fix: Removes null and undefined values from top level payload

The EJSON.stringify library does not remove null and undefined values,
resulting in payloads that can contain sort, projection, etc set to
an explicit undefined. EJSON turns these into "null" and then MongoDB
cannot take the default value. The fix for this is to explicitly drop
any null or undefined values, but only at the top level, as updates
and aggregation pipelines need access to proper EJSON serialization.

Fixes #1

Author: thecodedrift

README.md

@@ -300,8 +300,8 @@ Requests via `fetch()` have their resposne codes checked against the [Data API E
 
 # FAQ
 
-- **Why is `mongodb` in the dependencies?** The short answer is [TypeScript requires it](https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#dependencies). The mongodb dependency is types-only and will not be included in your built lambda when using `tsc`, `rollup`, `webpack`, and other bundling tools. Unfortunately, to re-export the types, it must be included as a regular dependency instead of dev-dependency. You can verify that mongo is not included by looking at the [CommonJS build](https://www.npmjs.com/package/@taskless/mongo-data-api?activeTab=code).
-- **Why is `node-fetch`'s `fetch` not of the correct type?** The short answer is that `node-fetch`'s `fetch` isn't a true `fetch`. To work around this, you can either use [`cross-fetch`](https://github.com/lquixada/cross-fetch) which types the `fetch` API through a type assertion, or [perform the type assertion yourself](https://github.com/lquixada/cross-fetch/blob/main/index.d.ts): `fetch: _fetch as typeof fetch`. It's not ideal, but with proper `fetch` coming to node.js, it's a small inconvienence in the short term.
+- **Why is `mongodb` in the dependencies?** [TypeScript requires it](https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#dependencies), however, the mongodb dependency is types-only and will not be included in your built lambda when using `tsc`, `rollup`, `webpack`, etc. You can verify that mongo is not included by looking at the [CommonJS build](https://www.npmjs.com/package/@taskless/mongo-data-api?activeTab=code).
+- **Why is `node-fetch`'s `fetch` not of the correct type?** `node-fetch`'s `fetch` isn't a true `fetch` and wasn't typed as one. To work around this, you can either use [`cross-fetch`](https://github.com/lquixada/cross-fetch) which types the `fetch` API through a type assertion, or [perform the type assertion yourself](https://github.com/lquixada/cross-fetch/blob/main/index.d.ts): `fetch: _fetch as typeof fetch`. It's not ideal, but with proper `fetch` coming to node.js, it's a small inconvienence in the short term.
 
 # License
 

src/client.ts

@@ -66,6 +66,15 @@ export type MongoClientConstructorOptions = {
   headers?: OutgoingHttpHeaders | Headers;
 };
 
+/**
+ * Removes empty keys from an object at the top level. EJSON.stringify does not drop
+ * undefined values in serialization, so we need to explicitly remove any keys with
+ * null/undefined without recursing further into the object.
+ */
+const removeEmptyKeys = (object: Record<string, unknown>) => {
+  return Object.fromEntries(Object.entries(object).filter(([_, v]) => v));
+};
+
 /**
  * Create a MongoDB-like client for communicating with the Atlas Data API
  *
@@ -433,7 +442,7 @@ export class Collection<TSchema = Document> {
         collection: this.name,
         database: this.database.name,
         dataSource,
-        ...body,
+        ...removeEmptyKeys(body),
       }),
     });
 

test/mocks/handlers.ts

@@ -117,6 +117,19 @@ function first<T>(value: T | T[] | readonly T[]) {
   return asArray(value)[0];
 }
 
+const cannotBeNull: Record<string, string[]> = {
+  find: ["filter", "projection"],
+  findOne: ["filter", "projection", "sort", "limit", "skip"],
+  insertOne: [],
+  insertMany: [],
+  updateOne: ["upsert"],
+  updateMany: ["upsert"],
+  replaceOne: ["upsert"],
+  deleteOne: [],
+  deleteMany: [],
+  aggregate: [],
+};
+
 export const handlers = [
   rest.post(`${BASE_URL}/action/:action`, async (request, response, ctx) => {
     const body: {
@@ -158,6 +171,15 @@ export const handlers = [
       );
     }
 
+    // attempting to pass "null" for an optional top level field results in a 400 from mongo
+    const nonNullables =
+      cannotBeNull[request.params.action as keyof typeof cannotBeNull] ?? [];
+    for (const key of nonNullables) {
+      if (body[key] === null) {
+        return response(ctx.status(400), ctx.json({ error: "Bad Request" }));
+      }
+    }
+
     // find payload for use case
     const action = first(request.params?.action) ?? "";
     const conditions = payloads[action];