SetContentID doesn't actually set content ID for attachments

[kevinmu]

Issue Summary

I'm trying to send an email with an attachment, and I am trying to set the content ID for that attachment. However, when I select 'view original' in GMail, it appears that the attachment does not have a content ID set. However, the other fields (content-disposition, filename, etc.) seem to be set correctly.

Steps to Reproduce

func sendEmail() error {
	email := mail.NewV3Mail()
	email.SetFrom(mail.NewEmail("from@from.com", "to@to.com"))
	email.Subject = "Test Email"
	per := mail.NewPersonalization()
	per.AddTos(mail.NewEmail(to.Name, to.Address))
	email.AddPersonalizations(per)

	// Set content
	content := mail.NewContent("text/html", "This is a test.")
	email.AddContent(content)

	// Attach .png file
	pngAttachment := mail.NewAttachment()
	dat, err = ioutil.ReadFile("MY_FILE.png")
	if err != nil {
		fmt.Println(err)
	}
	encoded = base64.StdEncoding.EncodeToString([]byte(dat))
	pngAttachment.SetContent(encoded)
	pngAttachment.SetType("image/png")
	pngAttachment.SetFilename("a1.png")
	pngAttachment.SetDisposition("attachment")

        // this doesn't end up being set :(
	pngAttachment.SetContentID("a1")

	email.AddAttachment(pngAttachment)
	// Send the email
	request := sendgrid.GetRequest(
		"<API_KEY>",
		"/v3/mail/send",
		"https://api.sendgrid.com",
	)
	request.Method = "POST"
	request.Body = mail.GetRequestBody(email)
	response, err := sendgrid.API(request)
	if err != nil {
		println(err)
	} else {
		fmt.Println(response.StatusCode)
		fmt.Println(response.Body)
		fmt.Println(response.Headers)
	}
	return nil
}

Technical details:

• sendgrid-go Version: 8caf17a (v3.4.1)

• Go Version: 1.9.2

[thinkingserious]

Hi @kevinmu,

Could you please provide the output of request.Body?

Thanks!

With Best Regards,

Elmer

[kevinmu]

Hey, sorry for the delay. This issue is fixed if you use .SetDisposition("inline") instead of .SetDisposition("attachment"); it was pretty difficult for me to find this, though. I believe I did it through a lot of Googling, as opposed to through any official documentation.

[thinkingserious]

Awesome, thanks for circling back! I'll leave this open so we can update the documentation for clarity.

[anchepiece]

Hello @thinkingserious 👋,

Thanks to the sendgrid team for open sourcing this and other projects.

I noticed that there is no mention of the issue on the official v3 docs: https://sendgrid.com/docs/API_Reference/Web_API_v3/Mail/index.html
It would be nice to confirm that this is really the case for all projects consuming the API in this way.

If there is a need to update ContentID usage here, there are a few places where a notice could help:

• As a comment in the helper example itself
• In the mail readme https://github.com/sendgrid/sendgrid-go/blob/master/helpers/mail/README.md
• In the use cases document https://github.com/sendgrid/sendgrid-go/blob/master/USE_CASES.md#attachments

Would it also be appropriate to remove SetContentID from any examples when using content disposition "attachment"?

[thinkingserious]

Those are all solid recommendations @anchepiece. I will reserve this PR for you :)

[anchepiece]

Thanks @thinkingserious.

Any suggestions or corrections?

[thinkingserious]

I think you are headed in the right direction. Please submit a PR and I'll review it. Thanks!