From 43309391b30a7312afb90a79f24e11df068f5339 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ole=20Kr=C3=BCger?= <ole.kruger@trili.tech>
Date: Mon, 23 Jan 2023 15:25:41 +0000
Subject: [PATCH] Support goto-declaration LSP command

---
 helix-lsp/src/client.rs          | 25 +++++++++++++++++++++++++
 helix-term/src/commands.rs       |  1 +
 helix-term/src/commands/lsp.rs   | 25 +++++++++++++++++++++++++
 helix-term/src/keymap/default.rs |  1 +
 4 files changed, 52 insertions(+)

diff --git a/helix-lsp/src/client.rs b/helix-lsp/src/client.rs
index dd2581c6d916..6827f568d986 100644
--- a/helix-lsp/src/client.rs
+++ b/helix-lsp/src/client.rs
@@ -886,6 +886,31 @@ impl Client {
         ))
     }
 
+    pub fn goto_declaration(
+        &self,
+        text_document: lsp::TextDocumentIdentifier,
+        position: lsp::Position,
+        work_done_token: Option<lsp::ProgressToken>,
+    ) -> Option<impl Future<Output = Result<Value>>> {
+        let capabilities = self.capabilities.get().unwrap();
+
+        // Return early if the server does not support goto-declaration.
+        match capabilities.declaration_provider {
+            Some(
+                lsp::DeclarationCapability::Simple(true)
+                | lsp::DeclarationCapability::RegistrationOptions(_)
+                | lsp::DeclarationCapability::Options(_),
+            ) => (),
+            _ => return None,
+        }
+
+        Some(self.goto_request::<lsp::request::GotoDeclaration>(
+            text_document,
+            position,
+            work_done_token,
+        ))
+    }
+
     pub fn goto_type_definition(
         &self,
         text_document: lsp::TextDocumentIdentifier,
diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index e773a2c789d8..197027f9888a 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -285,6 +285,7 @@ impl MappableCommand {
         select_mode, "Enter selection extend mode",
         exit_select_mode, "Exit selection mode",
         goto_definition, "Goto definition",
+        goto_declaration, "Goto declaration",
         add_newline_above, "Add newline above",
         add_newline_below, "Add newline below",
         goto_type_definition, "Goto type definition",
diff --git a/helix-term/src/commands/lsp.rs b/helix-term/src/commands/lsp.rs
index 578eb6084196..d12aa436dd98 100644
--- a/helix-term/src/commands/lsp.rs
+++ b/helix-term/src/commands/lsp.rs
@@ -914,6 +914,31 @@ fn to_locations(definitions: Option<lsp::GotoDefinitionResponse>) -> Vec<lsp::Lo
     }
 }
 
+pub fn goto_declaration(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let language_server = language_server!(cx.editor, doc);
+    let offset_encoding = language_server.offset_encoding();
+
+    let pos = doc.position(view.id, offset_encoding);
+
+    let future = match language_server.goto_declaration(doc.identifier(), pos, None) {
+        Some(future) => future,
+        None => {
+            cx.editor
+                .set_error("Language server does not support goto-declaration");
+            return;
+        }
+    };
+
+    cx.callback(
+        future,
+        move |editor, compositor, response: Option<lsp::GotoDefinitionResponse>| {
+            let items = to_locations(response);
+            goto_impl(editor, compositor, items, offset_encoding);
+        },
+    );
+}
+
 pub fn goto_definition(cx: &mut Context) {
     let (view, doc) = current!(cx.editor);
     let language_server = language_server!(cx.editor, doc);
diff --git a/helix-term/src/keymap/default.rs b/helix-term/src/keymap/default.rs
index ef93dee08a77..d48e6935ea9b 100644
--- a/helix-term/src/keymap/default.rs
+++ b/helix-term/src/keymap/default.rs
@@ -44,6 +44,7 @@ pub fn default() -> HashMap<Mode, Keymap> {
             "l" => goto_line_end,
             "s" => goto_first_nonwhitespace,
             "d" => goto_definition,
+            "D" => goto_declaration,
             "y" => goto_type_definition,
             "r" => goto_reference,
             "i" => goto_implementation,