Default viewer for values based on key for associative structures

[Björn Ebbinghaus]

It would be great to be able to assign default viewers to values of associative structures like maps, without using metadata, which often is a pain.

Example:
I use µlog for logging and tracing, a log value may look like this:

{:user-agent nil,
 :mulog/duration 2173538,
 :mulog/namespace "my.namespace",
 :mulog/outcome :ok,
 :mulog/parent-trace nil,
 :http-status 200,
 :mulog/root-trace #mulog/flake "4t1B0IuXNLj7lPIClpVFiSU-MwnVGYs1",
 :mulog/timestamp 1698011013823,
 :uri "/",
 :mulog/trace-id #mulog/flake "4t1B0IuXNLj7lPIClpVFiSU-MwnVGYs1",
 :request-method :get,
 :mulog/event-name :my.namespace/http-request}

It would be great if you could add a key → viewer config to portal, that declares the default viewer for the value of a key.

{:mulog/duration  :portal.viewer/duration-ns
 :mulog/timestamp :portal.viewer/relative-time
 
 ; maybe even a custom view function...
 :mulog/outcome (fn [value] [:span {:style {:color (if (#{:ok} value) "green" "red")}} value])}

I have code that solves this for me, but I think this could be a feature that would be really handy to have in portal itself, as it allows for simple customization, without the hassle of adding metadata to everything.

I would like feedback before I decide if this is something I even could contribute on my own. 🙂

[Chris Badahdah]

@MrEbbinghaus Gotcha, I think this is mostly already supported in Portal via :portal.viewer/for {} in metadata. For example, here is how it's used for portal.nrepl.