fix: avoid undefined metadata when retrieval finds no context

src/context-service/index.ts

@@ -104,7 +104,8 @@ export class ContextService {
               run_type: "tool",
             }
           )(context),
-          metadata: context.map(({ metadata }) => metadata) as TMetadata[],
+          metadata:
+            context.length > 0 ? context.map(({ metadata }) => (metadata ?? {}) as TMetadata) : [],
           rawContext: context,
         };
       },

src/database.retrieve.test.ts

@@ -0,0 +1,63 @@
+import { describe, expect, mock, test } from "bun:test";
+import { Database } from "./database";
+
+describe("Database.retrieve — empty / missing metadata (#49)", () => {
+  test("returns [] when every result has undefined data", async () => {
+    const query = mock(() =>
+      Promise.resolve([
+        { id: "1", score: 0.9, data: undefined, metadata: undefined },
+        { id: "2", score: 0.8, data: undefined, metadata: undefined },
+        { id: "3", score: 0.7, data: undefined, metadata: undefined },
+        { id: "4", score: 0.6, data: undefined, metadata: undefined },
+        { id: "5", score: 0.5, data: undefined, metadata: undefined },
+      ])
+    );
+
+    const database = new Database({ query } as never);
+    const result = await database.retrieve({
+      question: "unrelated question",
+      topK: 5,
+      similarityThreshold: 0.5,
+      namespace: "",
+    });
+
+    expect(result).toEqual([]);
+    expect(query).toHaveBeenCalled();
+  });
+
+  test("returns [] when the vector index yields no rows", async () => {
+    const query = mock(() => Promise.resolve([]));
+    const database = new Database({ query } as never);
+
+    const result = await database.retrieve({
+      question: "anything",
+      topK: 5,
+      similarityThreshold: 0.5,
+      namespace: "",
+    });
+
+    expect(result).toEqual([]);
+  });
+
+  test("coerces missing metadata to {} instead of undefined", async () => {
+    const query = mock(() =>
+      Promise.resolve([
+        { id: "1", score: 0.95, data: "Tokyo is the capital of Japan.", metadata: undefined },
+        { id: "2", score: 0.9, data: "Kyoto was the former capital.", metadata: { unit: "A" } },
+      ])
+    );
+
+    const database = new Database({ query } as never);
+    const result = await database.retrieve<{ unit?: string }>({
+      question: "capital of Japan",
+      topK: 5,
+      similarityThreshold: 0.5,
+      namespace: "",
+    });
+
+    expect(result.map(({ id, metadata }) => ({ id, metadata }))).toEqual([
+      { id: "1", metadata: {} },
+      { id: "2", metadata: { unit: "A" } },
+    ]);
+  });
+});

src/database.ts

@@ -127,22 +127,19 @@ export class Database {
 
     if (allValuesUndefined) {
       console.error("There is no answer for this question in the provided context.");
-
-      return [
-        {
-          data: "There is no answer for this question in the provided context.",
-          id: "error",
-          metadata: {} as TMetadata,
-        },
-      ];
+      // Return an empty list so callers do not surface a fixed-size array of
+      // undefined metadata (default topK is 5) when nothing relevant is found.
+      return [];
     }
 
     const facts = result
       .filter((x) => x.score >= similarityThreshold)
       .map((embedding) => ({
         data: embedding.data ?? "",
         id: embedding.id.toString(),
-        metadata: embedding.metadata as TMetadata,
+        // Vectors without stored metadata previously leaked `undefined` entries
+        // into `chat()` responses (see #49).
+        metadata: (embedding.metadata ?? {}) as TMetadata,
       }));
 
     return facts;