Cannot send messages with .txt or .pdf attachments when body is text+html: `gm_send_message()` and `gm_send_draft()` are dropping some MIME parts

[FrancoisR95]

Summary of the bug
When trying to send messages with text+html body and .txt or .pdf attachments, gm_send_message() and gm_send_draft() are dropping some MIME parts from the message:

• in case there is a .txt attachment, the text of the message is dropped when sending ("text/plain" & "text/html" MIME parts are missing)
• in case there is a .pdf attachment, the attachment is dropped when sending ("application/pdf" MIME part is missing)

Some other file extensions are affected too by such problem: see bug #81 which was open in 2017 but has been closed by mistake in 2019 while in fact the bug was not resolved.

This bug is observed with gmailr 2.0.0 but was apparently already present in previous versions (see bug #81).

Code for reproducing the bug

# Main email message's elements
        email_recipient = "...@..." # /!\ enter a valid test email address here /!\
        email_sender = "me"
        email_subject = "Test message without attachment"
        email_subject_txt = "Test message with txt attachment"
        email_subject_pdf = "Test message with pdf attachment"
        email_text_body = "Hello,\n\nhere attached is your file!\n\nBest regards,\n\nMe"
        email_html_body = "<div dir=ltr>Hello,<br><br>here attached is <b>your file</b>!<br><br>Best regards,<br><br>Me</div>"
# Creating a .txt file
        txt_filename <- tempfile(fileext=".txt")
        writeLines("This is a .txt file\nplease help solving this bug!\nBla bla bla,\nbla bla bla", txt_filename)
# Creating a .pdf file
        pdf_filename <- tempfile(fileext=".pdf")
        pdf(pdf_filename)
        plot(c(1:10),c(1:10)); text(1,10,"This is a basic PDF file", pos=4)
        dev.off()
        
# Creating MIME email messages
        msg_basic <- gm_mime() |> # basic without attachment
          gm_from(email_sender) |>
          gm_to(email_recipient) |>
          gm_subject(email_subject) |>
          gm_text_body(email_text_body) |>
          gm_html_body(email_html_body)
        
        msg_with_att_txt <- msg_basic |> # same with .txt attachment
          gm_subject(email_subject_txt) |>
          gm_attach_file(txt_filename)
      
        msg_with_att_pdf <- msg_basic |> # same with .pdf attachment
          gm_subject(email_subject_pdf) |>
          gm_attach_file(pdf_filename)
        
# Sending MIME email messages directly
        gm_send_message(msg_basic) # The message is correctly sent with its 2 MIME parts ("text/plain" & "text/html")
        gm_send_message(msg_with_att_txt) # /!\ BUG /!\: the message is sent but only with the .txt attachment (missing "text/plain" & "text/html" MIME parts)
        gm_send_message(msg_with_att_pdf) # /!\ BUG /!\: the message is sent but missing its attachment (missing "application/pdf" MIME part)
        
# Creating draft email messages
        draft_richId_basic <- gm_create_draft(msg_basic) # The draft is correctly created in the gmail draft folder
        draft_richId_with_att_txt <- gm_create_draft(msg_with_att_txt) # The draft is correctly created in the gmail draft folder
        draft_richId_with_att_pdf <- gm_create_draft(msg_with_att_pdf) # The draft is correctly created in the gmail draft folder
        
# Sending draft email messages
        gm_send_draft(draft_richId_basic) # The message is correctly sent with its 2 MIME parts ("text/plain" & "text/html")
        gm_send_draft(draft_richId_with_att_txt) # /!\ BUG /!\: the message is sent but only with the .txt attachment (missing "text/plain" & "text/html" MIME parts)
        gm_send_draft(draft_richId_with_att_pdf) # /!\ BUG /!\: the message is sent but missing its attachment (missing "application/pdf" MIME part)

Partial workaround
Draft messages with attachment created with gm_create_draft() can be sent manually from Gmail's web client and this works fine. The bug is only when sending them from R with gm_send_draft(), or when sending them directly with gm_send_message().

