fix: compute prepare_provider for RenameOptions

pygls/capabilities.py

@@ -248,9 +248,25 @@ def _with_document_on_type_formatting(self):
         return self
 
     def _with_rename(self):
-        value = self._provider_options(types.TEXT_DOCUMENT_RENAME, default=True)
-        if value is not None:
-            self.server_cap.rename_provider = value
+        server_supports_rename = types.TEXT_DOCUMENT_RENAME in self.features
+        if server_supports_rename is False:
+            return self
+
+        client_prepare_support = get_capability(
+            self.client_capabilities, "text_document.rename.prepare_support", False
+        )
+
+        # From the spec:
+        # > RenameOptions may only be specified if the client states that it supports
+        # > prepareSupport in its initial initialize request.
+        if not client_prepare_support:
+            self.server_cap.rename_provider = server_supports_rename
+
+        else:
+            self.server_cap.rename_provider = types.RenameOptions(
+                prepare_provider=types.TEXT_DOCUMENT_PREPARE_RENAME in self.features
+            )
+
         return self
 
     def _with_folding_range(self):

tests/test_feature_manager.py

@@ -709,6 +709,60 @@ def _():
     assert expected == actual
 
 
+def test_register_prepare_rename_no_client_support(feature_manager: FeatureManager):
+
+    @feature_manager.feature(lsp.TEXT_DOCUMENT_RENAME)
+    def _():
+        pass
+
+    @feature_manager.feature(lsp.TEXT_DOCUMENT_PREPARE_RENAME)
+    def _():
+        pass
+
+    expected = server_capabilities(rename_provider=True)
+
+    actual = ServerCapabilitiesBuilder(
+        lsp.ClientCapabilities(),
+        feature_manager.features.keys(),
+        feature_manager.feature_options,
+        [],
+        None,
+        None,
+    ).build()
+
+    assert expected == actual
+
+
+def test_register_prepare_rename_with_client_support(feature_manager: FeatureManager):
+
+    @feature_manager.feature(lsp.TEXT_DOCUMENT_RENAME)
+    def _():
+        pass
+
+    @feature_manager.feature(lsp.TEXT_DOCUMENT_PREPARE_RENAME)
+    def _():
+        pass
+
+    expected = server_capabilities(
+        rename_provider=lsp.RenameOptions(prepare_provider=True)
+    )
+
+    actual = ServerCapabilitiesBuilder(
+        lsp.ClientCapabilities(
+            text_document=lsp.TextDocumentClientCapabilities(
+                rename=lsp.RenameClientCapabilities(prepare_support=True)
+            )
+        ),
+        feature_manager.features.keys(),
+        feature_manager.feature_options,
+        [],
+        None,
+        None,
+    ).build()
+
+    assert expected == actual
+
+
 def test_register_inlay_hint_resolve(feature_manager: FeatureManager):
     @feature_manager.feature(lsp.TEXT_DOCUMENT_INLAY_HINT)
     def _():