Fix new terms enum API when field meta is not passed for autocomplete value suggestions

src/plugins/data/server/autocomplete/terms_agg.test.ts

@@ -32,6 +32,8 @@ const mockResponse = {
   },
 } as ApiResponse<SearchResponse<any>>;
 
+jest.mock('../index_patterns');
+
 describe('terms agg suggestions', () => {
   beforeEach(() => {
     const requestHandlerContext = coreMock.createRequestHandlerContext();
@@ -86,4 +88,50 @@ describe('terms agg suggestions', () => {
       ]
     `);
   });
+
+  it('calls the _search API with a terms agg and fallback to fieldName when field is null', async () => {
+    const result = await termsAggSuggestions(
+      configMock,
+      savedObjectsClientMock,
+      esClientMock,
+      'index',
+      'fieldName',
+      'query',
+      []
+    );
+
+    const [[args]] = esClientMock.search.mock.calls;
+
+    expect(args).toMatchInlineSnapshot(`
+      Object {
+        "body": Object {
+          "aggs": Object {
+            "suggestions": Object {
+              "terms": Object {
+                "execution_hint": "map",
+                "field": "fieldName",
+                "include": "query.*",
+                "shard_size": 10,
+              },
+            },
+          },
+          "query": Object {
+            "bool": Object {
+              "filter": Array [],
+            },
+          },
+          "size": 0,
+          "terminate_after": 98430,
+          "timeout": "4513ms",
+        },
+        "index": "index",
+      }
+    `);
+    expect(result).toMatchInlineSnapshot(`
+      Array [
+        "whoa",
+        "amazing",
+      ]
+    `);
+  });
 });

src/plugins/data/server/autocomplete/terms_enum.test.ts

@@ -22,6 +22,8 @@ const mockResponse = {
   body: { terms: ['whoa', 'amazing'] },
 };
 
+jest.mock('../index_patterns');
+
 describe('_terms_enum suggestions', () => {
   beforeEach(() => {
     const requestHandlerContext = coreMock.createRequestHandlerContext();
@@ -71,4 +73,45 @@ describe('_terms_enum suggestions', () => {
     `);
     expect(result).toEqual(mockResponse.body.terms);
   });
+
+  it('calls the _terms_enum API and fallback to fieldName when field is null', async () => {
+    const result = await termsEnumSuggestions(
+      configMock,
+      savedObjectsClientMock,
+      esClientMock,
+      'index',
+      'fieldName',
+      'query',
+      []
+    );
+
+    const [[args]] = esClientMock.transport.request.mock.calls;
+
+    expect(args).toMatchInlineSnapshot(`
+      Object {
+        "body": Object {
+          "field": "fieldName",
+          "index_filter": Object {
+            "bool": Object {
+              "must": Array [
+                Object {
+                  "terms": Object {
+                    "_tier": Array [
+                      "data_hot",
+                      "data_warm",
+                      "data_content",
+                    ],
+                  },
+                },
+              ],
+            },
+          },
+          "string": "query",
+        },
+        "method": "POST",
+        "path": "/index/_terms_enum",
+      }
+    `);
+    expect(result).toEqual(mockResponse.body.terms);
+  });
 });

src/plugins/data/server/autocomplete/terms_enum.ts

@@ -36,7 +36,7 @@ export async function termsEnumSuggestions(
       method: 'POST',
       path: encodeURI(`/${index}/_terms_enum`),
       body: {
-        field: field?.name ?? field,
+        field: field?.name ?? fieldName,
         string: query,
         index_filter: {
           bool: {