Inconsistent behaviors between the native `Deno.KV.list` method and the one of `@deno/kv` package

[AbdulrhmanGoni]

What's wrong?

I built a desktop client app to manage Deno KV databases.
I designed the app to work with both Deno.KV client and the Node implementation of Deno KV client
provided by the @deno/kv package, since both expose the same API and interact with the same database.

However, while developing and using the app, I noticed some inconsistent behaviors between the native Deno.KV.list() method (in Deno runtime) and the one of the @deno/kv package (in Node).

Behavior Differences

Here are three confusing and unexpected behaviors I encountered:

[1] Selector keys with undefined value

In Deno, when you pass selector keys with undefined value to Deno.KV.list method like the following:

const kv = await Deno.openKv();
const iterator = kv.list({ prefix: ["users"], end: undefined, start: undefined });
for await (const entry of iterator) {/*...*/}

This will work fine as you only specified prefix selector (ignoring end and start because they are undefined)

But when you do the same in Node with @deno/kv package and pass selector keys with undefined value to the kv.list method:

import { openKv } from "@deno/kv";
const kv = await openKv();
const iterator = kv.list({ prefix: ["users"], end: undefined, start: undefined });
for await (const entry of iterator) {/*...*/}

You get the following error:

TypeError: Selector can not specify both 'start' and 'end' keys when specifying 'prefix'

I looked at @deno/kv package's code. Apparently, this happens because the package uses the in operator to check keys existence regardless of the types of their values

[2] Invalid range key with prefix selector

When you pass an invalid range key ("end" or "start") with the prefix selector to Deno.KV.list method like the following:

const kv = await Deno.openKv();
const iterator = kv.list({ prefix: ["users"], end: ["C"] });
for await (const entry of iterator) {/*...*/}

The following error will be thrown (which is expected):

TypeError: End key is not in the keyspace defined by prefix

But passing the same invalid range key in Node to @deno/kv package's list method does not throw any error:

import { openKv } from "@deno/kv";
const kv = await openKv();
const iterator = kv.list({ prefix: ["users"], end: ["C"] });
for await (const entry of iterator) {/*...*/}

No error, even though the end key is outside the keyspace defined by the prefix.

[3] Incomplete selector keys

When passing an incomplete selector (e.g, passing only {start: [...]} or {end: [...]}, or an empty one {}) to the Deno.KV.list method like this:

const kv = await Deno.openKv();
const iterator = kv.list({ start: [10] }); // or `{ end: [10] }` or `{}`
for await (const entry of iterator) {/*...*/}

An error will be thrown (which is also expected):

TypeError: Selector must specify either 'prefix' or both 'start' and 'end' key

But in Node with @deno/kv package, passing an incomplete selector throws a completely different and confusing error:

import { openKv } from "@deno/kv";
const kv = await openKv();
const iterator = kv.list({ start: [10] }); // or `{ end: [10] }` or `{}`
for await (const entry of iterator) {/*...*/}

This error will be thrown:

TypeError: Cannot read properties of undefined (reading 'flatMap')