Add a MySQL date parser that can handle abbreviated offsets [ci drivers]

Dependong on what timezone you're in, the system_time_zone can be
returned as abbreviated timezone identifier like CST or it can return
an abbreviated offset like -02. This commit adds some special handling
for the offset case.

Fixes #6483

src/metabase/driver.clj

@@ -292,11 +292,19 @@
   [date-format-str]
   (.withOffsetParsed ^DateTimeFormatter (tformat/formatter date-format-str)))
 
+(defn- first-successful-parse
+  "Attempt to parse `time-str` with each of `date-formatters`, returning the first successful parse. If there are no
+  successful parses throws the exception that the last formatter threw."
+  [date-formatters time-str]
+  (or (some #(u/ignore-exceptions (tformat/parse % time-str)) date-formatters)
+      (doseq [formatter (reverse date-formatters)]
+        (tformat/parse formatter time-str))))
+
 (defn make-current-db-time-fn
   "Takes a clj-time date formatter `DATE-FORMATTER` and a native query
   for the current time. Returns a function that executes the query and
   parses the date returned preserving it's timezone"
-  [native-query date-formatter]
+  [native-query date-formatter & more-date-formatters]
   (fn [driver database]
     (let [settings (when-let [report-tz (report-timezone-if-supported driver)]
                      {:settings {:report-timezone report-tz}})
@@ -311,7 +319,7 @@
                          (format "Error querying database '%s' for current time" (:name database)) e))))]
       (try
         (when time-str
-          (tformat/parse date-formatter time-str))
+          (first-successful-parse (cons date-formatter more-date-formatters) time-str))
         (catch Exception e
           (throw
            (Exception.

src/metabase/driver/mysql.clj

@@ -216,6 +216,11 @@
 (def ^:private mysql-date-formatter
   (driver/create-db-time-formatter "yyyy-MM-dd HH:mm:ss.SSSSSS zzz"))
 
+(def ^:private mysql-offset-date-formatter
+  "In some timezones, MySQL doesn't return a timezone description but rather a truncated offset, such as '-02'. That
+  offset will fail to parse using a regular formatter"
+  (driver/create-db-time-formatter "yyyy-MM-dd HH:mm:ss.SSSSSS Z"))
+
 (def ^:private mysql-db-time-query
   "select CONCAT(DATE_FORMAT(current_timestamp, '%Y-%m-%d %H:%i:%S.%f' ), ' ', @@system_time_zone)")
 
@@ -252,7 +257,7 @@
                                                              :display-name "Additional JDBC connection string options"
                                                              :placeholder  "tinyInt1isBit=false"}]))
           :humanize-connection-error-message (u/drop-first-arg humanize-connection-error-message)
-          :current-db-time                   (driver/make-current-db-time-fn mysql-db-time-query mysql-date-formatter)})
+          :current-db-time                   (driver/make-current-db-time-fn mysql-db-time-query mysql-date-formatter mysql-offset-date-formatter)})
 
   sql/ISQLDriver
   (merge (sql/ISQLDriverDefaultsMixin)

test/metabase/driver/mysql_test.clj

@@ -87,6 +87,11 @@
   "America/Los_Angeles"
   (tu/db-timezone-id))
 
+(expect-with-engine :mysql
+  "-02:00"
+  (with-redefs [metabase.driver/execute-query (constantly {:rows [["2018-01-09 18:39:08.000000 -02"]]})]
+    (tu/db-timezone-id)))
+
 (expect (#'mysql/timezone-id->offset-str "US/Pacific")          "-08:00")
 (expect (#'mysql/timezone-id->offset-str "UTC")                 "+00:00")
 (expect (#'mysql/timezone-id->offset-str "America/Los_Angeles") "-08:00")