Yarn warns about unmet peer dependencies

[fson]

Description

When running create-react-app 0.7.0 with Yarn installed, Yarn prints a warning about unmet peer dependencies. However, despite the warning the app is created successfully, it works and subsequent yarn install commands don't show this warning.

Expected behavior

No warnings about peer dependencies should be printed when running create-react-app.

Actual behavior

Following warnings are printed:

> create-react-app my-app-yarn
Creating a new React app in /Users/ville/Projects/sandbox/my-app-yarn.

Installing packages. This might take a couple minutes.
Installing react-scripts...

yarn add v0.17.10
info No lockfile found.
[1/4] 🔍  Resolving packages...
warning react-scripts > jest > jest-cli > istanbul-api > fileset > minimatch@2.0.10: Please update to minimatch 3.0.2 or higher to avoid a RegExp DoS issue
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning Unmet peer dependency "eslint@>=1.6.0 <4.0.0".
warning Unmet peer dependency "babel-core@^6.0.0".
warning Unmet peer dependency "webpack@1 || ^2.1.0-beta".
warning Unmet peer dependency "babel-eslint@7.0.0".
warning Unmet peer dependency "eslint@3.8.1".
warning Unmet peer dependency "eslint-plugin-flowtype@2.21.0".
warning Unmet peer dependency "eslint-plugin-import@2.0.1".
warning Unmet peer dependency "eslint-plugin-jsx-a11y@2.2.3".
warning Unmet peer dependency "eslint-plugin-react@6.4.1".
warning Unmet peer dependency "eslint@>=2.0.0".
warning Unmet peer dependency "webpack@^1.9.11".
warning Unmet peer dependency "eslint@^2.10.2 || 3.x".
warning Unmet peer dependency "webpack@1 || ^2.1.0-beta".
warning Unmet peer dependency "eslint@2.x - 3.x".
warning Unmet peer dependency "eslint@^2.0.0 || ^3.0.0".
warning Unmet peer dependency "file-loader@*".
warning Unmet peer dependency "webpack@>=1.3.0 <3".
warning Unmet peer dependency "webpack@1 || ^2.1.0-beta".
[4/4] 📃  Building fresh packages...
success Saved lockfile.
success Saved 750 new dependencies.
...

Environment

> node -v
v6.9.1
> npm -v
3.10.8
> yarn --version
0.17.10

Operating system: macOS 10.12.1
Browser and version: N/A

[gaearon]

Also this on the second stage:

yarn add v0.17.6
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning Unmet peer dependency "react@^15.4.1".

[fson]

Looks like a bug in Yarn – it doesn't consider the packages installed at the same time when looking for peer dependencies. I tried this (without using create-react-app):

> mkdir test
> cd test
> yarn init -y
...
> yarn add react react-dom
yarn add v0.17.10
info No lockfile found.
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning Unmet peer dependency "react@^15.4.1".

[fson]

I created an issue in Yarn: yarnpkg/yarn#2132

[gaearon]

I guess I'll close since this is a known issue in Yarn, and keeping it open here doesn't change anything. We still track it in the umbrella task. #1189