Added dedupe option to prevent bundling the same package multiple times

[sormy]

Added dedupe option to prevent bundling the same package multiple times with unit tests

Very useful feature to make sure that specific dependency will be bundled only once and root node_modules version will be used. When npm link is used with a lot of packages it could cause specific package version to be in each package's node_modules and bundling for this scenario will cause that multiple versions of the same package will be bundled even if it is exactly the same version. Usually this is solved by defining package as peer dependency but this package could be also included in devDependencies for tests and this causes it to appear under node_modules.

[sormy]

The test is failing on "allows custom options" for NodeJS v6.x only.

[sormy]

I can confirm that regression for this failing test on node 6.x was introduced in commit 1eff8d7, most likely caused by package-lock.json update.

My change is good and don't break any tests, safe to merge.

I can add something like below to skip this test on node v6.x but it is completely unrelated to my change:

	it( 'allows custom options', () => {
		// node v6.x support for this feature was broken in 1eff8d75eaa914ff7ffc1663f9b34826e1c8f71d
		if (/^6./.test(process.versions.node)) {
			return;
		}
                 ...
        }

[sormy]

Hi, any update?

[lukastaegert]

Thanks, looks good to me! Could you please merge in latest master and add the new option to the index.d.ts typings as well? This should also solve the test issues.

[sormy]

done

[philipwalton]

Shouldn't the dedupe option default to deduping everything, and then you can provide exceptions if you know you want more than one version of a particular package?

As it is now, a user would have to first discover that duplication was occurring and then proactively use this option to fix it. Discovering duplication in a bundle isn't easy, so by not having it be the default, I think this will solve very few people's problems.