Should @types packages be dependencies or devDependencies?

[trusktr]

This isn't a bug or feature request, but I noticed that there are @types/ packages in the dependencies section of @material-ui/core. Shouldn't they be devDependencies instead? Or is there a reason for them to be dependencies?

Just wondering, because they current cause some errors in my app:

> tsc -p ./tsconfig.json --noEmit

node_modules/@types/react-transition-group/node_modules/@types/react/index.d.ts:2746:14 - error TS2300: Duplicate identifier 'LibraryManagedAttributes'.

2746         type LibraryManagedAttributes<C, P> = C extends React.MemoExoticComponent<infer T> | React.LazyExoticComponent<infer T>
                  ~~~~~~~~~~~~~~~~~~~~~~~~

  node_modules/@types/react/index.d.ts:2744:14
    2744         type LibraryManagedAttributes<C, P> = C extends React.MemoExoticComponent<infer T> | React.LazyExoticComponent<infer T>
                      ~~~~~~~~~~~~~~~~~~~~~~~~
    'LibraryManagedAttributes' was also declared here.

node_modules/@types/react/index.d.ts:2744:14 - error TS2300: Duplicate identifier 'LibraryManagedAttributes'.

2744         type LibraryManagedAttributes<C, P> = C extends React.MemoExoticComponent<infer T> | React.LazyExoticComponent<infer T>
                  ~~~~~~~~~~~~~~~~~~~~~~~~

  node_modules/@types/react-transition-group/node_modules/@types/react/index.d.ts:2746:14
    2746         type LibraryManagedAttributes<C, P> = C extends React.MemoExoticComponent<infer T> | React.LazyExoticComponent<infer T>
                      ~~~~~~~~~~~~~~~~~~~~~~~~
    'LibraryManagedAttributes' was also declared here.


Found 2 errors.

[trusktr]

My problem seems to be similar to #14179 (comment)

❯ npm ls @types/react                                                                                                                      ✹
mapper-saffron@2.0.37 /Users/joepea/src/Signafy+mapper-saffron
├─┬ @material-ui/core@3.9.2
│ └─┬ @types/react-transition-group@2.0.15
│   └── @types/react@16.8.2
├── @types/react@16.8.1
├─┬ @types/react-dom@16.8.0
│ └── @types/react@16.8.1  deduped
└─┬ @types/react-router-redux@5.0.17
  ├── @types/react@16.8.1  deduped
  └─┬ @types/react-router@4.4.3
    └── @types/react@16.8.1  deduped

So I unpinned the @types/react version.

[oliviertassinari]

@trusktr I think that your case is based on some strong foundation:

• No type packages in the dependencies of antd while it's written with TypeScript: https://unpkg.com/antd@3.13.2/package.json.
• Same with formik: https://unpkg.com/formik@1.5.0/package.json.

[eps1lon]

This isn't a bug or feature request, but I noticed that there are @types/ packages in the dependencies section of @material-ui/core. Shouldn't they be devDependencies instead? Or is there a reason for them to be dependencies?

If they were devDependencies then the wouldn't be installed by default. @types/* packages work the same way.

Basically:

• Do you use the types in your released declarations? -> dependency
• Otherwise -> devDependency

Issues with conflicting types/* packages is very frequent which is why libraries always use any version.

[oliviertassinari]

@eps1lon How do you explain the Antd and Formik tradeoff?

[eps1lon]

They're doing it wrong.

[trusktr]

@eps1lon Interesting.

Based on this question on Stack Overflow, it should be in dependencies if we are re-exporting a type for the end user to use, and otherwise it can stay in devDependencies.

I think this makes sense, because: if material-ui isn't re-exporting react-transition-group interfaces, then I won't interact with those interfaces, therefore I don't need the types, and I'll only care if I'm using the material-ui interfaces correctly.

If material-ui isn't exposing those interfaces to the end user, then only material-ui devs will care about those types during dev mode.

Quick question: is material-ui re-exporting react-transition-group to end users of material-ui?

[trusktr]

Maybe "re-exporting" isn't the right word. Are perhaps the react-transition-group types exposed the the users, for example as prop types to the material-ui components?

[trusktr]

Ah, I see the react-transition-group types are exposed here:

https://github.com/mui-org/material-ui/blob/674c523dffd0997f08154bc3c513e200823ee228/packages/material-ui/src/transitions/transition.d.ts#L23-L27

Alrighty, looks like they are required in dependencies then! 👍

[eps1lon]

We're extending a type. If we wouldn't list it as a dependency then users would have to manually add it or trigger errors when compiling. Essentially defeating the purpose of a package.json.

With react it's slightly different since you almost always have those types in your package anyway. A peerDependency would be the perfect candidate here but this will trigger warnings for non-ts users.

There's no silver bullet here at the moment. But I rather stick with the approach that the defacto standard types package uses.

[eps1lon]

They're doing it wrong.

Just to be clear I don't know if they have any actual dependency on types. I suspect they do not. They're following the same approach concerning peer type dependency as we do.