Node 10 isn't supported anymore.
Plugins can't access yup anymore (we migrated to Typanion as part of Clipanion v3).
- To upgrade workspace-tools, remove it from your .yarnrc.yml, upgrade, then import it back.
The enableImmutableInstalls will now default to true on CI (we still recommend to explicitly use --immutable on the CLI).
- You can re-allow mutations by adding YARN_ENABLE_IMMUTABLE_INSTALLS=false in your environment variables.
The initVersion and initLicense configuration options have been removed. initFields should be used instead.
Yarn will now generate .pnp.cjs files (instead of .pnp.js) when using PnP, regardless of what the type field inside the manifest is set to.
The virtual folder (used to disambiguate peer dependencies) got renamed from $$virtual into __virtual__.
The -a alias flag of yarn workspaces foreach got removed; use -A,--all instead, which is strictly the same.
The old PnPify SDK folder (.vscode/pnpify) won't be cleaned up anymore.
The --skip-builds flag from yarn install got renamed into --mode=skip-build.
The bstatePath configuration option has been removed. The build state (.yarn/build-state.yml) has been moved into the install state (.yarn/install-state.gz)
The cache files need to be regenerated. We had to change their timestamps in order to account for a flaw in the zip spec that was causing problems with some third-party tools.
@yarnpkg/pnpify has been refactored into 3 packages:
- @yarnpkg/sdks now contains the Editor SDKs
- @yarnpkg/pnpify now contains the PnPify CLI compatibility tool that creates in-memory node_modules
- @yarnpkg/nm now contains the node_modules tree builder and hoister
@yarnpkg/plugin-node-modules has been renamed to @yarnpkg/plugin-nm
The --clipanion=definitions commands supported by our CLIs will now expose the definitions on the entry point (rather than on .command)

API

structUtils.requirableIdent got removed; use structUtils.stringifyIdent instead, which is strictly the same.
configuration.format got removed; use formatUtils.pretty instead, which is strictly the same, but type-safe.
httpUtils.Options['json'] got removed; use httpUtils.Options['jsonResponse'] instead, which is strictly the same.
PackageExtension['description'] got removed, use formatUtils.json(packageExtension, formatUtils.Type.PACKAGE_EXTENSION) instead, which is strictly the same.
Project.generateBuildStateFile has been removed, the build state is now in Project.storedBuildState.
Project.tryWorkspaceByDescriptor and Project.getWorkspaceByDescriptor now match on virtual descriptors.

Installs

Workspaces now get self-references even when under the node-modules linker (just like how it already worked with the pnp linker). This means that a workspace called foo can now safely assume that calls to require('foo/package.json') will always work, removing the need for absolute aliases in the majority of cases.
The node-modules linker now does its best to support the portal: protocol. This support comes with two important limitations:
- Projects that make use of such dependencies will have to be run with the --preserve-symlinks Node option if they wish to access their dependencies.
- Because Yarn installs will never modify files outside of the project due to security reasons, sub-dependencies of packages with portal: must be hoisted outside of the portal. Failing that (for example if the portal package depends on something incompatible with the version hoisted via another package), the linker will produce an error and abandon the install.
The node-modules linker can now utilize hardlinks. The new setting nmMode: classic | hardlinks-local | hardlinks-global specifies which node_modules strategy should be used:
- classic - standard node_modules layout, without hardlinks
- hardlinks-local - standard node_modules layout with hardlinks inside the project only
- hardlinks-global - standard node_modules layout with hardlinks pointing to global content storage across all the projects using this option

Bugfixes

Yarn now has a proper governance model.
The node-modules linker will now ensure that the generated install layouts are terminal, by doing several rounds when needed.
The node-modules linker will no longer print warnings about postinstall scripts when a workspace depends on another workspace listing install scripts.
Peer dependencies depending on their own parent are now properly hoisted by the node-modules linker.
Boolean values will be properly interpreted when specified inside the configuration file via the ${ENV_VAR} syntax.
Should any of preinstall, install, postinstall fail, the remaining scripts will be skipped.
The git: protocol will now default to fetching HEAD (rather than the hardcoded master).
The SIGTERM signal will now be propagated to child processes.
The PnP linker now schedules packages to be rebuilt if their unplugged folder is removed
yarn config unset will now correctly unset non-nested properties
The TypeScript SDK now
And a bunch of smaller fixes.

Settings

Various initFields edge cases have been fixed.
The preferAggregateCacheInfo flag will now also aggregate cleanup reports.
A new enableMessageNames flag can be set to false to exclude the YNxxxx from the output.

Commands

yarn init can now be run even from within existing projects (will create missing files).
yarn init and yarn set version will set the packageManager field.
yarn set version now downloads binaries from the official Yarn website (rather than GitHub).
yarn set version from sources will now upgrade the builtin plugins as well unless --skip-plugins is set.
yarn version apply now supports a new --prerelease flag which replaces how prereleases were previously handled.
yarn run should be significantly faster to boot on large projects.
yarn workspaces foreach --verbose will now print when processes start and end, even if they don't have an output.
yarn workspaces foreach now supports a --from <glob> flag, which when combined with -R will target workspaces reachable from the 'from' glob.
yarn patch-commit can now be used as many times as you want on the same patch folder.
yarn patch-commit now supports a new -s,--save flag which will save the patch instead of just printing it.
yarn up now supports a new -R,--recursive flag which will upgrade the specified package, regardless where it is.
yarn config unset is a new command that will remove a setting from the local configuration (or home if -H is set).
yarn exec got support for running shell scripts using Yarn's portable shell.
yarn plugin import can now install specific versions of the official plugins.
yarn plugin import will now download plugins compatible with the current CLI by default.
yarn unlink has been added which removes resolutions previously set by yarn link.

Builtin Shell

The shell now supports background jobs, with color-coded output.
It now also supports redirections from file descriptors.

Compatibility

Running yarn install inside a Yarn v1 project will now automatically enable the node-modules linker. This should solve most of the problems people have had in their migrations. We still recommend to keep the default PnP for new projects, but the choice is yours.
The patched filesystem now supports file URLs, bigint, and fstat.
An official ESBuild resolver is now provided under the name @yarnpkg/esbuild-plugin-pnp. We use it to bundle Yarn itself!
PnP projects can now use the Node exports field - regardless of the Node version.
The PnP hook now supports the node: protocol (new in Node 16)
The Prettier SDK does not use PnPify anymore since it was its only remaining use, and was fairly invasive; as a result, the Prettier plugins must be specified in Prettier's plugins configuration property.
Zip terminal links can now be clicked from within VSCode
Builtin patches that fail to apply will no longer cause an error (they'll emit a warning and the original sources will be used instead).
- Remember that patches are a problem for our team too, and that we only do this because we don't have any other option available to us right now - if you wish to help, consider upvoting the relevant pull request in the TypeScript repository or, if you work at Microsoft, perhaps mention to your TypeScript team next door that fixing this would benefit you.