HTTP 200 or 404 for empty list? - rest

Question

I know this is a fairly common question, but I haven't found an answer that satisfies me.
I've been using django rest framework for a while now, but this is mostly irrelevant other than the example given. Its default behaviour is to return an HTTP 200 with an empty list resource when accessing a route with an empty list of items.
E.g.: if we had a route such as /articles/ to access a list of articles but it contained no items we would get a response like the following json:
{"count":0, "next":null, "previous":null, "items": []}
Which is perfectly fine. We found the resource we were looking for at /articles/, it just happens to have no items in it.
If we access the route /articles/?page=1, we get the exact same response.
So far so good. Now we try to access /articles/?page=2, and the response code changes. Now get get a 404 as if the resource could not be found with an error message saying that the page contains no results. Which is the same case as with ?page=1...
I was perfectly ok with this behaviour, but today I started questioning this design. How is the ?page=1 case different than ?page=2 ? And what's more, how could you tell if the request was "valid" when issuing a HEAD request? Valid in the sense of containing any results.
This could be useful in cases like filtering a list checking the availability of a certain field (for example, issuing a HEAD request to /users/?username=ted).
A 200 response would clearly mean the request was understood and items were found.
A 404 would mean the request was understood, but no items were found at that location/URI (AFAIK the query parameters are also part of the URI)
In case the request could not be understood a 400 would be returned for syntactic errors, and a 422 for semantic errors.
Is this a good design? Why do most people seem to disagree with it and what drawbacks are there in it?

Answer 1

I would go for 200 because the resource is articles.
While querying for ted in users the same applies, users is the resource and as long it is there, a 200 is okay from my point of view.
If you would GET users/ted a 404 would be as good as a 410 (GONE) if a user named ted was there in the past (may better applies to articles than users).

Answer 2

Because we are ok with an empty page1, not ok with an empty page2.
This is driven by the UI consideration (page1 must exist!), nevertheless, it decides the response code.

Answer 3

This really boils down to the "null vs empty collection" argument. The cases for null are also cases for HTTP 404, and the cases for an empty collection are also cases for HTTP 200.
if we had a route such as /articles/ to access a list of articles but it contained no items
Assuming this is a global list of articles, i.e:
http://mywebsite/articles
then this response can never be null, and therefore should never be a 404. The global list of articles always exists, and therefore the collection is always not-null, regardless of whether it contains elements or not.
A simple example here is thinking of a SQL query. If a table exists, even if it's empty, a query will return a result (be it empty or not), so use 200. If the table itself does not exist, you get a query error, so 404.
But if the articles are contained within another resource, e.g. their author:
http://mywebsite/authors/johndoe/articles
Now we get to the part where null (and thus 404) is meaningfully possible.
If johndoe exists and has articles, you return a non-empty list
If johndoe exists and does not have articles, you return an empty list and HTTP status 200
If johndoe does not exist, then you return null and HTTP status 404
This communicates the correct response to the user. 200 reveals that the data was correctly fetched, whereas 404 reveals that the requested resource simply does not exist.
Note that this is slightly different when referring to a specific article instead of a list. When returning a specific resource (or not), instead of a list, 404 is the only correct HTTP status for a 'no item' response.
http://mywebsite/article/1
Here, you either return the article or null.
http://mywebsite/authors/johndoe/articles/1
Here, you return 404 when either author johndoe or article 1 does not exist.

Answer 4

200 simply means the request has succeeded. The information returned with the response is dependent on the method used in the request, for example:
GET an entity corresponding to the requested resource is sent in the response;
HEAD the entity-header fields corresponding to the requested resource are sent in the response without any message-body;
POST an entity describing or containing the result of the action;
TRACE an entity containing the request message as received by the end server.
404 - The server has not found anything matching the Request-URI - In this case I think it means we did not find the page that articles would have been listed on.
So 200 it is. - but perhaps understand what is being returned and format a message that 0 article have been returned.