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malli 2025-09-23
igrishaev 2025-09-23T15:21:59.822109Z
Today, I have a big disaster related to malli. I have a very complex schema for parsing incoming data, a kind of DSL. Lots of fields are declared as catn , orn and so on. These fields return pairs like [:integer 123] or [:string "foobar"] for example. When processing them, I have a common pattern like this:
(let [[tag value] parsed]
(case tag
:integer (process-as-integer value)
:string (process-as-string value)))cant,orn and other parsing schemas return not pairs but a custom type Tag which is nothing but a defmap with the following keys:
{:key :integer :value 3000}[:integer 3000] which I had before. Now I'm completely lost: the entire parsing & processing pipeline is broken due to another data format (vector -> map). Just wondering, is there is way to use old-style tags somehow? A flag maybe or something similar?
i believe this was implemented here: https://github.com/metosin/malli/pull/1150
why did you update the version? can you roll back?
igrishaev 2025-09-23T15:28:30.533109Z
This is a matter of several internal libraries. Two or three of them use malli, and someone has pumped it. I can rollback of course but sooner or later somebody do it again
Fwiw, I also ran into this. I basically had to write compatibility for both pre and post versions of this breaking change. At the time I wasn’t able to find a ”feature flag” for compatibility.
Link if you are interested: https://github.com/metosin/oksa/issues/25
igrishaev 2025-09-23T15:33:38.473689Z
I just wanted to stress how upset I am now with that breaking change, and honestly I would never anticipate it from such a good library
I hear you, I would have also hoped for some kind of a flag :) FWIW, I’m ex-metosin, so can’t really reach them, but maybe creating an issue out of this would be a start?
igrishaev 2025-09-23T17:17:31.446209Z
Yeah maybe... I'm thinking if it's possible to extend defrecord such that it supports nth
igrishaev 2025-09-23T17:44:57.043789Z
Actually, this tweak works fine, now the question is, if they OK to accept such a pr:
(defrecord Tag [key value]
clojure.lang.Indexed
(nth [_ i]
(case (long i)
0 key
1 value
(throw (new IndexOutOfBoundsException))))
(nth [_ i not-found]
(case (long i)
0 key
1 value
not-found)))
opqdonut 2025-09-25T09:44:00.346269Z
I'm sorry for the breakage @igrishaev, we could've done a better job highlighting the breakage. I think we underestimated how many people are using parsing this heavily.