lsp: Support Goto Declaration (#15785)

Adds support for [Goto
Declaration](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_declaration)
LSP command.

I am particularly interested in [this for Rust
projects](https://rust-analyzer.github.io/manual.html#go-to-declaration),
to be able to navigate to the place where a trait method is declared,
coming from a trait method implementation.

I noticed this was something I could do in VSCode before, but was
somehow missing is Zed. Thanks to the already existing infrastructure
for Goto Definition, I just followed and copy-paste-adapted it for Goto
Declaration.

As a bonus, I added `ctrl-F12` and `alt-ctrl-F12` as default macOS
keybindings for `GoToDeclaration` and `GoToDeclarationSplit`,
respectively. They are not keybindings from another editor, but I
figured they made sense to be grouped along with the other *F12
commands.

### Release Notes:

- Added "Go to declaration" editor action.
- vim: Breaking change to keybindings after introduction of the `Go to
declaration` editor action. The new keybindings are the following (and
can be found [here](https://zed.dev/docs/vim), alongside the other key
bindings):
  - `g d` - Go to definition
  - `g D` - Go to declaration
  - `g y` - Go to type definition
  - `g I` - Go to implementation




https://github.com/user-attachments/assets/ee5c10a8-94f0-4e50-afbb-6f71db540c1b

---------

Co-authored-by: Thorsten Ball <mrnugget@gmail.com>

crates/project/src/lsp_command.rs

@@ -117,6 +117,10 @@ pub struct GetDefinition {
     pub position: PointUtf16,
 }
 
+pub(crate) struct GetDeclaration {
+    pub position: PointUtf16,
+}
+
 pub(crate) struct GetTypeDefinition {
     pub position: PointUtf16,
 }
@@ -521,6 +525,106 @@ impl LspCommand for GetDefinition {
     }
 }
 
+#[async_trait(?Send)]
+impl LspCommand for GetDeclaration {
+    type Response = Vec<LocationLink>;
+    type LspRequest = lsp::request::GotoDeclaration;
+    type ProtoRequest = proto::GetDeclaration;
+
+    fn check_capabilities(&self, capabilities: AdapterServerCapabilities) -> bool {
+        capabilities
+            .server_capabilities
+            .declaration_provider
+            .is_some()
+    }
+
+    fn to_lsp(
+        &self,
+        path: &Path,
+        _: &Buffer,
+        _: &Arc<LanguageServer>,
+        _: &AppContext,
+    ) -> lsp::GotoDeclarationParams {
+        lsp::GotoDeclarationParams {
+            text_document_position_params: lsp::TextDocumentPositionParams {
+                text_document: lsp::TextDocumentIdentifier {
+                    uri: lsp::Url::from_file_path(path).unwrap(),
+                },
+                position: point_to_lsp(self.position),
+            },
+            work_done_progress_params: Default::default(),
+            partial_result_params: Default::default(),
+        }
+    }
+
+    async fn response_from_lsp(
+        self,
+        message: Option<lsp::GotoDeclarationResponse>,
+        project: Model<Project>,
+        buffer: Model<Buffer>,
+        server_id: LanguageServerId,
+        cx: AsyncAppContext,
+    ) -> Result<Vec<LocationLink>> {
+        location_links_from_lsp(message, project, buffer, server_id, cx).await
+    }
+
+    fn to_proto(&self, project_id: u64, buffer: &Buffer) -> proto::GetDeclaration {
+        proto::GetDeclaration {
+            project_id,
+            buffer_id: buffer.remote_id().into(),
+            position: Some(language::proto::serialize_anchor(
+                &buffer.anchor_before(self.position),
+            )),
+            version: serialize_version(&buffer.version()),
+        }
+    }
+
+    async fn from_proto(
+        message: proto::GetDeclaration,
+        _: Model<Project>,
+        buffer: Model<Buffer>,
+        mut cx: AsyncAppContext,
+    ) -> Result<Self> {
+        let position = message
+            .position
+            .and_then(deserialize_anchor)
+            .ok_or_else(|| anyhow!("invalid position"))?;
+        buffer
+            .update(&mut cx, |buffer, _| {
+                buffer.wait_for_version(deserialize_version(&message.version))
+            })?
+            .await?;
+        Ok(Self {
+            position: buffer.update(&mut cx, |buffer, _| position.to_point_utf16(buffer))?,
+        })
+    }
+
+    fn response_to_proto(
+        response: Vec<LocationLink>,
+        project: &mut Project,
+        peer_id: PeerId,
+        _: &clock::Global,
+        cx: &mut AppContext,
+    ) -> proto::GetDeclarationResponse {
+        let links = location_links_to_proto(response, project, peer_id, cx);
+        proto::GetDeclarationResponse { links }
+    }
+
+    async fn response_from_proto(
+        self,
+        message: proto::GetDeclarationResponse,
+        project: Model<Project>,
+        _: Model<Buffer>,
+        cx: AsyncAppContext,
+    ) -> Result<Vec<LocationLink>> {
+        location_links_from_proto(message.links, project, cx).await
+    }
+
+    fn buffer_id_from_proto(message: &proto::GetDeclaration) -> Result<BufferId> {
+        BufferId::new(message.buffer_id)
+    }
+}
+
 #[async_trait(?Send)]
 impl LspCommand for GetImplementation {
     type Response = Vec<LocationLink>;

crates/project/src/project.rs

@@ -714,6 +714,7 @@ impl Project {
         client.add_model_request_handler(Self::handle_lsp_command::<GetCompletions>);
         client.add_model_request_handler(Self::handle_lsp_command::<GetHover>);
         client.add_model_request_handler(Self::handle_lsp_command::<GetDefinition>);
+        client.add_model_request_handler(Self::handle_lsp_command::<GetDeclaration>);
         client.add_model_request_handler(Self::handle_lsp_command::<GetTypeDefinition>);
         client.add_model_request_handler(Self::handle_lsp_command::<GetDocumentHighlights>);
         client.add_model_request_handler(Self::handle_lsp_command::<GetReferences>);
@@ -5463,6 +5464,30 @@ impl Project {
         self.definition_impl(buffer, position, cx)
     }
 
+    fn declaration_impl(
+        &self,
+        buffer: &Model<Buffer>,
+        position: PointUtf16,
+        cx: &mut ModelContext<Self>,
+    ) -> Task<Result<Vec<LocationLink>>> {
+        self.request_lsp(
+            buffer.clone(),
+            LanguageServerToQuery::Primary,
+            GetDeclaration { position },
+            cx,
+        )
+    }
+
+    pub fn declaration<T: ToPointUtf16>(
+        &self,
+        buffer: &Model<Buffer>,
+        position: T,
+        cx: &mut ModelContext<Self>,
+    ) -> Task<Result<Vec<LocationLink>>> {
+        let position = position.to_point_utf16(buffer.read(cx));
+        self.declaration_impl(buffer, position, cx)
+    }
+
     fn type_definition_impl(
         &self,
         buffer: &Model<Buffer>,