Fixed functions that return null causing crashes (#31)

---------
Co-authored-by: Daniel Chambers <[email protected]>

Author: danieljharvey

CHANGELOG.md

@@ -12,6 +12,7 @@ Changes to be included in the next upcoming release
 - Support for NDC Spec v0.1.2 via the NDC TypeScript SDK v4.4.0 ([#29](https://github.com/hasura/ndc-nodejs-lambda/pull/29)).
   - Built-in scalar types that support equality now define it in the NDC schema.
   - Built-in scalar types now have an explicit type representation defined in the NDC schema.
+- Fixed functions that return null causing crashes ([#31](https://github.com/hasura/ndc-nodejs-lambda/pull/31))
 
 ## [1.2.0] - 2024-03-18
 - Improved error messages when unsupported enum types or unions of literal types are found, and allow these types to be used in relaxed types mode ([#17](https://github.com/hasura/ndc-nodejs-lambda/pull/17))

ndc-lambda-sdk/src/execution.ts

@@ -170,10 +170,10 @@ function coerceArgumentValue(value: unknown, type: schema.TypeReference, valuePa
 async function invokeFunction(func: Function, preparedArgs: unknown[], functionName: string): Promise<unknown> {
   try {
     return await withActiveSpan(tracer, `Function: ${functionName}`, async () => {
-      const result = func.apply(undefined, preparedArgs);
+      const result: unknown = func.apply(undefined, preparedArgs);
       // Await the result if it is a promise
-      if (typeof result === "object" && 'then' in result && typeof result.then === "function") {
-        return await result;
+      if (result !== null && typeof result === "object" && "then" in result && typeof result.then === "function") {
+        return await (result as PromiseLike<unknown>);
       }
       return result;
     }, { [FUNCTION_NAME_SPAN_ATTR_NAME]: functionName });

ndc-lambda-sdk/test/execution/execute-query.test.ts

@@ -2,7 +2,7 @@ import { describe, it } from "mocha";
 import { assert, expect } from "chai";
 import * as sdk from "@hasura/ndc-sdk-typescript"
 import { executeQuery } from "../../src/execution";
-import { FunctionNdcKind, FunctionsSchema } from "../../src/schema";
+import { FunctionNdcKind, FunctionsSchema, NullOrUndefinability } from "../../src/schema";
 import { sleep } from "../../src/util";
 
 describe("execute query", function() {
@@ -389,9 +389,13 @@ describe("execute query", function() {
           parallelDegree: null,
           arguments: [],
           resultType: {
-            type: "named",
-            kind: "scalar",
-            name: "String"
+            type: "nullable",
+            nullOrUndefinability: NullOrUndefinability.AcceptsNullOnly,
+            underlyingType: {
+              type: "named",
+              kind: "scalar",
+              name: "String"
+            }
           }
         }
       },
@@ -493,5 +497,77 @@ describe("execute query", function() {
       ]);
       assert.equal(functionCallCount, 1);
     });
+
+    it("function can return null", async function() {
+      let functionCallCount = 0;
+      const runtimeFunctions = {
+        "theFunction": () => {
+          functionCallCount++;
+          return null;
+        }
+      };
+      const queryRequest: sdk.QueryRequest = {
+        collection: "theFunction",
+        query: {
+          fields: {
+            "__value": {
+              type: "column",
+              column: "__value"
+            }
+          }
+        },
+        arguments: {},
+        collection_relationships: {}
+      };
+
+      const result = await executeQuery(queryRequest, functionSchema, runtimeFunctions);
+      assert.deepStrictEqual(result, [
+        {
+          aggregates: null,
+          rows: [
+            {
+              "__value": null,
+            }
+          ]
+        }
+      ]);
+      assert.equal(functionCallCount, 1);
+    });
+
+    it("async function can return null", async function() {
+      let functionCallCount = 0;
+      const runtimeFunctions = {
+        "theFunction": async () => {
+          functionCallCount++;
+          return null;
+        }
+      };
+      const queryRequest: sdk.QueryRequest = {
+        collection: "theFunction",
+        query: {
+          fields: {
+            "__value": {
+              type: "column",
+              column: "__value"
+            }
+          }
+        },
+        arguments: {},
+        collection_relationships: {}
+      };
+
+      const result = await executeQuery(queryRequest, functionSchema, runtimeFunctions);
+      assert.deepStrictEqual(result, [
+        {
+          aggregates: null,
+          rows: [
+            {
+              "__value": null,
+            }
+          ]
+        }
+      ]);
+      assert.equal(functionCallCount, 1);
+    });
   });
 });