support multipart email (#48)

Co-authored-by: Dawid Dziurla <dawidd0811@gmail.com>

README.md

@@ -8,27 +8,32 @@ An action that simply sends a mail to multiple recipients.
 - name: Send mail
   uses: dawidd6/action-send-mail@v2
   with:
+    # Required mail server address:
     server_address: smtp.gmail.com
+    # Required mail server port:
     server_port: 465
+    # Required mail server username:
     username: ${{secrets.MAIL_USERNAME}}
+    # Required mail server password:
     password: ${{secrets.MAIL_PASSWORD}}
+    # Required mail subject:
     subject: Github Actions job result
-    # Literal body:
+    # Required recipients' addresses:
-    body: Build job of ${{github.repository}} completed successfully!
-    # Read file contents as body:
-    body: file://README.md
     to: obiwan@example.com,yoda@example.com
+    # Required sender information (address can be skipped):
     from: Luke Skywalker # <user@example.com>
-    # Optional carbon copy recipients
+    # Optional plain body:
+    body: Build job of ${{github.repository}} completed successfully!
+    # Optional HTML body read from file:
+    html_body: file://README.html
+    # Optional carbon copy recipients:
     cc: kyloren@example.com,leia@example.com
-    # Optional blind carbon copy recipients
+    # Optional blind carbon copy recipients:
     bcc: r2d2@example.com,hansolo@example.com
-    # Optional recipient of the email response
+    # Optional recipient of the email response:
     reply_to: luke@example.com
     # Optional unsigned/invalid certificates allowance:
     ignore_cert: true
-    # Optional content type (defaults to text/plain):
-    content_type: text/html
     # Optional converting Markdown to HTML (set content_type to text/html too):
     convert_markdown: true
     # Optional attachments:

action.yml

@@ -20,15 +20,18 @@ inputs:
   subject:
     description: Subject of mail message
     required: true
-  body:
-    description: Body of mail message (might be a filename prefixed with file:// to read from)
-    required: true
   to:
     description: Recipients mail addresses (separated with comma)
     required: true
   from:
     description: Full name of mail sender (might be with an email address specified in <>)
     required: true
+  body:
+    description: Body of mail message (might be a filename prefixed with file:// to read from)
+    required: false
+  html_body:
+    description: HTML body of mail message (might be a filename prefixed with file:// to read from)
+    required: false
   cc:
     description: Carbon copy recipients (separated with comma)
     required: false
@@ -41,10 +44,6 @@ inputs:
   ignore_cert:
     description: Allow unsigned/invalid certificates
     required: false
-  content_type:
-    description: Content-Type HTTP header (text/html or text/plain)
-    required: false
-    default: text/plain
   convert_markdown:
     description: Convert body from Markdown to HTML (set content_type input as text/html too)
     required: false

main.js

@@ -36,13 +36,13 @@ async function main() {
         const username = core.getInput("username", { required: true })
         const password = core.getInput("password", { required: true })
         const subject = core.getInput("subject", { required: true })
-        const body = core.getInput("body", { required: true })
         const from = core.getInput("from", { required: true })
         const to = core.getInput("to", { required: true })
+        const body = core.getInput("body", { required: false })
+        const htmlBody = core.getInput("html_body", { required: false })
         const cc = core.getInput("cc", { required: false })
         const bcc = core.getInput("bcc", { required: false })
         const replyTo = core.getInput("reply_to", { required: false })
-        const contentType = core.getInput("content_type", { required: true })
         const attachments = core.getInput("attachments", { required: false })
         const convertMarkdown = core.getInput("convert_markdown", { required: false })
         const ignoreCert = core.getInput("ignore_cert", { required: false })
@@ -63,12 +63,12 @@ async function main() {
         const info = await transport.sendMail({
             from: getFrom(from, username),
             to: to,
+            subject: subject,
             cc: cc ? cc : undefined,
             bcc: bcc ? bcc : undefined,
             replyTo: replyTo ? replyTo : undefined,
-            subject: subject,
+            text: body ? getBody(body, convertMarkdown) : undefined,
-            text: contentType != "text/html" ? getBody(body, convertMarkdown) : undefined,
+            html: htmlBody ? getBody(htmlBody, convertMarkdown) : undefined,
-            html: contentType == "text/html" ? getBody(body, convertMarkdown) : undefined,
             attachments: attachments ? attachments.split(',').map(f => ({ path: f.trim() })) : undefined
         })
     } catch (error) {