From 36d1bbfd034d1f72a3dc54e78f4dbd3c0ad7a96e Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Wed, 10 Apr 2024 00:40:07 +0800
Subject: [PATCH] nixd: redirect doc highlight error from UI into log

---
 nixd/lib/Controller/DocumentHighlight.cpp     | 10 ++-
 .../nixd/test/document-highlight-fail.md      | 66 +++++++++++++++++++
 2 files changed, 75 insertions(+), 1 deletion(-)
 create mode 100644 nixd/tools/nixd/test/document-highlight-fail.md

diff --git a/nixd/lib/Controller/DocumentHighlight.cpp b/nixd/lib/Controller/DocumentHighlight.cpp
index e143efb2a..1dd5658e3 100644
--- a/nixd/lib/Controller/DocumentHighlight.cpp
+++ b/nixd/lib/Controller/DocumentHighlight.cpp
@@ -9,6 +9,7 @@
 #include "nixd/Controller/Controller.h"
 
 #include <boost/asio/post.hpp>
+#include <cstddef>
 #include <lspserver/Protocol.h>
 #include <nixf/Sema/ParentMap.h>
 #include <nixf/Sema/VariableLookup.h>
@@ -58,7 +59,14 @@ void Controller::onDocumentHighlight(
         std::vector<DocumentHighlight> Highlights;
         if (auto Err = highlight(*Desc, *TU->parentMap(), *TU->variableLookup(),
                                  URI, Highlights)) {
-          Reply(std::move(Err));
+          // FIXME: Empty response if there are no def-use chain found.
+          // For document highlights, the specification explicitly specified LSP
+          // should do "fuzzy" things.
+
+          // Empty response on error, don't reply all errors because this method
+          // is very frequently called.
+          Reply(std::vector<DocumentHighlight>{});
+          lspserver::elog("textDocument/documentHighlight failed: {0}", Err);
           return;
         }
         Reply(std::move(Highlights));
diff --git a/nixd/tools/nixd/test/document-highlight-fail.md b/nixd/tools/nixd/test/document-highlight-fail.md
new file mode 100644
index 000000000..f8d243777
--- /dev/null
+++ b/nixd/tools/nixd/test/document-highlight-fail.md
@@ -0,0 +1,66 @@
+# RUN: nixd --lit-test < %s | FileCheck %s
+
+<-- initialize(0)
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":0,
+   "method":"initialize",
+   "params":{
+      "processId":123,
+      "rootPath":"",
+      "capabilities":{
+      },
+      "trace":"off"
+   }
+}
+```
+
+
+<-- textDocument/didOpen
+
+```json
+{
+   "jsonrpc":"2.0",
+   "method":"textDocument/didOpen",
+   "params":{
+      "textDocument":{
+         "uri":"file:///basic.nix",
+         "languageId":"nix",
+         "version":1,
+         "text":"let x = 1; y = 2; in x + y"
+      }
+   }
+}
+```
+
+<-- textDocument/documentHighlight(2)
+
+
+```json
+{
+   "jsonrpc":"2.0",
+   "id":2,
+   "method":"textDocument/documentHighlight",
+   "params":{
+      "textDocument":{
+         "uri":"file:///basic.nix"
+      },
+      "position":{
+        "line": 0,
+        "character":1
+      }
+   }
+}
+```
+
+```
+     CHECK: "id": 2,
+CHECK-NEXT: "jsonrpc": "2.0",
+CHECK-NEXT: "result": []
+```
+
+```json
+{"jsonrpc":"2.0","method":"exit"}
+```