When I call addField on solr-doc in the let and evaluate solr-doc last I always end up with the exception.

not-understanding-let-oddness.clj

galen.core> (let [solr-doc (SolrInputDocument.)]
    (.getFieldValue solr-doc "id")
    solr-doc)
{}

galen.core> (let [solr-doc (SolrInputDocument.)]
    (.addField solr-doc "id" "xyz")
    solr-doc)
ClassCastException org.apache.solr.common.SolrInputField cannot be cast to java.util.Map$Entry  clojure.core/key (core.clj:1482)

galen.core> (let [solr-doc (SolrInputDocument.) _ (.addField solr-doc "id" "xyz")]
    solr-doc)
ClassCastException org.apache.solr.common.SolrInputField cannot be cast to java.util.Map$Entry  clojure.core/key (core.clj:1482)

galen.core> (let [solr-doc (SolrInputDocument.)]
  (.addField solr-doc "id" "foo"))
nil

I believe this is happening because SolrInputField isn't behaving like a mappy-thing and so the REPL is failing to stringify it sensibly. The code itself operates just fine.

Thanks for this. I ran into the same problem today, and your post helped me out. Your conclusion seems correct.

I added a print-method that just calls toString on SolrInputDocument, and that fixed the problem I was having. Now I can run my code in the REPL without the ClassCastException creeping up.

(defmethod print-method SolrInputDocument [v w]
  (.write w (.toString v)))

I just thought I'd comment in case anybody else experiences this.

Thanks for the comments, I encountered the same issue.