feat: add cluster.duplicate() method

[SGrondin]

Hi,

See #921. This PR adds the missing cluster.duplicate() method.

Notes:

• I'm using this.startupNodes.slice(0) to ensure we pass a copy and not a reference. This matches the behavior of the options, which also get a copy thanks to Object.assign().
• I'm not sure this new test I added is being executed when running npm test. I don't see it in the mocha output. It works as expected when I run npx mocha test/functional/cluster/duplicate.ts, could someone please validate?

[luin]

LGTM. The test should be executed since npm test simply calls mocha test/**/*.ts. "test/functional/cluster/duplicate.ts" matches the pattern. Does npx mocha test/**/*.ts execute the test?

[SGrondin]

Wow, that's a quick response!

Unfortunately npx mocha test/**/*.ts fails to run any tests because of a compilation error in test/functional/scan_stream.ts. I'm guessing it's also why npm test isn't running the new test.

TSError: ⨯ Unable to compile TypeScript:
test/functional/scan_stream.ts:239:15 - error TS2339: Property 'sadd' does not exist on type 'Cluster'.
test/functional/scan_stream.ts:240:30 - error TS2339: Property 'sscanStream' does not exist on type 'Cluster'.

[luin]

I see. There are some issues related to type which will be fixed in the next major version. Just pushed a temp fix. Please merge the latest commit and try again.

[SGrondin]

I've rebased on top of the latest commit and fixed the code formatting issues. The build is passing but I still don't see the new test. It should be under a describe grouped called #duplicate. All I see is the other duplicate test, for the base client.

[luin]

It seems that mocha ignores tests that contain TypeScript errors, which is the reason the newly added test wasn't executed, as well as some other tests. Didn't notice this issue before.

[luin]

@SGrondin Just did some fixes for the issues. Merge the latest commits will do the trick.

[SGrondin]

Very nice. It ran 55 tests that were previously ignored.

[ioredis-robot]

🎉 This PR is included in version 4.12.0 🎉

The release is available on:

• npm package (@next dist-tag)
• GitHub release

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