Don't allow mapping a model FK to another model (#32146)

* Add `getFields` method to `Database`

* Ensure only real fields returned by `getIdFields`

* Rework to iterate over fields

* Add repro

e2e/test/scenarios/models/reproductions/31663-no-model-fks.cy.spec.js

+import { appBar, main, popover, restore } from "e2e/support/helpers";
+import { SAMPLE_DB_ID } from "e2e/support/cypress_data";
+import { SAMPLE_DATABASE } from "e2e/support/cypress_sample_database";
+
+const { ORDERS_ID, PRODUCTS_ID } = SAMPLE_DATABASE;
+
+// Should be removed once proper model FK support is implemented
+describe("issue 31663", () => {
+  beforeEach(() => {
+    restore();
+    cy.signInAsAdmin();
+
+    cy.intercept("POST", "/api/dataset").as("dataset");
+    cy.intercept("GET", `/api/database/${SAMPLE_DB_ID}/idfields`).as(
+      "idFields",
+    );
+
+    cy.createQuestion({
+      name: "Orders Model",
+      dataset: true,
+      query: { "source-table": ORDERS_ID },
+    });
+
+    cy.createQuestion(
+      {
+        name: "Products Model",
+        dataset: true,
+        query: { "source-table": PRODUCTS_ID },
+      },
+      { visitQuestion: true },
+    );
+  });
+
+  it("shouldn't list model IDs as possible model FK targets (metabase#31663)", () => {
+    // It's important to have product model's metadata loaded to reproduce this
+    appBar().findByText("Our analytics").click();
+
+    main().findByText("Orders Model").click();
+    cy.wait("@dataset");
+    cy.findByLabelText("Move, archive, and more...").click();
+    popover().findByText("Edit metadata").click();
+
+    cy.findByTestId("TableInteractive-root").findByText("Product ID").click();
+    cy.wait("@idFields");
+    cy.findByLabelText("Foreign key target").click();
+    popover().within(() => {
+      cy.findByText("Orders Model → ID").should("not.exist");
+      cy.findByText("Products Model → ID").should("not.exist");
+
+      cy.findByText("Orders → ID").should("exist");
+      cy.findByText("People → ID").should("exist");
+      cy.findByText("Products → ID").should("exist");
+      cy.findByText("Reviews → ID").should("exist");
+    });
+  });
+});

frontend/src/metabase-lib/metadata/Metadata.ts

@@ -65,6 +65,10 @@ class Metadata {
     return Object.values(this.tables);
   }
 
+  fieldsList(): Field[] {
+    return Object.values(this.fields);
+  }
+
   /**
    * @deprecated this won't be sorted or filtered in a meaningful way
    * @returns {Metric[]}

frontend/src/metabase/entities/databases.js

@@ -20,6 +20,8 @@ import {
   getMetadataUnfiltered,
 } from "metabase/selectors/metadata";
 
+import { isVirtualCardId } from "metabase-lib/metadata/utils/saved-questions";
+
 // OBJECT ACTIONS
 export const FETCH_DATABASE_METADATA =
   "metabase/entities/database/FETCH_DATABASE_METADATA";
@@ -81,11 +83,15 @@ const Databases = createEntity({
       _.any(Databases.selectors.getList(state, props), db => db.is_sample),
 
     getIdFields: createSelector(
-      [state => getMetadata(state).fields, (state, props) => props.databaseId],
+      [
+        state => getMetadata(state).fieldsList(),
+        (state, props) => props.databaseId,
+      ],
       (fields, databaseId) =>
-        Object.values(fields).filter(f => {
-          const { db_id } = f.table || {}; // a field's table can be null
-          return db_id === databaseId && f.isPK();
+        fields.filter(field => {
+          const dbId = field?.table?.db_id;
+          const isRealField = !isVirtualCardId(field.table_id);
+          return dbId === databaseId && isRealField && field.isPK();
         }),
     ),
   },

frontend/src/metabase/query_builder/components/DatasetEditor/DatasetFieldMetadataSidebar/SemanticTypePicker/FKTargetPicker.tsx

@@ -93,6 +93,9 @@ function FKTargetPicker({
       onChange={onChange}
       searchable
       searchProp={SEARCH_PROPERTIES}
+      buttonProps={{
+        "aria-label": t`Foreign key target`,
+      }}
       optionValueFn={getOptionValue}
       optionNameFn={getFieldName}
       optionIconFn={getOptionIcon}