[Bug?]: TypeScript 7 RC fails to install because the legacy TypeScript compat patch targets removed JS compiler files

[hamidrezahanafi]

Self-service

• I'd be willing to implement a fix

Describe the bug

Summary

Installing typescript@7.0.1-rc with Yarn fails because the built-in TypeScript compatibility patch is still applied to TypeScript 7. The patch was designed for the legacy JS compiler package layout and includes hunks for files such as lib/_tsc.js, which no longer exist in the TypeScript 7 native compiler package.
This should be addressed by: microsoft/typescript-go#1966

Fix PR limiting the patch to < 7 : #7190

To reproduce

Reproduction

yarn add typescript@7.0.1-rc

### Environment

```shell
System:
    OS: macOS 26.5.1
    CPU: (14) arm64 Apple M4 Pro
  Binaries:
    Node: 24.15.0 - /private/var/folders/c0/g9kchlzs17l77g7jpxkyrrh40000gp/T/xfs-89a14381/node
    Yarn: 4.15.0 - /private/var/folders/c0/g9kchlzs17l77g7jpxkyrrh40000gp/T/xfs-89a14381/yarn
    npm: 11.12.1 - /Users/hamidrezahanafi/.nvm/versions/node/v24.15.0/bin/npm
    bun: 1.3.4 - /Users/hamidrezahanafi/.bun/bin/bun
  npmPackages:
    jest: ^30.3.0 => 30.3.0

Additional context

Actual Behavior

Yarn attempts to apply the legacy TypeScript compat patch:

typescript@patch:typescript@npm%3A7.0.1-rc#optional!builtin<compat/typescript>

and fails with:

ENOENT: no such file or directory, lstat '/node_modules/typescript/lib/_tsc.js'

Expected Behavior

Yarn should not apply the legacy JS TypeScript compat patch to TypeScript 7, since TypeScript 7 uses the new native compiler package layout.

[wojtekmaj]

Temporary workaround that unblocked us on a nodeLinker: node-modules setup.

Since we don't use PnP, we don't need the TypeScript compat patch semantically; we only needed to prevent Yarn from rewriting the typescript descriptor to patch:...builtin<compat/typescript>, because the TS 7 RC package no longer has the JS compiler files that the legacy patch expects.

We added this local plugin:

// .yarn/plugins/plugin-disable-typescript-compat.cjs
module.exports = {
  name: "plugin-disable-typescript-compat",
  factory: (require) => {
    const { structUtils } = require("@yarnpkg/core");

    return {
      hooks: {
        reduceDependency: async (dependency) => {
          if (structUtils.stringifyIdent(dependency) !== "typescript")
            return dependency;

          if (!dependency.range.startsWith("patch:"))
            return dependency;

          const source = dependency.range.match(/^patch:([^#]+)/)?.[1];

          if (!source)
            return dependency;

          return {
            ...dependency,
            range: structUtils.parseDescriptor(decodeURIComponent(source)).range,
          };
        },
      },
    };
  },
};

And registered it before other plugins:

plugins:
  - path: .yarn/plugins/plugin-disable-typescript-compat.cjs
    spec: "plugin-disable-typescript-compat"

After that, yarn up typescript@rc resolved to plain typescript@npm:7.0.1-rc and installs/checks worked again. This is definitely a workaround rather than a fix, but it may be useful for other node-modules projects that don't rely on Yarn's PnP TypeScript patch.

[hamidrezahanafi]

Thanks @wojtekmaj for the workaround, I think my PR #7190 limiting the patch version should also be safe to land and unblock nodeLinker: node-modules fleet.

[wojtekmaj]

And your solution is undeniably better! Except for one detail: it needs to be released. I'm too eager to try the RC out to wait 😁

[maik-bol]

Amazing, thanks for this workaround. I'd solved it by patching the compat package to add the missing files as re-export stubs, but disabling the patch via a plugin is much cleaner, so I've switched to it.

I'll follow this thread until @hamidrezahanafi's PR (#7190) lands, since gating the builtin patch is the cleanest proper fix.

One caveat though: as written it bounds the patch to TS < 7, which fixes installing typescript@7.x directly but not the recommended TS6/TS7 side-by-side setup, where typescript is aliased to @typescript/typescript6 (a 6.x shim that is still < 7 and lacks the patched files, so it keeps failing).

I left a remark on the PR with a repro and two options to cover that case too. @hamidrezahanafi would you be open to extending it?

[abhi-airspace-intelligence]

Temporary workaround that unblocked us on a nodeLinker: node-modules setup.

Since we don't use PnP, we don't need the TypeScript compat patch semantically; we only needed to prevent Yarn from rewriting the typescript descriptor to patch:...builtin<compat/typescript>, because the TS 7 RC package no longer has the JS compiler files that the legacy patch expects.

We added this local plugin:

// .yarn/plugins/plugin-disable-typescript-compat.cjs
module.exports = {
name: "plugin-disable-typescript-compat",
factory: (require) => {
const { structUtils } = require("@yarnpkg/core");

return {
  hooks: {
    reduceDependency: async (dependency) => {
      if (structUtils.stringifyIdent(dependency) !== "typescript")
        return dependency;

      if (!dependency.range.startsWith("patch:"))
        return dependency;

      const source = dependency.range.match(/^patch:([^#]+)/)?.[1];

      if (!source)
        return dependency;

      return {
        ...dependency,
        range: structUtils.parseDescriptor(decodeURIComponent(source)).range,
      };
    },
  },
};

},
};
And registered it before other plugins:

plugins:

• path: .yarn/plugins/plugin-disable-typescript-compat.cjs
  spec: "plugin-disable-typescript-compat"
  After that, yarn up typescript@rc resolved to plain typescript@npm:7.0.1-rc and installs/checks worked again. This is definitely a workaround rather than a fix, but it may be useful for other node-modules projects that don't rely on Yarn's PnP TypeScript patch.

Note this is subtly wrong if you rely on immutable installs in your CI: this is what fixed it for me:

module.exports = {
  name: 'plugin-disable-typescript-compat',
  factory: require => {
    const { structUtils } = require('@yarnpkg/core');

    return {
      hooks: {
        reduceDependency: async dependency => {
          if (structUtils.stringifyIdent(dependency) !== 'typescript') return dependency;

          if (!dependency.range.startsWith('patch:')) return dependency;

          const source = dependency.range.match(/^patch:([^#]+)/)?.[1];

          if (!source) return dependency;

          const unpatched = structUtils.parseDescriptor(decodeURIComponent(source));

          return structUtils.makeDescriptor(dependency, unpatched.range);
        },
      },
    };
  },
};

[maik-bol]

We do rely on immutable installs, but everything seemed right, thanks for this but what does it exactly subtly fix?