Use keyword as datetime-diff units (#30439)

* Use keyword as datetime-diff units

Fixes #29897.

* Fix MLv2 round trip test

Fields with :base-type :type/Text are not considered temporal expressions
therefore :datetime-diff with such arguments is not a valid expression.
Such expressions removed by the clean step of the conversion to pMBQL.

src/metabase/lib/schema/expression/temporal.cljc

@@ -33,7 +33,7 @@
 (mbql-clause/define-tuple-mbql-clause :datetime-diff :- :type/Integer
   #_:datetime1 [:schema [:ref ::expression/temporal]]
   #_:datetime2 [:schema [:ref ::expression/temporal]]
-  #_:unit [:enum "year" "month" "day" "hour" "second" "millisecond" "quarter"])
+  #_:unit [:ref ::temporal-bucketing/unit.date-time.truncate])
 
 (mbql-clause/define-tuple-mbql-clause :get-week :- :type/Integer
   #_:datetime [:schema [:ref ::expression/temporal]]

test/metabase/query_processor_test/date_time_zone_functions_test.clj

@@ -1043,13 +1043,13 @@
                                {:database (mt/id)
                                 :type     :query
                                 :query    {:filter [:and
-                                                    [:= a-str [:field "a_dt_tz_text" {:base-type :type/Text}]]
-                                                    [:= b-str [:field "b_dt_tz_text" {:base-type :type/Text}]]]
+                                                    [:= a-str [:field "a_dt_tz_text" {:base-type :type/DateTime}]]
+                                                    [:= b-str [:field "b_dt_tz_text" {:base-type :type/DateTime}]]]
                                            :expressions  (into {}
                                                                (for [unit units]
                                                                  [(name unit) [:datetime-diff
-                                                                               [:field "a_dt_tz" {:base-type :type/Text}]
-                                                                               [:field "b_dt_tz" {:base-type :type/Text}]
+                                                                               [:field "a_dt_tz" {:base-type :type/DateTime}]
+                                                                               [:field "b_dt_tz" {:base-type :type/DateTime}]
                                                                                unit]]))
                                            :fields       (into [] (for [unit units]
                                                                     [:expression (name unit)]))

test/metabase/query_processor_test/test_mlv2.clj

@@ -35,10 +35,6 @@
   [legacy-query]
   (or
    *skip-conversion-tests*
-   ;; #29897: `:datetime-diff` is not handled correctly.
-   (mbql.u/match-one legacy-query
-     :datetime-diff
-     "#29897")
    ;; #29904: `:fields` in `:joins` are supposed to be returned even if `:fields` is specified.
    (mbql.u/match-one legacy-query
      {:fields fields, :joins joins}