## Problem to Solve When using the [mark file as viewed](https://docs.gitlab.com/ee/user/project/merge_requests/reviewing_and_managing_merge_requests.html#mark-files-as-viewed) feature, the viewed checkbox is persisted across files when reviewing in [file-by-file](https://docs.gitlab.com/ee/user/project/merge_requests/reviewing_and_managing_merge_requests.html#file-by-file-diff-navigation) mode.  ## Proposal `Viewed` status should be respected on each file when doing file-by-file review. ## Cause The check for whether a file should be "reviewed" (and collapsed, in this case), is toggled when the `DiffFile` component is mounted. In file-by-file mode, the component is only mounted once, and then the diff file is swapped when moving among files. There also seems to be a problem with sending the `reviewed` status to the file itself at the app level. It's most likely that the app is always interacting with "the first index" (since the single-file view is always index 0), but the reviews have many reviews per MR. That's just a guess, but the `reviewed` property doesn't seem to be updating when you cycle through files. ## Fix The first fix will be to move [this check, in the `mounted` callback for the diff file](https://gitlab.com/gitlab-org/gitlab/-/blob/75f114e374bb048a4d57b2d1bde7ff38ace78f8c/app/assets/javascripts/diffs/components/diff_file.vue#L193-195) into a `'file.id'` listener in the `watch` section of that component. The second fix will be for the checkbox itself, and is a bit more complicated. The `reviewed` property is provided to the `DiffFile` [by the Diffs app](https://gitlab.com/gitlab-org/gitlab/-/blob/75f114e374bb048a4d57b2d1bde7ff38ace78f8c/app/assets/javascripts/diffs/components/app.vue#L526). The available reviews are computed based on [what files are loaded into the app](https://gitlab.com/gitlab-org/gitlab/-/blob/75f114e374bb048a4d57b2d1bde7ff38ace78f8c/app/assets/javascripts/diffs/components/app.vue#L232) at any given time, and then [passed into the file itself as whether it's been `reviewed` (or not)](https://gitlab.com/gitlab-org/gitlab/-/blob/75f114e374bb048a4d57b2d1bde7ff38ace78f8c/app/assets/javascripts/diffs/components/app.vue#L526). This seems to not be updating when navigating between individual files, which may require a tiny bit of investigation and moving this logic somewhere at a higher level (potentially into Vuex).