From 25ced2e3c2e1c5aa81c8b51fec721613563687a6 Mon Sep 17 00:00:00 2001
From: Antonio Scandurra <me@as-cii.com>
Date: Fri, 9 May 2025 14:14:36 +0200
Subject: [PATCH] Fix error when Copilot calls tools without arguments (#30371)

Fixes https://github.com/zed-industries/zed/issues/30346

The model can output an empty string to indicate the absence of
arguments, which can't be parsed as a `serde_json::Value`. When that
happens, we now create an empty object instead on behalf of the model.

Release Notes:

- Fixed a bug that prevented Copilot models from calling the
`diagnostic` tool.
---
 .../src/provider/copilot_chat.rs              | 47 +++++++++++--------
 1 file changed, 28 insertions(+), 19 deletions(-)

diff --git a/crates/language_models/src/provider/copilot_chat.rs b/crates/language_models/src/provider/copilot_chat.rs
index fe11458282..d200248269 100644
--- a/crates/language_models/src/provider/copilot_chat.rs
+++ b/crates/language_models/src/provider/copilot_chat.rs
@@ -368,25 +368,34 @@ pub fn map_to_language_model_completion_events(
                             }
                             Some("tool_calls") => {
                                 events.extend(state.tool_calls_by_index.drain().map(
-                                    |(_, tool_call)| match serde_json::Value::from_str(
-                                        &tool_call.arguments,
-                                    ) {
-                                        Ok(input) => Ok(LanguageModelCompletionEvent::ToolUse(
-                                            LanguageModelToolUse {
-                                                id: tool_call.id.clone().into(),
-                                                name: tool_call.name.as_str().into(),
-                                                is_input_complete: true,
-                                                input,
-                                                raw_input: tool_call.arguments.clone(),
-                                            },
-                                        )),
-                                        Err(error) => {
-                                            Err(LanguageModelCompletionError::BadInputJson {
-                                                id: tool_call.id.into(),
-                                                tool_name: tool_call.name.as_str().into(),
-                                                raw_input: tool_call.arguments.into(),
-                                                json_parse_error: error.to_string(),
-                                            })
+                                    |(_, tool_call)| {
+                                        // The model can output an empty string
+                                        // to indicate the absence of arguments.
+                                        // When that happens, create an empty
+                                        // object instead.
+                                        let arguments = if tool_call.arguments.is_empty() {
+                                            Ok(serde_json::Value::Object(Default::default()))
+                                        } else {
+                                            serde_json::Value::from_str(&tool_call.arguments)
+                                        };
+                                        match arguments {
+                                            Ok(input) => Ok(LanguageModelCompletionEvent::ToolUse(
+                                                LanguageModelToolUse {
+                                                    id: tool_call.id.clone().into(),
+                                                    name: tool_call.name.as_str().into(),
+                                                    is_input_complete: true,
+                                                    input,
+                                                    raw_input: tool_call.arguments.clone(),
+                                                },
+                                            )),
+                                            Err(error) => {
+                                                Err(LanguageModelCompletionError::BadInputJson {
+                                                    id: tool_call.id.into(),
+                                                    tool_name: tool_call.name.as_str().into(),
+                                                    raw_input: tool_call.arguments.into(),
+                                                    json_parse_error: error.to_string(),
+                                                })
+                                            }
                                         }
                                     },
                                 ));