Example error messages from common mistakes with Datomic

errors.clj

;; Some example error messages resulting from common mistakes
;; using Datomic 0.8.4138

(ns errors
  (:use [datomic.api :as d :only (db q)]))

(def uri "datomic:mem://database")

(d/create-database uri)

(def conn (d/connect uri))

(defn find-attribute [keyword]
  (q '[:find ?attr :in $ ?name :where [?attr :db/ident ?name]]
     (db conn)
     keyword))


(comment
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; OK:
  (find-attribute :db/cardinality)

  ;; If I mistakenly pass a nil as an input:
  (find-attribute nil)
  ;; Exception Unable to find data source: $234 in: ($234 $)
  ;; datomic.datalog/eval-rule/fn--4697 (datalog.clj:968)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

  ;; OK:
  (d/transact conn [[:db/add (d/tempid :db.part/user) :db/ident :foo]])

  ;; If I mistakenly add an extra layer of nesting:
  (d/transact conn [[[:db/add (d/tempid :db.part/user) :db/ident :foo]]])
  ;; ExceptionInfo :db/bad-keyword Can't find config/Symbolish support
  ;; for: [:db/add #db/id[:db.part/user -1000001] :db/ident :foo] of
  ;; class: class clojure.lang.PersistentVector clojure.core/ex-info
  ;; (core.clj:4327)

  ;; If I mistakenly commit a nil:
  (d/transact conn [[nil]])
  ;; ExceptionInfo :transact/bad-data Unable to resolve data function:
  ;; clojure.core/ex-info (core.clj:4327)

  )

\o/