Prevent custom expressions from being removed from the query (#39518)

e2e/test/scenarios/visualizations-tabular/table-column-settings.cy.spec.js

@@ -496,8 +496,6 @@ describe("scenarios > visualizations > table column settings", () => {
 
       _hideColumn(testData);
       _showColumn(testData);
-      _removeColumn(testData);
-      _addColumn(testData);
     });
 
     it("should be able to show and hide custom expressions for a table with selected fields", () => {
@@ -515,8 +513,6 @@ describe("scenarios > visualizations > table column settings", () => {
 
       _hideColumn(testData);
       _showColumn(testData);
-      _removeColumn(testData);
-      _addColumn(testData);
     });
 
     it("should be able to show and hide columns from aggregations", () => {

frontend/src/metabase/querying/components/FieldPanel/FieldPanel.unit.spec.tsx

@@ -2,7 +2,7 @@ import userEvent from "@testing-library/user-event";
 import { useState } from "react";
 
 import { renderWithProviders, screen } from "__support__/ui";
-import type * as Lib from "metabase-lib";
+import * as Lib from "metabase-lib";
 import { createQuery } from "metabase-lib/test-helpers";
 
 import { FieldPanel } from "./FieldPanel";
@@ -116,6 +116,22 @@ describe("QueryColumnPicker", () => {
     expect(firstColumn).toBeEnabled();
   });
 
+  it("should not allow to remove custom columns", () => {
+    const query = Lib.expression(
+      createQuery(),
+      -1,
+      "Custom",
+      Lib.expressionClause("+", [1, 2]),
+    );
+    setup({ query });
+    const [orderGroup] = screen.getAllByRole("checkbox");
+    const customColumn = screen.getByRole("checkbox", { name: "Custom" });
+    expect(orderGroup).toBeChecked();
+    expect(orderGroup).toBeDisabled();
+    expect(customColumn).toBeChecked();
+    expect(customColumn).toBeDisabled();
+  });
+
   it("should allow to search for columns", () => {
     setup();
     userEvent.type(screen.getByPlaceholderText("Search for a column…"), "a");

frontend/src/metabase/querying/components/FieldPanel/utils.ts

@@ -24,7 +24,10 @@ function getColumnItems(
       column,
       displayName: columnInfo.displayName,
       isSelected: columnInfo.selected ?? false,
-      isDisabled: columnInfo.isAggregation || columnInfo.isBreakout,
+      isDisabled:
+        columnInfo.isAggregation ||
+        columnInfo.isBreakout ||
+        columnInfo.isCalculated,
     };
   });
 }