Filter empty text parts when streaming

Author: dlarocque

packages/vertexai/src/requests/stream-reader.test.ts

@@ -18,7 +18,8 @@
 import {
   aggregateResponses,
   getResponseStream,
-  processStream
+  processStream,
+  filterEmptyTextParts
 } from './stream-reader';
 import { expect, use } from 'chai';
 import { restore } from 'sinon';
@@ -404,3 +405,29 @@ describe('aggregateResponses', () => {
     });
   });
 });
+
+describe('filterEmptyTextParts', () => {
+  it('Removes only empty text parts', () => {
+    const parts = [
+      {
+        text: 'foo'
+      },
+      {
+        text: ''
+      },
+      {
+        text: 'bar'
+      }
+    ];
+
+    const filteredParts = filterEmptyTextParts(parts);
+    expect(filteredParts).to.deep.equal([
+      {
+        text: 'foo'
+      },
+      {
+        text: 'bar'
+      }
+    ]);
+  });
+});

packages/vertexai/src/requests/stream-reader.ts

@@ -62,6 +62,16 @@ async function getResponsePromise(
       );
       return enhancedResponse;
     }
+
+    // The backend can send empty text parts, but if they are sent back (e.g. in a chat history) there
+    // will be an error. To prevent this, filter out the empty text part from responses.
+    if (value.candidates && value.candidates.length > 0) {
+      value.candidates.forEach(candidate => {
+        if (candidate.content) {
+          candidate.content.parts = candidate.content.parts.filter(part => part.text !== '');
+        }
+      });
+    }
     allResponses.push(value);
   }
 }
@@ -76,6 +86,15 @@ async function* generateResponseSequence(
       break;
     }
 
+    // The backend can send empty text parts, but if they are sent back (e.g. in a chat history) there
+    // will be an error. To prevent this, filter out the empty text part from responses.
+    if (value.candidates && value.candidates.length > 0) {
+      value.candidates.forEach(candidate => {
+        if (candidate.content) {
+          candidate.content.parts = candidate.content.parts.filter(part => part.text !== '');
+        }
+      });
+    }
     const enhancedResponse = createEnhancedContentResponse(value);
     yield enhancedResponse;
   }
@@ -203,3 +222,13 @@ export function aggregateResponses(
   }
   return aggregatedResponse;
 }
+
+/**
+ * The backend can send empty text parts, but if they are sent back (e.g. in a chat history) there
+ * will be an error. To prevent this, filter out the empty text part from responses.
+ *
+ * @internal
+ */
+export function filterEmptyTextParts(parts: Part[]): Part[] {
+  return parts?.filter(part => part.text !== '');
+}