[ML] Data frames: Fix source table for cells of type object. (#41234) (#41319)

- Fixes a possible crash of the data frames source index table.
- While the source document field structure was already flattened to avoid displaying nested objects in table cells, this failed to catch if a field itself was of type object, for example geo fields.
- Similar to how complex arrays were already handled, this adds a check to display a object badge with a tooltip if the cell value is of type object and not suitable to display the raw value.
- This fixes an issue reported when the full raw object structure of tweets was used as a source index to create a data frame.

x-pack/legacy/plugins/ml/public/data_frame/components/source_index_preview/__snapshots__/source_index_preview.test.tsx.snap

@@ -0,0 +1,33 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Data Frame: <SourceIndexPreview /> Minimal initialization 1`] = `
+<div>
+  <ContextProvider
+    value={
+      Object {
+        "combinedQuery": Object {},
+        "currentIndexPattern": Object {
+          "fields": Array [],
+          "id": "the-index-pattern-id",
+          "title": "the-index-pattern-title",
+        },
+        "currentSavedSearch": Object {},
+        "indexPatterns": Object {},
+        "kbnBaseUrl": "url",
+        "kibanaConfig": Object {},
+      }
+    }
+  >
+    <Component
+      query={
+        Object {
+          "query_string": Object {
+            "default_operator": "AND",
+            "query": "the-query",
+          },
+        }
+      }
+    />
+  </ContextProvider>
+</div>
+`;

x-pack/legacy/plugins/ml/public/data_frame/components/source_index_preview/source_index_preview.test.tsx

@@ -0,0 +1,53 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
+import { shallow } from 'enzyme';
+import React from 'react';
+
+import { getPivotQuery, KibanaContext } from '../../common';
+
+import { SourceIndexPreview } from './source_index_preview';
+
+// workaround to make React.memo() work with enzyme
+jest.mock('react', () => {
+  const r = jest.requireActual('react');
+  return { ...r, memo: (x: any) => x };
+});
+
+describe('Data Frame: <SourceIndexPreview />', () => {
+  test('Minimal initialization', () => {
+    const currentIndexPattern = {
+      id: 'the-index-pattern-id',
+      title: 'the-index-pattern-title',
+      fields: [],
+    };
+
+    const props = {
+      query: getPivotQuery('the-query'),
+    };
+
+    // Using a wrapping <div> element because shallow() would fail
+    // with the Provider being the outer most component.
+    const wrapper = shallow(
+      <div>
+        <KibanaContext.Provider
+          value={{
+            combinedQuery: {},
+            currentIndexPattern,
+            currentSavedSearch: {},
+            indexPatterns: {},
+            kbnBaseUrl: 'url',
+            kibanaConfig: {},
+          }}
+        >
+          <SourceIndexPreview {...props} />
+        </KibanaContext.Provider>
+      </div>
+    );
+
+    expect(wrapper).toMatchSnapshot();
+  });
+});

x-pack/legacy/plugins/ml/public/data_frame/components/source_index_preview/source_index_preview.tsx

@@ -245,7 +245,37 @@ export const SourceIndexPreview: React.SFC<Props> = React.memo(({ cellClick, que
               }
             )}
           >
-            <EuiBadge>array</EuiBadge>
+            <EuiBadge>
+              {i18n.translate(
+                'xpack.ml.dataframe.sourceIndexPreview.dataFrameSourceIndexArrayBadgeContent',
+                {
+                  defaultMessage: 'array',
+                }
+              )}
+            </EuiBadge>
+          </EuiToolTip>
+        );
+      } else if (typeof d === 'object' && d !== null) {
+        // If the cells data is an object, display a 'object' badge with a
+        // tooltip that explains that this type of field is not supported in this table.
+        return (
+          <EuiToolTip
+            content={i18n.translate(
+              'xpack.ml.dataframe.sourceIndexPreview.dataFrameSourceIndexObjectToolTipContent',
+              {
+                defaultMessage:
+                  'The full content of this object based column is available in the expanded row.',
+              }
+            )}
+          >
+            <EuiBadge>
+              {i18n.translate(
+                'xpack.ml.dataframe.sourceIndexPreview.dataFrameSourceIndexObjectBadgeContent',
+                {
+                  defaultMessage: 'object',
+                }
+              )}
+            </EuiBadge>
           </EuiToolTip>
         );
       }