fix: don't crash serializing an explicit null/undefined param value

src/serialize.test.ts

@@ -76,6 +76,27 @@ test("serializer should not mutate params", () => {
   expect(params.location).toBe(location);
 });
 
+test("serializer should not format an explicit null/undefined value, and should drop it from the query string", () => {
+  expect(
+    serializer(
+      { location: latLngToString },
+      "http://mock.url"
+    )({
+      radius: 50000,
+      location: undefined,
+    })
+  ).toBe("radius=50000");
+  expect(
+    serializer(
+      { location: latLngToString },
+      "http://mock.url"
+    )({
+      radius: 50000,
+      location: null,
+    })
+  ).toBe("radius=50000");
+});
+
 test("serializer should return pipe joined arrays by default", () => {
   expect(serializer({}, "http://mock.url")({ foo: ["b", "a", "r"] })).toBe(
     "foo=b|a|r"

src/serialize.ts

@@ -125,7 +125,17 @@ export function serializer(
 
     for (const key of Object.keys(format)) {
       if (key in serializedParams) {
-        serializedParams[key] = format[key](serializedParams[key]);
+        // An explicit `null`/`undefined` (e.g. `{ location: undefined }`) means
+        // "not supplied", not "format this value" — several format functions
+        // (e.g. `latLngToString`) throw on it. Deleting the key rather than
+        // leaving it as-is also sidesteps `qs()`'s inconsistent handling of
+        // the two: it drops `undefined` from the query string by default but
+        // keeps `null` as a bare, value-less key.
+        if (serializedParams[key] == null) {
+          delete serializedParams[key];
+        } else {
+          serializedParams[key] = format[key](serializedParams[key]);
+        }
       }
     }