Better handling of untyped node module imports

[bterlson]

Consider importing an untyped module, eg. exceljs:

import exceljs = require('exceljs');

This results in an error that the module exceljs is not found. There is at least two ways to fix this:

1. Setting allowJs: true and maxNodeModulesJsDepth: 1
2. Declare an ambient module in a separate file

I think it would be better if instead we update module resolution semantics such that when we find an appropriate package.json without a typings entry, we store it away. Then if module resolution fails (ie. we also can't find an @types/exceljs), we go back and import the untyped package.json as a JS import. Thoughts?

You might argue that this should only be allowed with --allowJs, but it might also make sense to just always use this behavior when using node resolution rules as you may still not want to allow JS in your own project while still allowing your dependencies to be authored in JS without typings.

[aluanhaddad]

Is there anyway we can solve this in a non npm specific manner? I like the concept but tying it to node_modules/import_name and node_modules/@types/import_name is not something I would like to see.

[dmitriid]

Also, please, please, please improve documentation on "ambient modules". I've read the section seven times now, I still have no idea what the ambient modules are, how to define them and where to put the specs so that they are picked up by TS. Espec

It would be awesome, if there was a small section "you want to import module X. you create a file X.d.ts here. Then you do this and that and this"

[reverie]

I followed a chain of four closed tickets to get here. Glad to see the issue was addressed. Could someone please point to docs for this feature? How do I use it? For my sake, and for everyone else who may end up here. :)

[mhegazy]

This is part of typescript@2.1.3 release, so for now you will need npm install typescript@next.

Now having an import like import foo from "Foo" the compiler will check if there is a package Foo, e.g. node_modules\Foo\index.js if one is available, even if it does not have a .d.ts file along with it, no error will be reported. the type of the imports will be any.

if you use --noImplicitAny, you would get these import flagged as implicit anys.

hope that helps.