Implement Go to Declaration.

README.md

@@ -456,6 +456,7 @@ jedi-language-server aims to support Jedi's capabilities and expose them through
 - [completionItem/resolve](https://microsoft.github.io/language-server-protocol/specification#completionItem_resolve)
 - [textDocument/codeAction](https://microsoft.github.io/language-server-protocol/specification#textDocument_codeAction) (refactor.inline, refactor.extract)
 - [textDocument/completion](https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_completion)
+- [textDocument/declaration](https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_declaration)
 - [textDocument/definition](https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_definition)
 - [textDocument/documentHighlight](https://microsoft.github.io/language-server-protocol/specification#textDocument_documentHighlight)
 - [textDocument/documentSymbol](https://microsoft.github.io/language-server-protocol/specifications/specification-current/#textDocument_documentSymbol)

jedi_language_server/server.py

@@ -17,6 +17,7 @@
     INITIALIZE,
     TEXT_DOCUMENT_CODE_ACTION,
     TEXT_DOCUMENT_COMPLETION,
+    TEXT_DOCUMENT_DECLARATION,
     TEXT_DOCUMENT_DEFINITION,
     TEXT_DOCUMENT_DID_CHANGE,
     TEXT_DOCUMENT_DID_CLOSE,
@@ -306,6 +307,23 @@ def signature_help(
     )
 
 
+@SERVER.feature(TEXT_DOCUMENT_DECLARATION)
+def declaration(
+    server: JediLanguageServer, params: TextDocumentPositionParams
+) -> Optional[List[Location]]:
+    """Support Goto Declaration."""
+    document = server.workspace.get_text_document(params.text_document.uri)
+    jedi_script = jedi_utils.script(server.project, document)
+    jedi_lines = jedi_utils.line_column(params.position)
+    names = jedi_script.goto(*jedi_lines)
+    definitions = [
+        definition
+        for definition in (jedi_utils.lsp_location(name) for name in names)
+        if definition is not None
+    ]
+    return definitions if definitions else None
+
+
 @SERVER.feature(TEXT_DOCUMENT_DEFINITION)
 def definition(
     server: JediLanguageServer, params: TextDocumentPositionParams

tests/lsp_test_client/session.py

@@ -152,8 +152,15 @@ def text_document_signature_help(self, signature_help_params):
         )
         return fut.result()
 
+    def text_document_declaration(self, declaration_params):
+        """Sends text document declaration request to LSP server."""
+        fut = self._send_request(
+            "textDocument/declaration", params=declaration_params
+        )
+        return fut.result()
+
     def text_document_definition(self, definition_params):
-        """Sends text document defintion request to LSP server."""
+        """Sends text document definition request to LSP server."""
         fut = self._send_request(
             "textDocument/definition", params=definition_params
         )

tests/lsp_tests/test_definition.py

@@ -36,3 +36,31 @@ def test_definition():
         ]
 
         assert_that(actual, is_(expected))
+
+
+def test_declaration():
+    """Tests declaration on an imported module.
+
+    Test Data: tests/test_data/definition/definition_test1.py
+    """
+    with session.LspSession() as ls_session:
+        ls_session.initialize()
+        uri = as_uri(DEFINITION_TEST_ROOT / "definition_test1.py")
+        actual = ls_session.text_document_declaration(
+            {
+                "textDocument": {"uri": uri},
+                "position": {"line": 5, "character": 0},
+            }
+        )
+
+        expected = [
+            {
+                "uri": uri,
+                "range": {
+                    "start": {"line": 2, "character": 26},
+                    "end": {"line": 2, "character": 37},
+                },
+            }
+        ]
+
+        assert_that(actual, is_(expected))