aws[patch]: Fix error when processing empty string chunk conent

langchain-ai · Jul 18, 2024 · ca624aa · ca624aa
1 parent 9b6a764
commit ca624aa
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Showing 2 changed files with 38 additions and 6 deletions.
diff --git a/libs/langchain-aws/src/common.ts b/libs/langchain-aws/src/common.ts
@@ -381,7 +381,7 @@ export function handleConverseStreamContentBlockDelta(
   if (!contentBlockDelta.delta) {
     throw new Error("No delta found in content block.");
   }
-  if (contentBlockDelta.delta.text) {
+  if (typeof contentBlockDelta.delta.text === "string") {
     return new ChatGenerationChunk({
       text: contentBlockDelta.delta.text,
       message: new AIMessageChunk({
@@ -404,11 +404,8 @@ export function handleConverseStreamContentBlockDelta(
       }),
     });
   } else {
-    const unsupportedField = Object.entries(contentBlockDelta.delta).filter(
-      ([_, value]) => !!value
-    );
     throw new Error(
-      `Unsupported content block type: ${unsupportedField[0][0]}`
+      `Unsupported content block type(s): ${JSON.stringify(contentBlockDelta.delta, null, 2)}`
     );
   }
 }

diff --git a/libs/langchain-aws/src/tests/chat_models.test.ts b/libs/langchain-aws/src/tests/chat_models.test.ts
@@ -3,8 +3,10 @@ import {
   HumanMessage,
   AIMessage,
   ToolMessage,
+  AIMessageChunk,
 } from "@langchain/core/messages";
-import { convertToConverseMessages } from "../common.js";
+import { convertToConverseMessages, handleConverseStreamContentBlockDelta } from "../common.js";
+import { concat } from "@langchain/core/utils/stream";
 
 test("convertToConverseMessages works", () => {
   const messages = [
@@ -71,3 +73,36 @@ test("convertToConverseMessages works", () => {
     url: "https://weather.com",
   });
 });
+
+test("Streaming supports empty string chunks", async () => {
+  const contentBlocks = [
+    {
+      contentBlockIndex: 0,
+      delta: {
+        text: "Hello ",
+      }
+    },
+    {
+      contentBlockIndex: 0,
+      delta: {
+        text: "",
+      }
+    },
+    {
+      contentBlockIndex: 0,
+      delta: {
+        text: "world!",
+      }
+    }
+  ]
+
+  let finalChunk: AIMessageChunk | undefined;
+  for (const block of contentBlocks) {
+    const chunk = handleConverseStreamContentBlockDelta(block).message;
+    finalChunk = !finalChunk ? chunk : concat(finalChunk, chunk);
+  }
+
+  expect(finalChunk).toBeDefined();
+  if (!finalChunk) return;
+  expect(finalChunk.content).toBe("Hello world!");
+})