Don't allow the creation of empty revisions with no changes

CHANGELOG.md

@@ -6,6 +6,7 @@
 - set default document position to (row 1, column 1) on startup (#1568)
 - displays owner name in header message when viewing a notebook you do not own
 - randomly generate initial notebook names (based on a list of iodide compounds) (#1541)
+- don't allow the creation of "empty" revisions on the server
 
 # 0.2.0 (2019-02-28)
 

server/notebooks/serializers.py

@@ -51,6 +51,14 @@ class NotebookRevisionDetailSerializer(serializers.ModelSerializer):
     Details of a revision for a notebook (includes content)
     """
 
+    def validate(self, attrs):
+        last_revision = NotebookRevision.objects.filter(
+            notebook_id=self.context["notebook_id"]
+        ).first()
+        if attrs["title"] == last_revision.title and attrs["content"] == last_revision.content:
+            raise serializers.ValidationError("Revision unchanged from previous")
+        return serializers.ModelSerializer.validate(self, attrs)
+
     class Meta:
         model = NotebookRevision
         fields = ("id", "title", "created", "content")

server/tests/test_notebook_revision_api.py

@@ -144,6 +144,44 @@ def test_create_notebook_revision(fake_user, test_notebook, client):
     test_notebook.refresh_from_db()
     assert test_notebook.title == post_blob["title"]
 
+    # also validate that the response is what we expect
+    assert resp.json() == {
+        "content": post_blob["content"],
+        "created": get_rest_framework_time_string(new_notebook_revision.created),
+        "id": new_notebook_revision.id,
+        "title": post_blob["title"],
+    }
+
+
+def test_dont_create_unmodified_notebook_revision(fake_user, test_notebook, client):
+    client.force_login(user=fake_user)
+
+    # get latest (only) revision for test notebook
+    notebook_revision = NotebookRevision.objects.first()
+    original_creation_time = notebook_revision.created
+    original_id = notebook_revision.id
+
+    # unmodified post
+    unmodified_post_blob = {"title": notebook_revision.title, "content": notebook_revision.content}
+
+    resp = client.post(
+        reverse("notebook-revisions-list", kwargs={"notebook_id": test_notebook.id}),
+        unmodified_post_blob,
+    )
+    assert resp.status_code == 400
+
+    # no new notebook revisions should be created, and the existing (only)
+    # revision should be unchanged
+    assert NotebookRevision.objects.count() == 1
+    notebook_revision = NotebookRevision.objects.first()
+    assert notebook_revision.title == unmodified_post_blob["title"]
+    assert notebook_revision.content == unmodified_post_blob["content"]
+    assert notebook_revision.created == original_creation_time
+    assert notebook_revision.id == original_id
+
+    # be sure that we get the expected error
+    assert resp.json() == {"non_field_errors": ["Revision unchanged from previous"]}
+
 
 def test_delete_notebook_revision_not_logged_in(test_notebook, client):
     # should not be able to delete a notebook revision if not logged in

src/actions/actions.js

@@ -274,22 +274,37 @@ function getNotebookSaveRequestOptions(state, options = undefined) {
 }
 
 function saveNotebookRequest(url, postRequestOptions, dispatch) {
-  return fetchWithCSRFTokenAndJSONContent(url, postRequestOptions)
-    .then(response => {
+  return fetchWithCSRFTokenAndJSONContent(url, postRequestOptions).then(
+    response => {
       if (!response.ok) {
-        throw response;
+        return response
+          .json()
+          .then(json => {
+            // this is a horrible and obvious hack that will go away
+            // when we don't provide an easy interface for the user
+            // to double save a revision (i.e. we have provided
+            // continuous autosave)
+            if (json.non_field_errors && json.non_field_errors.length) {
+              // no changes, not really an error, we'll silently pretend
+              // this didn't happen
+              return {};
+            }
+            // else, some kind of genuine error
+            dispatch(
+              updateAppMessages({
+                message: "Error saving notebook.",
+                messageType: "ERROR_SAVING_NOTEBOOK"
+              })
+            );
+            throw response;
+          })
+          .catch(() => {
+            throw response;
+          });
       }
       return response.json();
-    })
-    .catch(err => {
-      dispatch(
-        updateAppMessages({
-          message: `Error Saving Notebook.`,
-          messageType: "ERROR_SAVING_NOTEBOOK"
-        })
-      );
-      throw new Error(err);
-    });
+    }
+  );
 }
 
 export function createNewNotebookOnServer(options = { forkedFrom: undefined }) {