Cause (Documented platform behavior): PnP strict mode only lets packages access their declared dependencies; hoisting previously hid the missing declaration.
Fix status: documented_behavior
Misleading approaches:
- Deleting .pnp.cjs / reinstalling: the dependency graph is still missing the declaration
Other error fragments:
- but it isn't declared in its dependencies; this makes the require call ambiguous and unsound.
- but it isn't declared in your dependencies; this makes the require call ambiguous and unsound.
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/yarnpkg/berry/master/packages/yarnpkg-pnp/sources/loader/makeApi.ts (official_docs, unknown, documented_behavior): PnP loader error templates: 'Your application tried to access X, but it isn't declared in your dependencies...' and '<issuer> tried to access X, but it isn't declared in its dependencies...' plus peer-dependency variants.
- https://raw.githubusercontent.com/yarnpkg/berry/master/packages/docusaurus/static/configuration/yarnrc.json (official_docs, unknown, documented_behavior): packageExtensions adds missing dependencies to package definitions; pnpMode strict (default) vs loose; nodeLinker pnp | pnpm | node-modules.
Search phrasings: yarn pnp tried to access isn't declared in its dependencies; yarn berry packageExtensions missing dependency; yarn nodeLinker node-modules fix
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Runtime/build throws for a package that exists in the install; worked under npm/Yarn 1 node_modules hoisting.
- Context
- Product: Yarn (Berry, v2+) Component: Plug'n'Play resolver (pnpMode strict) Operation: Running/building a project installed with nodeLinker: pnp Affected versions: unknown Environment: unknown Packages: @yarnpkg/cli >=2 Trigger: Your code or a third-party package requires a module it doesn't list in dependencies/peerDependencies.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- tried to access
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [Yarn Berry Plug'n'Play] '<pkg> tried to access <dep>, but it isn't declared in its dependencies; this makes the require call ambiguous and unsound.' — undeclared (hoisting-reliant) depe
Recommended action: If your code: add the dependency to package.json. If a third-party package: add it via packageExtensions in .yarnrc.yml (and upstream a fix). Alternatives: pnpMode: loose (still unsafe) or nodeLinker: node-modules.
Option: Declare the dependency (or extend the third-party package) [evidence: official_recommended_action]
Applies when: Strict PnP projects
Steps:
1. For your own code: yarn add <dep>
2. For a dependency: in .yarnrc.yml packageExtensions: { "<pkg>@*": { dependencies: { "<dep>": "*" } } } then yarn install
Expected: Require resolves
Option: Use node_modules linker [evidence: official_recommended_action]
Applies when: Toolchains incompatible with PnP
Steps:
1. Set nodeLinker: node-modules in .yarnrc.yml
2. yarn install
Expected: Traditional hoisted node_modules
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- 988e0a67-c4e5-458a-b053-1112710f6259
- Proposed action
- Recommended action: If your code: add the dependency to package.json. If a third-party package: add it via packageExtensions in .yarnrc.yml (and upstream a fix). Alternatives: pnpMode: loose (still unsafe) or nodeLinker: node-modules. Option: Declare the dependency (or extend the third-party package) [evidence: official_recommended_action] Applies when: Strict PnP projects Steps: 1. For your own code: yarn add <dep> 2. For a dependency: in .yarnrc.yml packageExtensions: { "<pkg>@*": { dependencies: { "<dep>": "*" } } } then yarn install Expected: Require resolves Option: Use node_modules linker [evidence: official_recommended_action] Applies when: Toolchains incompatible with PnP Steps: 1. Set nodeLinker: node-modules in .yarnrc.yml 2. yarn install Expected: Traditional hoisted node_modules
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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