feat: Add MIMEType field to ChatMessageImageURL

[kangkangkk]

1. Added MIMEType field to ChatMessageImageURL struct

2. allowing users to specify the MIME type of image URLs in multi-content messages.

3. relevant API doc
   https://platform.openai.com/docs/api-reference/uploads/create

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.61%. Comparing base (5d7a276) to head (609949d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1095      +/-   ##
==========================================
+ Coverage   99.59%   99.61%   +0.02%     
==========================================
  Files          34       34              
  Lines        2209     1841     -368     
==========================================
- Hits         2200     1834     -366     
+ Misses          6        4       -2     
  Partials        3        3              

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[Copilot]

Pull request overview

This PR adds support for specifying MIME types in image URLs for multi-content chat messages by introducing a new MIMEType field to the ChatMessageImageURL struct.

Changes:

• Added MIMEType field to ChatMessageImageURL struct with proper JSON tag mime_type
• Added test case to verify the new field can be used in chat completion requests

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
chat.go	Added MIMEType string field to ChatMessageImageURL struct with json:"mime_type,omitempty" tag
chat_test.go	Added TestChatMessageImageURLMIMEType test function to verify usage of the new MIMEType field

Comments suppressed due to low confidence (1)

chat_test.go:908

• The TestMultipartChatMessageSerialization test should be updated to include test cases for the new MIMEType field. Consider adding a test case that verifies JSON serialization and deserialization of ChatMessageImageURL with the MIMEType field set to ensure backward compatibility and proper JSON marshaling with the "mime_type" tag.

func TestMultipartChatMessageSerialization(t *testing.T) {
	jsonText := `[{"role":"system","content":"system-message"},` +
		`{"role":"user","content":[{"type":"text","text":"nice-text"},` +
		`{"type":"image_url","image_url":{"url":"URL","detail":"high"}}]}]`

	var msgs []openai.ChatCompletionMessage
	err := json.Unmarshal([]byte(jsonText), &msgs)
	if err != nil {
		t.Fatalf("Expected no error: %s", err)
	}
	if len(msgs) != 2 {
		t.Errorf("unexpected number of messages")
	}
	if msgs[0].Role != "system" || msgs[0].Content != "system-message" || msgs[0].MultiContent != nil {
		t.Errorf("invalid user message: %v", msgs[0])
	}
	if msgs[1].Role != "user" || msgs[1].Content != "" || len(msgs[1].MultiContent) != 2 {
		t.Errorf("invalid user message")
	}
	parts := msgs[1].MultiContent
	if parts[0].Type != "text" || parts[0].Text != "nice-text" {
		t.Errorf("invalid text part: %v", parts[0])
	}
	if parts[1].Type != "image_url" || parts[1].ImageURL.URL != "URL" || parts[1].ImageURL.Detail != "high" {
		t.Errorf("invalid image_url part")
	}

	s, err := json.Marshal(msgs)
	if err != nil {
		t.Fatalf("Expected no error: %s", err)
	}
	res := strings.ReplaceAll(string(s), " ", "")
	if res != jsonText {
		t.Fatalf("invalid message: %s", string(s))
	}

	invalidMsg := []openai.ChatCompletionMessage{
		{
			Role:    "user",
			Content: "some-text",
			MultiContent: []openai.ChatMessagePart{
				{
					Type: "text",
					Text: "nice-text",
				},
			},
		},
	}
	_, err = json.Marshal(invalidMsg)
	if !errors.Is(err, openai.ErrContentFieldsMisused) {
		t.Fatalf("Expected error: %s", err)
	}

	err = json.Unmarshal([]byte(`["not-a-message"]`), &msgs)
	if err == nil {
		t.Fatalf("Expected error")
	}

	emptyMultiContentMsg := openai.ChatCompletionMessage{
		Role:         "user",
		MultiContent: []openai.ChatMessagePart{},
	}
	s, err = json.Marshal(emptyMultiContentMsg)
	if err != nil {
		t.Fatalf("Unexpected error")
	}
	res = strings.ReplaceAll(string(s), " ", "")
	if res != `{"role":"user"}` {
		t.Fatalf("invalid message: %s", string(s))
	}
}

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