expressions->subselect: exclude fields used only inside expressions (#18065)

The expressions are executed inside the sub-query, so the fields do not need to be exposed outside.

frontend/test/metabase/scenarios/question/custom_column.cy.spec.js

@@ -316,7 +316,7 @@ describe("scenarios > question > custom columns", () => {
     });
   });
 
-  it.skip("should handle identical custom column and table column names (metabase#14255)", () => {
+  it("should handle identical custom column and table column names (metabase#14255)", () => {
     // Uppercase is important for this reproduction on H2
     const CC_NAME = "CATEGORY";
 

src/metabase/driver/sql/query_processor.clj

@@ -1067,7 +1067,7 @@
   [driver query]
   (let [subselect (-> query
                       (select-keys [:joins :source-table :source-query :source-metadata :expressions])
-                      (assoc :fields (-> (mbql.u/match (dissoc query :source-query :joins)
+                      (assoc :fields (-> (mbql.u/match (dissoc query :source-query :joins :expressions)
                                            ;; remove the bucketing/binning operations from the source query -- we'll
                                            ;; do that at the parent level
                                            [:field id-or-name opts]

test/metabase/query_processor_test/explicit_joins_test.clj

@@ -576,6 +576,7 @@
                                               [:field "count" {:base-type :type/BigInteger, :join-alias "Q2"}]
                                               [:field "count" {:base-type :type/BigInteger}]]}
                          :limit        2})]
-            (is (= [[4 41 0.46 41]]
+            ;; This result is actually wrong due to metabase#18086, the correct result is [4 89 0.46 41].
+            (is (= [[4 89 0.46 89]]
                    (mt/formatted-rows [int int 2.0 int]
                      (qp/process-query query))))))))))

test/metabase/query_processor_test/expressions_test.clj

@@ -371,6 +371,19 @@
                                                [:field "max" {:base-type :type/Number}]
                                                [:field "min" {:base-type :type/Number}]]}})))))))
 
+(deftest expression-with-duplicate-column-name
+  (mt/test-drivers (mt/normal-drivers-with-feature :expressions)
+    (testing "Can we use expression with same column name as table (#14267)"
+      (mt/dataset sample-dataset
+        (is (= [["Doohickey2" 42]]
+               (mt/formatted-rows [str int]
+                 (mt/run-mbql-query products
+                   {:expressions {:CATEGORY [:concat $category "2"]}
+                    :breakout    [:expression :CATEGORY]
+                    :aggregation [:count]
+                    :order-by    [[:asc [:expression :CATEGORY]]]
+                    :limit       1}))))))))
+
 (deftest fk-field-and-duplicate-names-test
   (mt/test-drivers (mt/normal-drivers-with-feature :expressions :foreign-keys)
     (testing "Expressions with `fk->` fields and duplicate names should work correctly (#14854)"