>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #3122389. --> Reported by: [adamps](https://www.drupal.org/user/2650563) >>> <h3>Problem description</h3> <p>For each mail sent, this module needs to compare the requested format (plain text/HTML) with the current format and maybe perform some conversion. Currently there are several bugs with this.</p> <p>Part of the cause of these bugs is confusion over how to know the current format. I propose that the only reliable way is the standard "safe-markup" mechanism used throughout Drupal: if the content implements <code>MarkupInterface</code> then it is safe markup; if not then it must be escaped if used in HTML context.</p> <p>We can look at each of the 4 possible cases in turn:</p> <p>1. Input plain, output plain<br> - Correct: do nothing<br> - Actual: if the content contains characters that resemble HTML tags it will be treated as HTML and corrupted</p> <p>2. Input plain, output HTML<br> - Correct: HTML encode (and possibly a little more filtering)<br> - Actual: since <span class="drupalorg-gitlab-issue-link drupalorg-gitlab-link-wrapper"><a href="https://git.drupalcode.org/project/swiftmailer/-/work_items/2937293" class="drupalorg-gitlab-link">https://git.drupalcode.org/project/swiftmailer/-/work_items/2937293</a></span> code will call <code>MailFormatHelper::htmlToText()</code> instead.</p> <p>3. Input HTML, output plain<br> - Correct: convert HTML to text<br> - Actual: no conversion</p> <p>4. Input HTML, output HTML<br> - Correct: do nothing<br> - Actual: if the input contains no tags it will be HTML escaped leading to double-encoding of entities</p> <p>1. and 4. were introduced by <span class="drupalorg-gitlab-issue-link drupalorg-gitlab-link-wrapper"><a href="https://git.drupalcode.org/project/swiftmailer/-/work_items/2831959" class="drupalorg-gitlab-link">https://git.drupalcode.org/project/swiftmailer/-/work_items/2831959</a></span>. 3. Has been present for a long time as far as I can see.</p> <p>These are objective clear bugs and we can fix all of them without any disadvantages that I can see.</p> <h4>Secondary problems</h4> <p>In contrast these are more subjective points, and fixing them would perhaps have downsides for some users, or would be non-back-compatible. Now split into separate issues.</p> <ol> <li><span class="drupalorg-gitlab-issue-link project-issue-status-info project-issue-status-7"><a href="https://www.drupal.org/project/swiftmailer/issues/3125041" title="Status: Closed (fixed)">#3125041: Clarify and simplify message settings</a></span></li> <li><span class="drupalorg-gitlab-issue-link project-issue-status-info project-issue-status-1"><a href="https://www.drupal.org/project/swiftmailer/issues/3125042" title="Status: Active">#3125042: [META] New &amp; improved format conversions</a></span></li> </ol> <h3>Proposed resolution</h3> <p>In the first case let's set aside the secondary problems. Therefore correct code for SwiftMailer::massageMessageBody() is </p> <ol> <li>If input is markup and output is plain, then call <code>MailFormatHelper::htmlToText()</code></li> <li>If input is plain and output is HTML, then apply the plain text filter</li> </ol> <p>We should write some better tests, but that's not possible until fixing <span class="drupalorg-gitlab-issue-link project-issue-status-info project-issue-status-7"><a href="https://www.drupal.org/project/simplenews/issues/3106374" title="Status: Closed (fixed)">#3106374: Count error if translation is missing</a></span>.</p>