react-packager: Add ES6 import statement support to DependencyGraph.

[pilwon]

This PR teaches packager's DependencyGraph how to extract dependencies written with ES6 import statements.

It fixes the issue where you are not able to write your app with ES6 import statements when your custom transformer (replacing the default JSTransform, for example, babel) already supports the ES6 import syntax.

It will also be useful for JSTransform later on once it implements import feature too.

[jgable]

Does this just work for import blah from 'blah';? Would it work for all the proper import syntaxes?

[pilwon]

@jgable Yes, it supports all valid ES6 import syntaxes documented in the ES6 Language Specification.

You can see the result from a test ran against a comprehensive list of valid syntaxes in this gist.

[amasad]

We also need to make the change here https://github.com/pilwon/react-native/blob/packager-es6-import-patch/packager/react-packager/src/DependencyResolver/haste/index.js#L28
It'd be great if we can consolidate them.

[pilwon]

@amasad Sure I can add that to PR. I have a question:

Why does DependencyResolver use /require\(['"]([\.\/0-9A-Z_$\-]*)['"]\)/gi while DependencyGraph uses /\brequire\s*\(\s*[\'"]([^"\']+)["\']\s*\)/g? (they look quite different)

• Isn't the case-insensitive flag (/i) incorrectly applied? For example, there could be a line that calls a custom function defined as function ReQuire(str) {...}. That regex will match ReQuire(...) and replace the string param that has nothing to do with the module name passed to require().
• Is it okay \b is not present there? Wouldn't it match any function with suffix require? (ex: myrequire(...))

[pilwon]

@amasad PR #368 addressed above questions. I merged the latest code into this PR branch. Fixes #368 (comment) & test passes.

[amasad]

Thanks, will take a look shortly.

[amasad]

can you add test where there is no space between the comma and the default?

[amasad]

and a test where there are no spaces between the named imports and the { }

[amasad]

Looks good, let's just add a couple more tests

[pilwon]

@amasad I updated test cases so most of them are in a more widely used spacing styles:

import Default, { Foo, Bar as Baz, Qux as Norf } from 'x';

I still kept some different spacing style cases such as import 'x' ;, import {} from 'x';, import {Foo as Bar} from 'x';, and import Default , { } from 'x';.

Also added an incorrect statement import'x'; that is expected to be ignored by the replace regex.

[amasad]

Great, thanks for being very response, @pilwon!