Don't serialise empty content on ChatCompletionMessage with tool calls

api_integration_test.go

@@ -312,3 +312,114 @@ func TestChatCompletionStructuredOutputsFunctionCalling(t *testing.T) {
 		}
 	}
 }
+
+func TestChatCompletionJsonSchemaWithFunctionCallingResponse(t *testing.T) {
+	apiToken := os.Getenv("OPENAI_TOKEN")
+	if apiToken == "" {
+		t.Skip("Skipping testing against production OpenAI API. Set OPENAI_TOKEN environment variable to enable it.")
+	}
+
+	var err error
+	c := openai.NewClient(apiToken)
+	ctx := context.Background()
+
+	type MyStructuredResponse struct {
+		PascalCase string `json:"pascal_case" required:"true" description:"PascalCase"`
+		CamelCase  string `json:"camel_case" required:"true" description:"CamelCase"`
+		KebabCase  string `json:"kebab_case" required:"true" description:"KebabCase"`
+		SnakeCase  string `json:"snake_case" required:"true" description:"SnakeCase"`
+	}
+	var result MyStructuredResponse
+	schema, err := jsonschema.GenerateSchemaForType(result)
+	if err != nil {
+		t.Fatal("CreateChatCompletion (use json_schema response) GenerateSchemaForType error")
+	}
+
+	resp, err := c.CreateChatCompletion(
+		ctx,
+		openai.ChatCompletionRequest{
+			Model: openai.GPT4oMini,
+			Messages: []openai.ChatCompletionMessage{
+				{
+					Role: openai.ChatMessageRoleSystem,
+					Content: "Please enter a string, and we will convert it into the following naming conventions:" +
+						"1. PascalCase: Each word starts with an uppercase letter, with no spaces or separators." +
+						"2. CamelCase: The first word starts with a lowercase letter, " +
+						"and subsequent words start with an uppercase letter, with no spaces or separators." +
+						"3. KebabCase: All letters are lowercase, with words separated by hyphens `-`." +
+						"4. SnakeCase: All letters are lowercase, with words separated by underscores `_`.",
+				},
+				{
+					Role:    openai.ChatMessageRoleUser,
+					Content: "Hello World",
+				},
+				{
+					Role: openai.ChatMessageRoleAssistant,
+					ToolCalls: []openai.ToolCall{
+						{
+							ID:   "call_cTSjmyVCPkRh870yFvkUrql5",
+							Type: openai.ToolTypeFunction,
+							Function: openai.FunctionCall{
+								Name:      "display_cases",
+								Arguments: `{"PascalCase":"HelloWorld","CamelCase":"helloWorld","KebabCase":"hello-world","SnakeCase":"hello_world"}`,
+							},
+						},
+					},
+				},
+				{
+					Role:       openai.ChatMessageRoleTool,
+					ToolCallID: "call_cTSjmyVCPkRh870yFvkUrql5",
+					Content: "Here are the naming conventions for 'Hello World':\n" +
+						"PascalCase: HelloWorld\n" +
+						"CamelCase: helloWorld\n" +
+						"KebabCase: hello-world\n" +
+						"SnakeCase: hello_world\n",
+				},
+			},
+			ResponseFormat: &openai.ChatCompletionResponseFormat{
+				Type: openai.ChatCompletionResponseFormatTypeJSONSchema,
+				JSONSchema: &openai.ChatCompletionResponseFormatJSONSchema{
+					Name:   "cases",
+					Schema: schema,
+					Strict: true,
+				},
+			},
+			Tools: []openai.Tool{
+				{
+					Type: openai.ToolTypeFunction,
+					Function: &openai.FunctionDefinition{
+						Name:   "display_cases",
+						Strict: true,
+						Parameters: &jsonschema.Definition{
+							Type: jsonschema.Object,
+							Properties: map[string]jsonschema.Definition{
+								"PascalCase": {
+									Type: jsonschema.String,
+								},
+								"CamelCase": {
+									Type: jsonschema.String,
+								},
+								"KebabCase": {
+									Type: jsonschema.String,
+								},
+								"SnakeCase": {
+									Type: jsonschema.String,
+								},
+							},
+							Required:             []string{"PascalCase", "CamelCase", "KebabCase", "SnakeCase"},
+							AdditionalProperties: false,
+						},
+					},
+				},
+			},
+		},
+	)
+	checks.NoError(t, err, "CreateChatCompletion returned error")
+	if err == nil {
+		err = schema.Unmarshal(resp.Choices[0].Message.Content, &result)
+		checks.NoError(t, err, "CreateChatCompletion (use json_schema response) unmarshal error")
+	}
+	if result.PascalCase != "HelloWorld" {
+		t.Errorf("PascalCase: expected 'HelloWorld', got '%s'", result.PascalCase)
+	}
+}

chat.go

@@ -114,6 +114,17 @@ func (m ChatCompletionMessage) MarshalJSON() ([]byte, error) {
 			ToolCallID   string            `json:"tool_call_id,omitempty"`
 		}(m)
 		return json.Marshal(msg)
+	} else if len(m.ToolCalls) > 0 && m.Content == "" {
+		msg := struct {
+			Role         string            `json:"role"`
+			Content      string            `json:"-"`
+			MultiContent []ChatMessagePart `json:"-"`
+			Name         string            `json:"name,omitempty"`
+			FunctionCall *FunctionCall     `json:"function_call,omitempty"`
+			ToolCalls    []ToolCall        `json:"tool_calls,omitempty"`
+			ToolCallID   string            `json:"tool_call_id,omitempty"`
+		}(m)
+		return json.Marshal(msg)
 	}
 	msg := struct {
 		Role         string            `json:"role"`