I'm following along the LRU clojure.core.cache guide which yields

(defn get-data [key]
  (cache/lookup (swap! cache-store
                       #(if (cache/has? % key)
                          (cache/hit % key)
                          (cache/miss % key (retrieve-data key))))
                key))

It's also 7pm on a friday, perhaps just needs hammock time 😉

@eriktjacobsen This sounds like a variant of the "cache stampede" issue that someone raised a JIRA ticket about...

https://dev.clojure.org/jira/browse/CCACHE-50

I suggested this as a workaround

(defn get-data [key]
  (let [data (delay (retrieve-data key)]
    (cache/lookup (swap! cache-store cache/through-cache key (fn [_] @data)) key)))

I'm thinking this needs to be baked into the library as a higher-level operation...

I'm also looking at ways to avoid the weird edge case you can get with certain caches where the enclosed has? succeeds but the hit function evicts the item, and then the outside lookup returns nil -- which is surprising at best and annoying at worst.

In particular, it causes clients to include horrors like this: https://github.com/clojure/core.memoize/blob/master/src/main/clojure/clojure/core/memoize.clj#L203-L217

Thanks so much @seancorfield, yes a local delay will work well in this case. Good to know about the has?-evict situation.

what is the equivalent of (.mkdir (java.io.File. "/tmp/crawl/")) on windows?

you can use https://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#createTempDirectory(java.nio.file.Path,%20java.lang.String,%20java.nio.file.attribute.FileAttribute...)

What is equivalent of lein deps with clj and deps.edn? I want to resolve and download dependencies but not run anything (yet).

clj -Sforce < /dev/null

Thanks, it works!

Is there a way to mark a test as pending in clojure.test ?

In clojure.data.json, is there a way to have a default function be called if the object type isn't support? e.g. I simply want to call the .toString method on an object if no built-in JSON encoder is found.

@kenny you could maybe make a function that checks for whether a value implements the JsonWriter protocol and give it to the :value-fn option in clojure.data.json/write-str

@boccato By pending, do you mean you expect it to fail right now, but still want it to run and show up in the results as "N tests were run, A passed, B passed but were expected to fail, C failed but were not expected to" ?

@andy.fingerhut exactly

I am not aware of any feature clojure.test provides to do that, but I haven't even read through all of its docs, so could be ignorant of it. Hopefully someone else will chime in with more info there. @plexus is working on a tool for Clojure testing in the next few months, funded by Clojurists Together. There is an article of what he is planning to do, and a link to contact him at the bottom of the article, here: https://lambdaisland.com/blog/2018-11-02-test-wars-new-hope