Fix chat history to exclude content with empty parts

.changeset/icy-waves-attend.md

@@ -0,0 +1,5 @@
+---
+"@google/generative-ai": patch
+---
+
+fix: Exclude content with empty parts from chat history

src/methods/chat-session-helpers.test.ts

@@ -15,9 +15,9 @@
  * limitations under the License.
  */
 
-import { validateChatHistory } from "./chat-session-helpers";
+import { isValidResponse, validateChatHistory } from "./chat-session-helpers";
 import { expect } from "chai";
-import { Content } from "../../types";
+import { Content, GenerateContentResponse } from "../../types";
 import { GoogleGenerativeAIError } from "../errors";
 
 describe("chat-session-helpers", () => {
@@ -167,4 +167,58 @@ describe("chat-session-helpers", () => {
       });
     });
   });
+  describe("isValidResponse", () => {
+    const testCases = [
+      { name: "default response", response: {}, isValid: false },
+      {
+        name: "empty candidates",
+        response: { candidates: [] } as GenerateContentResponse,
+        isValid: false,
+      },
+      {
+        name: "default candidates",
+        response: { candidates: [{}] } as GenerateContentResponse,
+        isValid: false,
+      },
+      {
+        name: "default content",
+        response: { candidates: [{ content: {} }] } as GenerateContentResponse,
+        isValid: false,
+      },
+      {
+        name: "empty parts",
+        response: {
+          candidates: [{ content: { parts: [] } }],
+        } as GenerateContentResponse,
+        isValid: false,
+      },
+      {
+        name: "default part",
+        response: {
+          candidates: [{ content: { parts: [{}] } }],
+        } as GenerateContentResponse,
+        isValid: false,
+      },
+      {
+        name: "part with empty text",
+        response: {
+          candidates: [{ content: { parts: [{ text: "" }] } }],
+        } as GenerateContentResponse,
+        isValid: false,
+      },
+      {
+        name: "part with text",
+        response: {
+          candidates: [{ content: { parts: [{ text: "hello" }] } }],
+        } as GenerateContentResponse,
+        isValid: true,
+      },
+    ];
+
+    testCases.forEach((testCase) => {
+      it(testCase.name, () => {
+        expect(isValidResponse(testCase.response)).to.eq(testCase.isValid);
+      });
+    });
+  });
 });

src/methods/chat-session-helpers.ts

@@ -15,7 +15,12 @@
  * limitations under the License.
  */
 
-import { Content, POSSIBLE_ROLES, Part } from "../../types";
+import {
+  Content,
+  GenerateContentResponse,
+  POSSIBLE_ROLES,
+  Part,
+} from "../../types";
 import { GoogleGenerativeAIError } from "../errors";
 
 type Role = (typeof POSSIBLE_ROLES)[number];
@@ -97,3 +102,28 @@ export function validateChatHistory(history: Content[]): void {
     prevContent = true;
   }
 }
+
+/**
+ * Returns true if the response is valid (could be appended to the history), flase otherwise.
+ */
+export function isValidResponse(response: GenerateContentResponse): boolean {
+  if (response.candidates === undefined || response.candidates.length === 0) {
+    return false;
+  }
+  const content = response.candidates[0]?.content;
+  if (content === undefined) {
+    return false;
+  }
+  if (content.parts === undefined || content.parts.length === 0) {
+    return false;
+  }
+  for (const part of content.parts) {
+    if (part === undefined || Object.keys(part).length === 0) {
+      return false;
+    }
+    if (part.text !== undefined && part.text === "") {
+      return false;
+    }
+  }
+  return true;
+}

src/methods/chat-session.ts

@@ -27,7 +27,7 @@ import {
 } from "../../types";
 import { formatNewContent } from "../requests/request-helpers";
 import { formatBlockErrorMessage } from "../requests/response-helpers";
-import { validateChatHistory } from "./chat-session-helpers";
+import { isValidResponse, validateChatHistory } from "./chat-session-helpers";
 import { generateContent, generateContentStream } from "./generate-content";
 
 /**
@@ -108,11 +108,7 @@ export class ChatSession {
         ),
       )
       .then((result) => {
-        if (
-          result.response.candidates &&
-          result.response.candidates.length > 0 &&
-          result.response.candidates[0]?.content !== undefined
-        ) {
+        if (isValidResponse(result.response)) {
           this._history.push(newContent);
           const responseContent: Content = {
             parts: [],
@@ -180,11 +176,7 @@ export class ChatSession {
       })
       .then((streamResult) => streamResult.response)
       .then((response) => {
-        if (
-          response.candidates &&
-          response.candidates.length > 0 &&
-          response.candidates[0]?.content !== undefined
-        ) {
+        if (isValidResponse(response)) {
           this._history.push(newContent);
           const responseContent = { ...response.candidates[0].content };
           // Response seems to come back without a role set.