        },
+                    ),
+                );
+            }
             "ESLintServer" => {
                 servers_with_hover_requests.insert(
                     new_server_name,
@@ -9545,7 +9572,7 @@ async fn test_multiple_language_server_hovers(cx: &mut gpui::TestAppContext) {
             .map(|hover| hover.contents.iter().map(|block| &block.text).join("|"))
             .sorted()
             .collect::<Vec<_>>(),
-        "Should receive hover responses from all related servers with hover capabilities"
+        "Should receive unique hover responses from all related servers with hover capabilities"
     );
 }