Testing yarn alias with Deep Dependencies

README.md

Testing yarn alias with Deep Dependencies

Yarn tip: You can alias a package by using yarn add fake-name@npm:left-pad. Now you can use require("fake-name") to require left-pad.

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This could be useful for module level dependency injection or inversion of control...

TLDR; This works for peerDependencies of your dependencies,

but not for dependencies of your dependencies. See test 3.

The Idea

So we'll try it with get-query-param which depends on query-string v5.0.0 which we will replace with qs.

The Setup

Create a new project with yarn init.

Test 1

1. yarn add query-string@npm:qs
2. yarn add get-query-param

Result: Failure

get-query-param got its own copy of query-string in node_modules/get-query-param/node_modules/query-string.

Test 2

1. yarn add query-string@npm:qs get-query-param

Result: Failure

get-query-param got its own copy of query-string in node_modules/get-query-param/node_modules/query-string.

Test 3 (with peerDependencies)

1. Clone get-query-param to ../get-query-param2, change the package name and move query-string from dependencies to peerDependencies in its package.json.
2. yarn add query-string@npm:qs
3. yarn add file:./../get-query-param2
4. copy test.js from node_modules/get-query-param2 to project root and modify its import, then run yarn add ava, add scripts: { test: 'ava -v'} to your own package.json and then run yarn test.

Result: Success!

get-query-param2 uses qs as its query-serializer and all tests pass.

Interesting. So the only way to fix this is by forking the packages that list the package you're trying to alias and moving it to peerDependencies?