feat: Support Structured Outputs (#813)

* feat: Support Structured Outputs

* feat: Support Structured Outputs

* update imports

* add integration test

* update JSON schema comments

api_integration_test.go

@@ -4,6 +4,7 @@ package openai_test
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"io"
 	"os"
@@ -178,3 +179,63 @@ func TestAPIError(t *testing.T) {
 		t.Fatal("Empty error message occurred")
 	}
 }
+
+func TestChatCompletionResponseFormat_JSONSchema(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()
+
+	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",
+				},
+			},
+			ResponseFormat: &openai.ChatCompletionResponseFormat{
+				Type: openai.ChatCompletionResponseFormatTypeJSONSchema,
+				JSONSchema: openai.ChatCompletionResponseFormatJSONSchema{
+					Name: "cases",
+					Schema: jsonschema.Definition{
+						Type: jsonschema.Object,
+						Properties: map[string]jsonschema.Definition{
+							"PascalCase": jsonschema.Definition{Type: jsonschema.String},
+							"CamelCase":  jsonschema.Definition{Type: jsonschema.String},
+							"KebabCase":  jsonschema.Definition{Type: jsonschema.String},
+							"SnakeCase":  jsonschema.Definition{Type: jsonschema.String},
+						},
+						Required:             []string{"PascalCase", "CamelCase", "KebabCase", "SnakeCase"},
+						AdditionalProperties: false,
+					},
+					Strict: true,
+				},
+			},
+		},
+	)
+	checks.NoError(t, err, "CreateChatCompletion (use json_schema response) returned error")
+	var result = make(map[string]string)
+	err = json.Unmarshal([]byte(resp.Choices[0].Message.Content), &result)
+	checks.NoError(t, err, "CreateChatCompletion (use json_schema response) unmarshal error")
+	for _, key := range []string{"PascalCase", "CamelCase", "KebabCase", "SnakeCase"} {
+		if _, ok := result[key]; !ok {
+			t.Errorf("key:%s does not exist.", key)
+		}
+	}
+}