Fix - Description for calculated columns in model metadata editing page is...

Fix - Description for calculated columns in model metadata editing page is incorrectly populated with description from other columns (#39851)

* Fix metabase#34349

* Remove outdated comment

* Add repro for metabase#34349

* Add tag for issue 25884 and extract a constant

e2e/test/scenarios/models/reproductions/25884-34349-null-description-in-column-metadata.cy.spec.ts

+import { SAMPLE_DATABASE } from "e2e/support/cypress_sample_database";
+import { openQuestionActions, popover, restore } from "e2e/support/helpers";
+
+const { ORDERS, ORDERS_ID } = SAMPLE_DATABASE;
+
+const ID_DESCRIPTION =
+  "This is a unique ID for the product. It is also called the “Invoice number” or “Confirmation number” in customer facing emails and screens.";
+
+describe("issues 25884 and 34349", () => {
+  beforeEach(() => {
+    restore();
+    cy.signInAsAdmin();
+  });
+
+  it("should show empty description input for columns without description in metadata (metabase#25884, metabase#34349)", () => {
+    cy.createQuestion(
+      {
+        type: "model",
+        query: {
+          "source-table": ORDERS_ID,
+          expressions: {
+            Country: ["substring", "United States", 1, 20],
+          },
+          fields: [
+            ["field", ORDERS.ID, { "base-type": "type/BigInteger" }],
+            ["expression", "Country", { "base-type": "type/Text" }],
+          ],
+          limit: 5, // optimization
+        },
+      },
+      { visitQuestion: true },
+    );
+
+    openQuestionActions();
+    popover().findByText("Edit metadata").click();
+
+    cy.findByLabelText("Description").should("have.text", ID_DESCRIPTION);
+
+    cy.findAllByTestId("header-cell").contains("Country").click();
+    cy.findByLabelText("Description").should("have.text", "");
+
+    cy.findAllByTestId("header-cell").contains("ID").click();
+    cy.findByLabelText("Description").should("have.text", ID_DESCRIPTION);
+  });
+});

frontend/src/metabase/components/form/widgets/FormTextAreaWidget/FormTextAreaWidget.jsx

@@ -23,6 +23,7 @@ const FormTextAreaWidget = ({
       aria-labelledby={`${field.name}-label`}
       tabIndex={tabIndex}
       {...formDomOnlyProps(field)}
+      value={field.value || ""}
     />
     {helperText && (
       <HelpText

frontend/src/metabase/query_builder/containers/test-utils.tsx

@@ -246,7 +246,6 @@ export const setup = async ({
     setupModelIndexEndpoints(card.id, []);
   }
 
-  // this workaround can be removed when metabase#34523 is fixed
   if (card === null) {
     fetchMock.get("path:/api/model-index", [createMockModelIndex()]);
   }