Add typings

[ChristianMurphy]

typings are based off types available in definitely typed,
and have been updated to add type predicate support,
meaning when unist-util-is is used as an if conditional, everything
inside the conditional scope can use the narrowed type.

[ChristianMurphy]

/cc @Rokt33r

[ChristianMurphy]

📓 NOTE: this is a breaking change, type predicates require TypeScript version 3 or higher.
Previously typings were designed for TypeScript 2.

[ChristianMurphy]

The difference in use

// before
if (is('heading', node)) {
  const typedNode = node as Heading
  // do something
}

// after
if (is<Heading>('heading', node)) {
  // node is automatically type Heading within this scope
  // do something
}

[Rokt33r]

LGTM! 😍 😍 😍

[wooorm]

One Q: is convert.d.ts correctly picked up, when published and installed? I believe types/tsconfig.json defines paths, but it isn’t published, and package.json defines the main definitions only?

[Rokt33r]

@wooorm I think I should try it. I'll let you know if it is good or not.

[Rokt33r]

@ChristianMurphy
It seems those type testings don't work well with typescript@next(3.6.0-dev.20190724) now.

Error: /Users/junyoung/Code/unist-util-is/unist-util-is-test.ts:98:1
ERROR: 98:1   expect  TypeScript@next: Expected an error on this line, but found none.
ERROR: 109:1  expect  TypeScript@next: Expected an error on this line, but found none.
ERROR: 190:1  expect  TypeScript@next: Expected an error on this line, but found none.

I guess it should be better to do the test with the current local typescript installation. IMO, testing with unstable build feels a bit ridiculous.

If we want to do so, we need to provide --localTs option like the below.

    "test-types": "dtslint . --localTs node_modules/typescript/lib",

[ChristianMurphy]

Thanks @Rokt33r!
Flattened types in this PR

[ChristianMurphy]

@Rokt33r I tested with typescript@3.6.0-beta I am not seeing the issue.

➜  npm i -D typescript@beta
npm WARN tslint@5.14.0 requires a peer of typescript@>=2.1.0 || >=2.1.0-dev || >=2.2.0-dev || >=2.3.0-dev || >=2.4.0-dev || >=2.5.0-dev || >=2.6.0-dev || >=2.7.0-dev || >=2.8.0-dev || >=2.9.0-dev || >=3.0.0-dev || >= 3.1.0-dev || >= 3.2.0-dev but none is installed. You must install peer dependencies yourself.
npm WARN tsutils@2.29.0 requires a peer of typescript@>=2.1.0 || >=2.1.0-dev || >=2.2.0-dev || >=2.3.0-dev || >=2.4.0-dev || >=2.5.0-dev || >=2.6.0-dev || >=2.7.0-dev || >=2.8.0-dev || >=2.9.0-dev || >= 3.0.0-dev || >= 3.1.0-dev but none is installed. You must install peer dependencies yourself.
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.9 (node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.9: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})

+ typescript@3.6.0-beta
updated 1 package and audited 6893 packages in 19.956s
➜ npm run test-types 

> unist-util-is@3.0.0 test-types ~/unist-util-is
> dtslint . --localTs node_modules/typescript/lib

[ChristianMurphy]

Oddly enough, I'm also not able to reproduce the issue on the next version. 🤔

$ npx envinfo --npmPackages                 
npx: installed 1 in 1.214s

  npmPackages:
    browserify: ^16.0.0 => 16.3.0 
    dtslint: ^0.9.0 => 0.9.0 
    nyc: ^14.0.0 => 14.1.1 
    prettier: ^1.0.0 => 1.18.2 
    remark-cli: ^6.0.0 => 6.0.1 
    remark-preset-wooorm: ^5.0.0 => 5.0.0 
    tape: ^4.0.0 => 4.11.0 
    tinyify: ^2.0.0 => 2.5.1 
    typescript: ^3.6.0-dev.20190724 => 3.6.0-dev.20190724 
    unified: ^8.3.2 => 8.3.2 
    xo: ^0.24.0 => 0.24.0 


$ node --version
v12.6.0

$ npm --version
6.9.0

$ npx dtslint . --localTs node_modules/typescript/lib

[Rokt33r]

@ChristianMurphy It works again after I flushed ~/.dts. Maybe the build in my mac was wrong.

It looks good to be merged now. 😄

[ChristianMurphy]

Thanks for double checking @Rokt33r 🙇‍♂️

---

@wooorm merging this in now, the changes to rely on TypeScript 3 will make this a SemVer major update.