fix(dataset): preserve validation error messages (#43631)

Co-authored-by: Matt Fitzgerald <matt.fitzgerald@preset.io>

superset-frontend/packages/superset-ui-core/src/query/getClientErrorObject.ts

@@ -119,6 +119,20 @@ export function retrieveErrorMessage(
   return statusError || parseStringResponse(str);
 }
 
+function getFirstValidationError(message: JsonObject): string | undefined {
+  const [firstError] = Object.values(message);
+
+  if (typeof firstError === 'string') {
+    return firstError;
+  }
+
+  if (Array.isArray(firstError)) {
+    return firstError.find((item): item is string => typeof item === 'string');
+  }
+
+  return undefined;
+}
+
 export function parseErrorJson(responseJson: JsonObject): ClientErrorObject {
   let error = { ...responseJson };
   // Backwards compatibility for old error renderers with the new error object
@@ -126,13 +140,12 @@ export function parseErrorJson(responseJson: JsonObject): ClientErrorObject {
     error.error = error.description = error.errors[0].message;
     error.link = error.errors[0]?.extra?.link;
   }
-  // Marshmallow field validation returns the error message in the format
-  // of { message: { field1: [msg1, msg2], field2: [msg], } }
+  // Marshmallow field validation returns arrays for string messages, but
+  // serializes lazy translation messages as strings instead.
   if (!error.error && error.message) {
     if (typeof error.message === 'object') {
       error.error =
-        Object.values(error.message as Record<string, string[]>)[0]?.[0] ||
-        t('Invalid input');
+        getFirstValidationError(error.message) || t('Invalid input');
     }
     if (typeof error.message === 'string') {
       if (checkForHtml(error.message)) {

superset-frontend/packages/superset-ui-core/test/query/getClientErrorObject.test.ts

@@ -244,6 +244,24 @@ test('parseErrorJson with message', () => {
   });
 });
 
+test('parseErrorJson preserves string-valued validation messages', () => {
+  const calculatedColumnError =
+    'Custom SQL fields cannot be parsed as a single SQL statement.';
+
+  expect(
+    parseErrorJson({
+      message: {
+        'columns.0.expression': calculatedColumnError,
+      },
+    }),
+  ).toEqual({
+    message: {
+      'columns.0.expression': calculatedColumnError,
+    },
+    error: calculatedColumnError,
+  });
+});
+
 test('parseErrorJson with HTML message', () => {
   expect(
     parseErrorJson({