[QP] Correctly find joined fields in the previous stage (#40933)

This logic was trying to match `[name join-alias]` pairs previously, but
that won't work since the later stage field doesn't have a `:join-alias`
on it. This falls back to matching on only the ID or name, but only if
it's unambiguous.

Fixes #40252.

e2e/test/scenarios/models/reproductions/40252-native-model-join-crashes.cy.spec.js

@@ -18,8 +18,7 @@ const modelB = {
   type: "model",
 };
 
-// TODO: unskip when 40252 is fixed
-describe.skip("issue 40252", () => {
+describe("issue 40252", () => {
   beforeEach(() => {
     restore();
     cy.signInAsAdmin();

src/metabase/query_processor/util/add_alias_info.clj

@@ -255,7 +255,12 @@
           (when (string? field-name)
             (when-let [column (m/find-first #(= (:name %) field-name) source-metadata)]
               (let [signature (field-signature (:field_ref column))]
-                (m/find-first #(= (field-signature %) signature) field-exports))))))))
+                (or ;; First try to match with the join alias.
+                    (m/find-first #(= (field-signature %) signature) field-exports)
+                    ;; Then just the names, but if the match is ambiguous, warn and return nil.
+                    (let [matches (filter #(= (second %) field-name) field-exports)]
+                      (when (= (count matches) 1)
+                        (first matches)))))))))))
 
 (defn- matching-field-in-join-at-this-level
   "If `field-clause` is the result of a join *at this level* with a `:source-query`, return the 'source' `:field` clause

test/metabase/query_processor/util/add_alias_info_test.clj

@@ -5,9 +5,11 @@
    [clojure.walk :as walk]
    [metabase.driver :as driver]
    [metabase.driver.h2 :as h2]
+   [metabase.lib.core :as lib]
    [metabase.lib.test-metadata :as meta]
    [metabase.lib.test-util :as lib.tu]
    [metabase.lib.test-util.macros :as lib.tu.macros]
+   [metabase.lib.test-util.metadata-providers.mock :as providers.mock]
    [metabase.query-processor.middleware.fix-bad-references
     :as fix-bad-refs]
    [metabase.query-processor.preprocess :as qp.preprocess]
@@ -772,3 +774,67 @@
                 ::add/source-alias  "CREATED_AT"
                 ::add/desired-alias "Products__CREATED_AT"}]
               (#'add/matching-field-in-join-at-this-level source-query field-clause))))))
+
+(defn- metadata-provider-with-two-models []
+  (let [result-metadata-for (fn [column-name]
+                              {:display_name   column-name
+                               :field_ref      [:field column-name {:base-type :type/Integer}]
+                               :name           column-name
+                               :base_type      :type/Integer
+                               :effective_type :type/Integer
+                               :semantic_type  nil
+                               :fingerprint
+                               {:global {:distinct-count 1, :nil% 0}
+                                :type   #:type{:Number {:min 1, :q1 1, :q3 1, :max 1, :sd nil, :avg 1}}}})]
+    (lib/composed-metadata-provider
+      meta/metadata-provider
+      (providers.mock/mock-metadata-provider
+        {:cards [{:name            "Model A"
+                  :id              1
+                  :database-id     (meta/id)
+                  :type            :model
+                  :dataset-query   {:database (mt/id)
+                                    :type     :native
+                                    :native   {:template-tags {} :query "select 1 as a1, 2 as a2;"}}
+                  :result-metadata [(result-metadata-for "A1")
+                                    (result-metadata-for "A2")]}
+                 {:name            "Model B"
+                  :id              2
+                  :database-id     (meta/id)
+                  :type            :model
+                  :dataset-query   {:database (mt/id)
+                                    :type     :native
+                                    :native   {:template-tags {} :query "select 1 as b1, 2 as b2;"}}
+                  :result-metadata [(result-metadata-for "B1")
+                                    (result-metadata-for "B2")]}
+                 {:name            "Joined"
+                  :id              3
+                  :database-id     (meta/id)
+                  :type            :model
+                  :dataset-query   {:database (meta/id)
+                                    :type     :query
+                                    :query    {:joins
+                                               [{:fields :all,
+                                                 :alias "Model B - A1",
+                                                 :strategy :inner-join,
+                                                 :condition
+                                                 [:=
+                                                  [:field "A1" {:base-type :type/Integer}]
+                                                  [:field "B1" {:base-type :type/Integer, :join-alias "Model B - A1"}]],
+                                                 :source-table "card__2"}],
+                                               :source-table "card__1"}}}]}))))
+
+(deftest ^:parallel models-with-joins-and-renamed-columns-test
+  (testing "an MBQL model with an explicit join and customized field names generate correct SQL (#40252)"
+    (qp.store/with-metadata-provider (metadata-provider-with-two-models)
+      (is (=? {:query {:fields [[:field "A1" {::add/source-table ::add/source
+                                              ::add/source-alias "A1"}]
+                                [:field "A2" {::add/source-table ::add/source
+                                              ::add/source-alias "A2"}]
+                                [:field "B1" {::add/source-table ::add/source
+                                              ::add/source-alias "Model B - A1__B1"}]
+                                [:field "B2" {::add/source-table ::add/source
+                                              ::add/source-alias "Model B - A1__B2"}]]}}
+              (add-alias-info {:type     :query
+                               :database (meta/id)
+                               :query    {:source-table "card__3"}}))))))