Address #31 by improving string representation of reified objects

At least this should give a hint as to what you did wrong...

CHANGELOG.md

@@ -6,6 +6,7 @@ Only accretive/fixative changes will be made from now on.
 
 The following changes have been committed to the **master** branch and will be in the 1.0.0 release:
 
+* Address #31 by making `reify`'d objects produce a more informative string representation if they are printed (e.g., misusing `plan` by not reducing it or not mapping an operation over the rows).
 * Fix #26 by exposing `next.jdbc.result-set/datafiable-result-set` so that various `java.sql.DatabaseMetaData` methods that return result metadata information in `ResultSet`s can be easily turned into a fully realized result set.
 
 ## Stable Builds

src/next/jdbc/connection.clj

@@ -147,7 +147,8 @@
                    (get-driver-connection url
                                           (assoc etc
                                                  :user username
-                                                 :password password)))))
+                                                 :password password)))
+    (toString [_] url)))
 
 (defn- make-connection
   "Given a `DataSource` and a map of options, get a connection and update it

src/next/jdbc/result_set.clj

@@ -343,7 +343,9 @@
       (datafiable-row [this connectable opts]
                       (with-meta
                         (row-builder @builder)
-                        {`core-p/datafy (navize-row connectable opts)})))))
+                        {`core-p/datafy (navize-row connectable opts)}))
+
+      (toString [_] "{row} from `plan` -- missing `map` or `reduce`?"))))
 
 (extend-protocol
   DatafiableRow
@@ -411,7 +413,8 @@
                                                (first sql-params)
                                                (rest sql-params)
                                                opts)]
-                (reduce-stmt stmt f init opts)))))
+                (reduce-stmt stmt f init opts)))
+      (toString [_] "`IReduceInit` from `plan` -- missing reduction?")))
   (-execute-one [this sql-params opts]
     (with-open [stmt (prepare/create this
                                      (first sql-params)
@@ -441,7 +444,8 @@
                                                  (first sql-params)
                                                  (rest sql-params)
                                                  opts)]
-                  (reduce-stmt stmt f init opts))))))
+                  (reduce-stmt stmt f init opts))))
+      (toString [_] "`IReduceInit` from `plan` -- missing reduction?")))
   (-execute-one [this sql-params opts]
     (with-open [con (p/get-connection this opts)]
       (with-open [stmt (prepare/create con
@@ -471,7 +475,8 @@
   (-execute [this _ opts]
     (reify clojure.lang.IReduceInit
       (reduce [_ f init]
-              (reduce-stmt this f init (assoc opts :return-keys true)))))
+              (reduce-stmt this f init (assoc opts :return-keys true)))
+      (toString [_] "`IReduceInit` from `plan` -- missing reduction?")))
   (-execute-one [this _ opts]
     (if-let [rs (stmt->result-set this (assoc opts :return-keys true))]
       (let [builder-fn (get opts :builder-fn as-maps)

test/next/jdbc/connection_test.clj

@@ -66,6 +66,7 @@
     (testing "datasource via Associative"
       (let [ds (p/get-datasource db)]
         (is (instance? javax.sql.DataSource ds))
+        (is (str/index-of (pr-str ds) (str "jdbc:" (:dbtype db))))
         ;; checks get-datasource on a DataSource is identity
         (is (identical? ds (p/get-datasource ds)))
         (with-open [con (p/get-connection ds {})]
@@ -74,6 +75,7 @@
       (let [[url _] (#'c/spec->url+etc db)
             ds (p/get-datasource url)]
         (is (instance? javax.sql.DataSource ds))
+        (is (str/index-of (pr-str ds) url))
         (with-open [con (p/get-connection ds {})]
           (is (instance? java.sql.Connection con)))))
     (testing "connection via map (Object)"

test/next/jdbc_test.clj

@@ -118,3 +118,13 @@ INSERT INTO fruit (name, appearance, cost, grade)
 VALUES ('Pear', 'green', 49, 47)
 "]))))
     (is (= 4 (count (jdbc/execute! (ds) ["select * from fruit"]))))))
+
+(deftest plan-misuse
+  (let [s (pr-str (jdbc/plan (ds) ["select * from fruit"]))]
+    (is (re-find #"missing reduction" s)))
+  (let [s (pr-str (into [] (jdbc/plan (ds) ["select * from fruit"])))]
+    (is (re-find #"missing `map` or `reduce`" s)))
+  (let [s (pr-str (into [] (take 3) (jdbc/plan (ds) ["select * from fruit"])))]
+    (is (re-find #"missing `map` or `reduce`" s)))
+  (is (thrown? IllegalArgumentException
+               (doall (take 3 (jdbc/plan (ds) ["select * from fruit"]))))))