peerDependency hell about ajv-draft-04

[rolfl]

With NPM version 7.x it appears the new peerDependency handling (force-loading peerDependencies instead of ignoring them) changes the behaviour see: https://github.blog/2021-02-02-npm-7-is-now-generally-available/#peer-dependencies :

│ └─┬ [email protected]
│   ├─┬ @seriousme/[email protected]
│   │ ├─┬ [email protected]
│   │ │ └── [email protected] deduped
│   │ └── [email protected]
│   ├─┬ [email protected]
│   │ └── [email protected]
│   └── [email protected]
├─┬ [email protected]
│ ├─┬ @eslint/[email protected]
│ │ └── [email protected]
│ ├── [email protected]
│ └─┬ [email protected]
│   └── [email protected]
└─┬ [email protected]
  ├─┬ @fastify/[email protected]
  │ └── [email protected]
  ├─┬ [email protected]
  │ └── [email protected]
  └─┬ [email protected]
    └── [email protected]

Humph... closing this, but pleased to have recorded this so maybe someone else can be saved a few hours of debugging.

Note that npm 7 with --legacy-peer-deps option does things differently again, the install runs CLEAN (NO ERRORS OR WARNINGS), but npm ls ajv shows:

│ └─┬ [email protected]
│   ├─┬ @seriousme/[email protected]
│   │ ├─┬ [email protected]
│   │ │ └── [email protected] deduped invalid: "^8.5.0" from node_modules/ajv-draft-04
│   │ └── [email protected]
│   ├─┬ [email protected]
│   │ └── [email protected]
│   └── [email protected]

Running the application fails with:

/home/rolf/bmix/myapp/node_modules/ajv-draft-04/dist/vocabulary/draft4.js:11
    applicator_1.default(),
                        ^

TypeError: applicator_1.default is not a function
    at Object.<anonymous> (/home/rolf/bmix/myapp/node_modules/ajv-draft-04/dist/vocabulary/draft4.js:11:25)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
    at Module.load (internal/modules/cjs/loader.js:928:32)