monkey_patches.py

#################################################################################################################
# Patch the wagtaildocs.views.documents.edit view so that we keep the same file name if the user uploads a replacement
# with the same filename. The default appends 7 random characters to make the filename unique, which changes the URL.
# 2020-07-10 rrollins: Works with Wagtail 2.9.
# 2020-09-03 cnk: should work with Wagtail 2.11a
# #################################################################################################################
@permission_checker.require('change')
def edit_without_changing_filename(request, document_id):
    Document = get_document_model()
    DocumentForm = get_document_form(Document)

    doc = get_object_or_404(Document, id=document_id)

    if not document_permission_policy.user_has_permission_for_instance(request.user, 'change', doc):
        return permission_denied(request)

    if request.method == 'POST':
        original_file = doc.file
        form = DocumentForm(request.POST, request.FILES, instance=doc, user=request.user)
        if form.is_valid():
            if 'file' in form.changed_data:
                doc = form.save(commit=False)
                doc.file_size = doc.file.size

                # Set new document file hash
                doc.file.seek(0)
                doc._set_file_hash(doc.file.read())
                doc.file.seek(0)
                # BEGIN PATCH
                # Instead of uploading the new file first, and letting it potentially be renamed by the system,
                # rename the _original_ file manually.
                moved_filename = f'{original_file.name}-{uuid4()}'
                original_file.storage.move(original_file.name, moved_filename)
                try:
                    # The file being uploaded will keep its filename, because the original file's name cannot match it.
                    doc.save()
                except Exception as exp:
                    # If anything goes wrong with the upload, rename the original file back to its original name,
                    # then propagate the exception.
                    original_file.storage.move(moved_filename, original_file.name)
                    raise exp
                else:
                    # Saved the new file succeeded, so we can safely delete the original.
                    original_file.storage.delete(moved_filename)
                # END PATCH
            else:
                doc = form.save()

            # Reindex the document to make sure all tags are indexed
            search_index.insert_or_update_object(doc)

            messages.success(request, _("Document '{0}' updated").format(doc.title), buttons=[
                messages.button(reverse('wagtaildocs:edit', args=(doc.id,)), _('Edit'))
            ])
            return redirect('wagtaildocs:index')
        else:
            messages.error(request, _("The document could not be saved due to errors."))
    else:
        form = DocumentForm(instance=doc, user=request.user)

    try:
        local_path = doc.file.path
    except NotImplementedError:
        # Document is hosted externally (eg, S3)
        local_path = None

    if local_path:
        # Give error if document file doesn't exist
        if not os.path.isfile(local_path):
            messages.error(
                request,
                _("The file could not be found. Please change the source or delete the document"),
                buttons=[messages.button(reverse('wagtaildocs:delete', args=(doc.id,)), _('Delete'))]
            )

    return TemplateResponse(request, "wagtaildocs/documents/edit.html", {
        'document': doc,
        'filesize': doc.get_file_size(),
        'form': form,
        'user_can_delete': document_permission_policy.user_has_permission_for_instance(
            request.user, 'delete', doc
        ),
    })
wagtail.documents.views.documents.edit = edit_without_changing_filename