mail_composer_attachment_selector

Odoo's email composer keeps its footer minimal: Send, Discard, a template picker, a schedule button, and a paperclip. That paperclip is this widget. It is registered on the composer's attachment_ids field but renders no pills, no list, and no preview, just a button wrapping Odoo's FileUploader component with multiUpload enabled.

When files are picked, each one is converted from its data URL to a File object and handed to the mail.attachment_upload service, which uploads it against the thread the message will be posted to. The resulting attachment id is then linked into attachment_ids through an x2many command, so the wizard record carries the attachment when the message is sent.

For users this is invisible plumbing, which is the point: attach a file, hit send, and the file ends up on the right record's thread rather than orphaned in a wizard. For teams customizing the composer, the widget matters for the opposite reason. Because it resolves the target thread itself, from the composer's model and res_ids values or the active ids in context, any custom wizard that borrows this widget must supply those values or uploads will attach to the wrong thread.

It is also a useful pattern to copy: a many2many to ir.attachment rendered as nothing but an upload button is a clean UX for wizards where the file list is displayed elsewhere or not at all.

The core pattern: composer footer

<footer>
    <button string="Send" name="action_send_mail" type="object"/>
    <field name="attachment_ids"
           widget="mail_composer_attachment_selector"
           invisible="not can_edit_body"/>
</footer>

This mirrors mail_compose_message_views.xml in Odoo 19: the button hides entirely when the template body is not editable.

Scheduled message form

<field name="attachment_ids" widget="mail_composer_attachment_selector"/>
<field name="scheduled_date" widget="datetime_scheduled_date"/>

On mail.scheduled.message the widget takes the target record from res_id instead of res_ids, the second of its two hardcoded model checks.

The upload path depends on which model the widget sits on. On the composer wizard, it parses res_ids as JSON, falling back to context.active_ids because the composer stops storing ids past a size limit, and always uploads against the first id. On mail.scheduled.message, it reads the single res_id relation instead.

The second branch exists because of a bug fixed in 19. The uploader service pushes each attachment into a composer object, and in Odoo 18 that was always the thread's own composer, which the chatter observes. Scheduling a message with an attachment therefore made the file appear inside the record's live chatter composer as a leftover. Odoo 19 passes a throwaway { attachments: [] } object for scheduled messages, with a source comment spelling out the reason. If you see that symptom on 18, it is this, not your customization.

Odoo 20 is expected at Odoo Experience in Brussels, 24 to 26 September 2026. The development branch is unstable and everything below is provisional until release, when this page is re-verified.

Three changes are visible at the time of writing. The thread model resolution gains a fallback, record.data.model || context.active_model, which makes the widget usable in wizards that never store a model field. The store access moves from mailStore.Thread to mailStore["mail.thread"], relevant to anyone patching the upload flow. And the paperclip swaps from FontAwesome to the new oi icon set with data-icon="attach_file", so CSS targeting fa-paperclip in a customized composer will stop matching.