Fixes #44

Also adds `assert`s in SQL-generating functions, instead of just 
producing illegal SQL.

CHANGELOG.md

@@ -7,9 +7,12 @@ Only accretive/fixative changes will be made from now on.
 The following changes have been committed to the **master** branch since the 1.0.1 release:
 
 * Fix #45 by adding TimesTen driver support.
+* Fix #44 so that `insert-multi!` with an empty `rows` vector returns `[]`.
 * Fix #42 by adding specs for `execute-batch!` and `set-parameters` in `next.jdbc.prepare`.
 * Fix #41 by improving docstrings and documentation, especially around prepared statement handling.
 * Fix #40 by adding `next.jdbc.prepare/execute-batch!`.
+* Added `assert`s in `next.jdbc.sql` as more informative errors for cases that would generate SQL exceptions (from malformed SQL).
+* Added spec for `:order-by` to reflect what is actually permitted.
 * Expose `next.jdbc.connect/dbtypes` as a table of known database types and aliases, along with their class name(s), port, and other JDBC string components.
 
 ## Stable Builds

src/next/jdbc/specs.clj

@@ -47,7 +47,13 @@
 (s/def ::connectable any?)
 (s/def ::key-map (s/map-of keyword? any?))
 (s/def ::example-map (s/map-of keyword? any? :min-count 1))
-(s/def ::opts-map (s/map-of keyword? any?))
+
+(s/def ::order-by-col (s/or :col keyword?
+                            :dir (s/cat :col keyword?
+                                        :dir #{:asc :desc})))
+(s/def ::order-by (s/coll-of ::order-by-col :kind vector? :min-count 1))
+(s/def ::opts-map (s/and (s/map-of keyword? any?)
+                         (s/keys :opt-un [::order-by])))
 
 (s/def ::transactable any?)
 

src/next/jdbc/sql.clj

@@ -38,6 +38,7 @@
                                         [(conj conds (str e " = ?")) (conj params v)])))
                                   [[] []]
                                   key-map)]
+    (assert (seq where) "key-map may not be empty")
     (into [(str (str/upper-case (name clause)) " "
                 (str/join (if (= :where clause) " AND " ", ") where))]
           params)))
@@ -79,10 +80,11 @@
 (defn- for-order
   "Given an `:order-by` vector, return an `ORDER BY` clause."
   [order-by opts]
-  (if (vector? order-by)
-    (str "ORDER BY "
-         (str/join ", " (map #(for-order-col % opts) order-by)))
-    (throw (IllegalArgumentException. ":order-by must be a vector"))))
+  (when-not (vector? order-by)
+    (throw (IllegalArgumentException. ":order-by must be a vector")))
+  (assert (seq order-by) ":order-by may not be empty")
+  (str "ORDER BY "
+       (str/join ", " (map #(for-order-col % opts) order-by))))
 
 (defn- for-query
   "Given a table name and either a hash map of column names and values or a
@@ -147,6 +149,7 @@
   (let [entity-fn (:table-fn opts identity)
         params    (as-keys key-map opts)
         places    (as-? key-map opts)]
+    (assert (seq key-map) "key-map may not be empty")
     (into [(str "INSERT INTO " (entity-fn (name table))
                 " (" params ")"
                 " VALUES (" places ")")]
@@ -159,7 +162,10 @@
 
   Applies any `:table-fn` / `:column-fn` supplied in the options."
   [table cols rows opts]
-  (assert (apply = (count cols) (map count rows)))
+  (assert (apply = (count cols) (map count rows))
+          "column counts are not consistent across cols and rows")
+  ;; to avoid generating bad SQL
+  (assert (seq rows) "rows may not be empty")
   (let [table-fn  (:table-fn opts identity)
         column-fn (:column-fn opts identity)
         params    (str/join ", " (map (comp column-fn name) cols))
@@ -199,9 +205,11 @@
   ([connectable table cols rows]
    (insert-multi! connectable table cols rows {}))
   ([connectable table cols rows opts]
-   (execute! connectable
-             (for-insert-multi table cols rows opts)
-             (merge {:return-keys true} opts))))
+   (if (seq rows)
+     (execute! connectable
+               (for-insert-multi table cols rows opts)
+               (merge {:return-keys true} opts))
+     [])))
 
 (defn query
   "Syntactic sugar over `execute!` to provide a query alias.

test/next/jdbc/sql_test.clj

@@ -55,9 +55,9 @@
            ["DELETE FROM [user] WHERE id = ? and opt is null" 9]))))
 
 (deftest test-for-update
-  (testing "empty example (SQL error)"
-    (is (= (#'sql/for-update :user {:status 42} {} {:table-fn sql-server :column-fn mysql})
-           ["UPDATE [user] SET `status` = ? WHERE " 42])))
+  (testing "empty example (would be a SQL error)"
+    (is (thrown? AssertionError ; changed in #44
+                 (#'sql/for-update :user {:status 42} {} {:table-fn sql-server :column-fn mysql}))))
   (testing "by example"
     (is (= (#'sql/for-update :user {:status 42} {:id 9} {:table-fn sql-server :column-fn mysql})
            ["UPDATE [user] SET `status` = ? WHERE `id` = ?" 42 9])))
@@ -154,7 +154,11 @@
     (is (= 6 (count (sql/query (ds) ["select * from fruit"]))))
     (is (= {:next.jdbc/update-count 2}
            (sql/delete! (ds) :fruit ["id > ?" 4])))
-    (is (= 4 (count (sql/query (ds) ["select * from fruit"]))))))
+    (is (= 4 (count (sql/query (ds) ["select * from fruit"])))))
+  (testing "empty insert-multi!" ; per #44
+    (is (= [] (sql/insert-multi! (ds) :fruit
+                                 [:name :appearance :cost :grade]
+                                 [])))))
 
 (deftest no-empty-example-maps
   (is (thrown? clojure.lang.ExceptionInfo
@@ -163,3 +167,9 @@
                (sql/update! (ds) :fruit {} {})))
   (is (thrown? clojure.lang.ExceptionInfo
                (sql/delete! (ds) :fruit {}))))
+
+(deftest no-empty-order-by
+  (is (thrown? clojure.lang.ExceptionInfo
+               (sql/find-by-keys (ds) :fruit
+                                 {:name "Apple"}
+                                 {:order-by []}))))