Post History

Proposal: filters for post lists

Several discussions have touched on the idea of being able to filter the contents of the post list.  Whether your goal is to [find unanswered questions](https://meta.codidact.com/posts/285245), [hide closed questions](https://meta.codidact.com/posts/285216), [hide ignored tags](https://meta.codidact.com/posts/284720), or build a more complex filter, this is something we've wanted to be able to support for a while.  A [design mockup](https://meta.codidact.com/posts/282101) earlier this year showed one possible approach.

I have some ideas for how we could approach this feature and I'd like to hear what y'all think.  Please note that this is a proposal; where I use language like "you can", I mean that's how I imagine this working, not that I'm promising that specific behavior.  (I'm not in a position to make promises like that.)

Key idea #1: **anything you can define in a filter, you can also search for, but not necessarily the other way around.**  Our [search interface](https://meta.codidact.com/help/search) is pretty  expressive (there's always more to do), and it would be silly to write a *second* search-like thing.  Filters will be implemented on top of search.  If we need to expand the search language, we will.

That said, there are searches you can do that don't make sense as filters for the post list -- for example, you can search specifically for answers.  Filters are a subset of search.

Key idea #2: **filters can be defined, named, and reused, and we'll provide some built-in ones**. "Unanswered questions" seems like one that would be popular, for example.  And if you want to *refine* the built-in "unanswered questions" filter (for example), you can.  

You'll have access to all your defined filters in all categories and on all communities -- so if you want to have that meta "exclude status-completed" filter, you only have to write it once.  When you choose a filter for a category, it'll stay that way until you choose another (or clear it).

Key idea #3: **filters are based on properties of the posts, not properties of the users (at least for now)**.  This is both a performance consideration and a complexity consideration.  "Questions asked by new users" or "questions answered by people whose answers I tend to upvote" aren't really workable, I don't think.  After we have something built and people are using it, if this is posing a problem we can revisit it then.  Sure, it's all SQL under the hood, but we don't want to jump straight there.

Note that "my favorite tags" or "my ignored tags" would be ok -- that's just a shorthand for "posts with (or without) these tags".  Those are properties of the posts.

Key idea #4: **start simple, then expand**.  Ultimately, we might find people wanting to write filters with complex boolean expressions based on scores, ages of posts, numbers of answers, scores of answers, tags, "questions I haven't answered", and more.  We don't know everything that will be needed or requested.  By basing it on search from the beginning, I think we avoid making early decisions that would preclude future expansion. I'd rather refine and if necessary rework the UI later than try to build the giant union of all things that might be needed at the beginning. We're going to learn as we go, together, based on your feedback; let's take an iterative approach.

**Enough talk; show me a picture.**

I see filters as going in the right column (on the desktop site; mobile would be behind a button most likely).  There would be a "filter" widget that, by default, just shows the selector, like this:

![filter selector, current value "no filter selected"](https://meta.codidact.com/uploads/ukXNcyYeA6Kp9zeTdnYHRLbq)

When you select a filter, the widget would expand to show its definition.  This would include all the parts that can be customized, even if the current filter doesn't set them, so that you'll have access to them.  For example:

!["Unanswered": question status open, answers 0, spaces for score/age/when active/tags, "save as" button](https://meta.codidact.com/uploads/UR1a2Np5KoJ9ekh8wgZ3Xzg5)

If you edit the filter, the UI would somehow signal that you have unsaved changes and enable the "save as" button.  I haven't given enough thought to the UI around "save" (edit) versus "save as" (clone and modify), and maybe a "save as" button isn't the right way to do this, but the goal would be to support both editing your own existing filters and creating new filters.

**I don't know if this is the right list of filter properties.**  It's a first draft.

A post list is not necessarily *questions*; it could be articles, articles *and* questions, or other post types not yet defined.  We'll need to offer only the filters that make sense for the current post list.  I used questions in my examples here because that's what's most common.

----

What feedback do y'all have?  What did I not get quite right, what did I miss, and what do we need to be thinking about that we aren't yet?