Structured QP now returns useful error responses

src/metabase/driver/generic_sql/query_processor.clj

@@ -47,10 +47,16 @@
   {:pre [(integer? (:database query)) ; double check that the query being passed is valid
          (map? (:query query))
          (= (name (:type query)) "query")]}
-  (->> (process query)
-       eval
-       (post-process query)
-       (annotate/annotate query)))
+  (try
+    (->> (process query)
+         eval
+         (post-process query)
+         (annotate/annotate query))
+    (catch java.sql.SQLException e
+      {:status :failed
+       :error (->> (.getMessage e)                       ; error message comes back like "Error message ... [status-code]
+                   (re-find  #"(?s)(^.*)\s+\[[\d-]+\]$") ; status code isn't useful and makes unit tests hard to write so strip it off
+                   second)})))                           ; (?s) = Pattern.DOTALL - tell regex `.` to match newline characters as well
 
 
 (defn process-and-run

test/metabase/driver/generic_sql/query_processor_test.clj

@@ -436,3 +436,18 @@
       ;; Rows come back like `[value timestamp]` but it is hard to compare timestamps directly since the values that come back are casted
       ;; to Dates and the exact value depends on the locale of the machine running the tests. So just drop the timestamps from the results.
       (update-in [:data :rows] (partial map first))))
+
+
+;; # ERROR RESPONSES
+
+;; Check that we get an error response formatted the way we'd expect
+(expect
+    {:status :failed
+     :error "Column \"CHECKINS.NAME\" not found; SQL statement:\nSELECT \"CHECKINS\".* FROM \"CHECKINS\" WHERE (\"CHECKINS\".\"NAME\" = ?)"}
+  (process-and-run {:database @db-id
+                    :type :query
+                    :query {:source_table (table->id :checkins)
+                            :filter ["=" (field->id :venues :name) 1] ; wrong Field
+                            :aggregation ["rows"]
+                            :breakout [nil]
+                            :limit nil}}))