yarnpkg/yarn

[feature] improve resolution deduping

Open

#3778 opened on Jun 30, 2017

View on GitHub
 (22 comments) (31 reactions) (0 assignees)JavaScript (41,514 stars) (2,731 forks)batch import
cat-featuregood first issuehelp wantedhigh-prioritytriaged

Description

Do you want to request a feature or report a bug? feature

Tentative about making it into 1.0 release because I think it is an important improvement over the existing experience.

What is the current behavior?

  1. Final deduping

As described in https://github.com/yarnpkg/yarn/issues/3775 whether Yarn will download 2 different versions of left-pad depends on the order dependencies are resolved (it's alphabetic BFS).

Instead we should have a post resolution step that would try to dedupe all versions of a single package to the minimum after the dependency tree was resolved.

I started this https://github.com/yarnpkg/yarn/pull/3563/files#diff-80a032b8112ef9aa0ea41ee304a6024aR453 but never have finished.

  1. Turn off deduping

At the same time we probably could have the opposite option - force Yarn to use latest dependencies everywhere and not optimize resolution at all.

  1. Don't dedupe lockfiles on install

Another aspect - we don't want to dedupe dependencies if they are already in the lockfile because Yarn guarantees same node_modules for the same lockfile.

Please mention your node.js, yarn and operating system version. Yarn 0.27

Contributor guide

Tech stack
javascriptnodejs
Domain
toolingdeveloper experiencecli
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Understanding of Yarn's dependency resolutionFamiliarity with Node.js and npmKnowledge of lockfile structureExperience with Yarn's codebase (optional)
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Review the linked PR #3563 for previous work on final deduping. Examine the resolution algorithm in the Yarn codebase, particularly the file referenced in the diff. Investigate the discussion in issue #3775 for context. Analyze the three sub features and design a cohesive implementation plan.