MLv2 schema should enforce distinct breakouts and fields (#33512)

* MLv2 schema should enforce  distinct breakouts and fields #32489

* Enforce distinct breakouts and fields (#32489)

src/metabase/lib/schema.cljc

@@ -6,7 +6,9 @@
   Some primitives below are duplicated from [[metabase.util.malli.schema]] since that's not `.cljc`. Other stuff is
   copied from [[metabase.mbql.schema]] so this can exist completely independently; hopefully at some point in the
   future we can deprecate that namespace and eventually do away with it entirely."
+  (:refer-clojure :exclude [ref])
   (:require
+   [metabase.lib.options :as lib.options]
    [metabase.lib.schema.aggregation :as aggregation]
    [metabase.lib.schema.common :as common]
    [metabase.lib.schema.expression :as expression]
@@ -50,13 +52,30 @@
    ;; `:native` key), but their definition lives under this key.
    [:template-tags {:optional true} [:ref ::template-tag/template-tag-map]]])
 
+(mr/def ::breakout
+  [:ref ::ref/ref])
+
+(defn- distinct-refs? [refs]
+  (or
+   (< (count refs) 2)
+   (apply
+    distinct?
+    (for [ref refs]
+      (lib.options/update-options ref dissoc :lib/uuid)))))
+
 (mr/def ::breakouts
-  [:sequential {:min 1} [:ref ::ref/ref]])
+  [:and
+   [:sequential {:min 1} ::breakout]
+   [:fn
+    {:error/message "Breakouts must be distinct"}
+    distinct-refs?]])
 
-;;; TODO -- `:fields` is supposed to be distinct (ignoring UUID), e.g. you can't have `[:field {} 1]` in there
-;;; twice. (#32489)
 (mr/def ::fields
-  [:sequential {:min 1} [:ref ::ref/ref]])
+  [:and
+   [:sequential {:min 1} [:ref ::ref/ref]]
+   [:fn
+    {:error/message ":fields must be distinct"}
+    distinct-refs?]])
 
 ;; this is just for enabling round-tripping filters with named segment references
 (mr/def ::filterable

test/metabase/lib/schema_test.cljc

@@ -197,3 +197,19 @@
      {:lib/type :mbql.stage/mbql
       :fields   [[:field {:lib/uuid (str (random-uuid)), :join-alias "A"} 1]]}]
     nil))
+
+(deftest ^:parallel enforce-distinct-breakouts-and-fields-test
+  (let [duplicate-refs [[:field {:lib/uuid "00000000-0000-0000-0000-000000000000"} 1]
+                        [:field {:lib/uuid "00000000-0000-0000-0000-000000000001"} 1]]]
+    (testing #'lib.schema/distinct-refs?
+      (is (not (#'lib.schema/distinct-refs? duplicate-refs))))
+    (testing "breakouts/fields schemas"
+      (are [schema error] (= error
+                             (me/humanize (mc/explain schema duplicate-refs)))
+        ::lib.schema/breakouts ["Breakouts must be distinct"]
+        ::lib.schema/fields    [":fields must be distinct"]))
+    (testing "stage schema"
+      (are [k error] (= error
+                        (me/humanize (mc/explain ::lib.schema/stage {:lib/type :mbql.stage/mbql, k duplicate-refs})))
+        :breakout {:breakout ["Breakouts must be distinct"]}
+        :fields   {:fields [":fields must be distinct"]}))))