[FrancoisR95]

Cause of this bug
I investigated this bug and found that the problem is with the as.character.mime method defined in gmailr 2.0.0 for converting a "mime" email object into character:

• when manually sending an email having text+html body, plus attachment(s), from the Gmail web interface, the email is created by this interface as multipart/mixed MIME message,
• whereas the as.character.mime method from gmailr 2.0.0, called by gm_send_message() and gm_create_draft(), instead creates a multipart/alternative MIME message (which is the correct structure for text+html body messages without attachment but not for messages with attachments).

If an email is created by gm_create_draft(), it will have this wrong multipart/alternative structure instead of multipart/mixed and therefore gm_send_draft() will not send it correctly, however if it is sent manually from the Gmail web interface, this interface will correct its structure and that's why in such case the sending is successful and the source message which the recipient receives has got the needed multipart/mixed structure.

Workaround for sending from R a message with text+html body, plus attachment(s)
In this case, we want to have a multipart/mixed structure containing a text+html body with multipart/alternative structure. Therefore, here is a workaround to the code given when opening this bug:

library(stringr) # Replace String (not needed if using tidyverse as it is included in that library)

# Example with .txt attachment
# 1. Extract the "multipart/alternative" section from msg_basic (which is the email message with text+html body but no attachment)
        msg_basic_chr <- as.character(msg_basic) 
        # cat(msg_basic_chr) # the content can be checked with cat()
        msg_multipart_alternative_body_chr <- str_match(msg_basic_chr, regex(
          "Content-Type: multipart/alternative; boundary=([a-z0-9]{32}).*?\\1.*?\\1.*?\\1--", dotall = TRUE))[1]
        # cat(msg_multipart_alternative_body_chr)
        
# 2. In the email message with attachment(s), convert "multipart/alternative" (created by bogus as.character.mime) into "multipart/mixed" 
        msg_with_att_txt_chr2 <- gsub("multipart/alternative", "multipart/mixed", as.character(msg_with_att_txt))
        # cat(msg_with_att_txt_chr2)
        
# 3. Replace there the text+html body part with the "multipart/alternative" text+html body part extracted from msg_basic at step 1
        msg_matches <- str_match(msg_with_att_txt_chr2,
                                 regex("(.*Content-Type: multipart/mixed; boundary=([a-z0-9]{32}).*?\\2)(.*?\\2.*?)(--\\2.*)", dotall = TRUE))
        msg_with_att_txt_chr3 <- paste0(msg_matches[2], "\r\n", msg_multipart_alternative_body_chr, "\r\n", msg_matches[5])
        # cat(msg_with_att_txt_chr3)
        
# 4. The corrected MIME email message can now be sent successfully !
        gm_send_message(msg_with_att_txt_chr3) # Now this works fine: the .txt attachement is sent together with the text+html body
        
# Same with .pdf
        msg_with_att_pdf_chr2 <- gsub("multipart/alternative", "multipart/mixed", as.character(msg_with_att_pdf))
        msg_matches <- str_match(msg_with_att_pdf_chr2,
                                 regex("(.*Content-Type: multipart/mixed; boundary=([a-z0-9]{32}).*?\\2)(.*?\\2.*?)(--\\2.*)", dotall = TRUE))
        msg_with_att_pdf_chr3 <- paste0(msg_matches[2], "\r\n", msg_multipart_alternative_body_chr, "\r\n", msg_matches[5])
        gm_send_message(msg_with_att_pdf_chr3) # Now this works fine: the .pdf attachement is sent together with the text+html body

[friedlandconsulting]

Experiencing this error myself and it was driving me crazy. Thank you for making it clear what the issue is. Hopefully a new version comes out with the correction!
To note, this happens with more than just .txt and .pdf -- for me it's with .xlsx and .png.

[friedlandconsulting]

Actually a previous bug makes it clear it has to do with when you include both the email_text_body and the email_html_body. If you try with just the email_html_body it should work.