From 76eecd3ad78a6f91faad5a9cb846b8fcdbcb9320 Mon Sep 17 00:00:00 2001
From: JoongHyuk Shin <sjh910805@gmail.com>
Date: Sun, 19 Apr 2026 16:16:35 +0900
Subject: [PATCH] server : add missing return after validation errors in
 /infill endpoint

The /infill endpoint calls res->error() for missing input_prefix,
input_suffix, and non-string prompt, but does not return afterward.
Execution falls through to data.at() which throws out_of_range,
resulting in HTTP 500 instead of the intended HTTP 400.

Add return res; after each of the three validation error calls,
matching the pattern already used by the input_extra check below.
---
 tools/server/server-context.cpp        |  3 +++
 tools/server/tests/unit/test_infill.py | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/tools/server/server-context.cpp b/tools/server/server-context.cpp
index 70ebcc225e3..17a7a1a0a32 100644
--- a/tools/server/server-context.cpp
+++ b/tools/server/server-context.cpp
@@ -3710,14 +3710,17 @@ void server_routes::init_routes() {
         if (data.contains("prompt") && !data.at("prompt").is_string()) {
             // prompt is optional
             res->error(format_error_response("\"prompt\" must be a string", ERROR_TYPE_INVALID_REQUEST));
+            return res;
         }
 
         if (!data.contains("input_prefix")) {
             res->error(format_error_response("\"input_prefix\" is required", ERROR_TYPE_INVALID_REQUEST));
+            return res;
         }
 
         if (!data.contains("input_suffix")) {
             res->error(format_error_response("\"input_suffix\" is required", ERROR_TYPE_INVALID_REQUEST));
+            return res;
         }
 
         if (data.contains("input_extra") && !data.at("input_extra").is_array()) {
diff --git a/tools/server/tests/unit/test_infill.py b/tools/server/tests/unit/test_infill.py
index cd1a391b4ad..d17f19ad2b0 100644
--- a/tools/server/tests/unit/test_infill.py
+++ b/tools/server/tests/unit/test_infill.py
@@ -57,6 +57,19 @@ def test_invalid_input_extra_req(input_extra):
     assert "error" in res.body
 
 
+@pytest.mark.parametrize("data,expected_msg", [
+    ({"input_suffix": "}\n"}, "input_prefix"),
+    ({"input_prefix": "#include <cstdio>\n"}, "input_suffix"),
+    ({"prompt": 123, "input_prefix": "a", "input_suffix": "b"}, "prompt"),
+])
+def test_infill_missing_required_field(data, expected_msg):
+    global server
+    server.start()
+    res = server.make_request("POST", "/infill", data=data)
+    assert res.status_code == 400
+    assert expected_msg in res.body["error"]["message"]
+
+
 @pytest.mark.skipif(not is_slow_test_allowed(), reason="skipping slow test")
 def test_with_qwen_model():
     global server