fix: Don't crash when receiving non-string, non-array headers (#197)

Author: AaronMoat

.changeset/polite-trainers-camp.md

@@ -0,0 +1,5 @@
+---
+'@apollo/datasource-rest': patch
+---
+
+Don't crash when receiving non-string, non-array headers

src/HTTPCache.ts

@@ -331,12 +331,12 @@ function cachePolicyHeadersToNodeFetchHeadersInit(
 ): NodeFetchHeadersInit {
   const headerList = [];
   for (const [name, value] of Object.entries(headers)) {
-    if (typeof value === 'string') {
-      headerList.push([name, value]);
-    } else if (value) {
+    if (Array.isArray(value)) {
       for (const subValue of value) {
         headerList.push([name, subValue]);
       }
+    } else if (value) {
+      headerList.push([name, value]);
     }
   }
   return headerList;
@@ -354,10 +354,10 @@ function cachePolicyHeadersToFetcherHeadersInit(
 ): Record<string, string> {
   const headerRecord = Object.create(null);
   for (const [name, value] of Object.entries(headers)) {
-    if (typeof value === 'string') {
-      headerRecord[name] = value;
-    } else if (value) {
+    if (Array.isArray(value)) {
       headerRecord[name] = value.join(', ');
+    } else if (value) {
+      headerRecord[name] = value;
     }
   }
   return headerRecord;

src/__tests__/RESTDataSource.test.ts

@@ -1848,6 +1848,35 @@ describe('RESTDataSource', () => {
         await dataSource.getFoo(2, true);
       });
 
+      it('should not crash in revalidation flow header handling when sending non-array non-string headers', async () => {
+        jest.useFakeTimers({ doNotFake: ['nextTick'] });
+
+        const dataSource = new (class extends RESTDataSource {
+          override baseURL = apiUrl;
+
+          getFoo(id: number) {
+            return this.fetch(`foo/${id}`, {
+              headers: {
+                // @ts-expect-error
+                x: 1,
+              },
+              cacheOptions: { ttl: 1 },
+            });
+          }
+        })();
+
+        nock(apiUrl).get('/foo/1').times(2).reply(200);
+
+        await dataSource.getFoo(1);
+        await dataSource.getFoo(1);
+
+        jest.advanceTimersByTime(1000);
+
+        await dataSource.getFoo(1);
+
+        jest.useRealTimers();
+      });
+
       describe('raw header access when using node-fetch', () => {
         it('for a non-cacheable request', async () => {
           const dataSource = new (class extends RESTDataSource {