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CoffeeScript now supports ES2015 modules #7818

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merged 5 commits into from
Sep 28, 2016
Merged

CoffeeScript now supports ES2015 modules #7818

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79ad443
Update CoffeeScript to 1.11.0, which supports modules; update check f…
GeoffreyBooth Sep 24, 2016
4c046fc
Add tests for imported modules using CoffeeScript’s new native import…
GeoffreyBooth Sep 24, 2016
e88abe6
Test that CoffeeScript native export statements work, by importing so…
GeoffreyBooth Sep 24, 2016
e1ac074
Improve regex
GeoffreyBooth Sep 26, 2016
3dbc956
Optimize regex
GeoffreyBooth Sep 26, 2016
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4 changes: 2 additions & 2 deletions packages/coffeescript/plugin/compile-coffeescript.js
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Expand Up @@ -83,8 +83,8 @@ export class CoffeeCompiler extends CachingCompiler {

let sourceMap = JSON.parse(output.v3SourceMap);

if (source.match(/(`|import|export|function\*)/)) {
// If source contains backticks or ES2015+ features,
if (source.match(/`|\bimport\b|\bexport\b|\byield\b/)) {
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The following should have a noticeable performance increase over this, especially on larger files:

source.match(/`|\b(?:import|export|yield)\b/)

And if attempting to eliminate some false-positives, perhaps:

source.match(/`|(?:;|^)\h*\b(?:import|export|yield)\b/)

Though I'd venture to say that it might be possible to break this logic – haven't given it a lot of thought. My assumption here is that import/export/yield are either at the beginning of a line or after a semi-colon, proceeded by optional whitespace.

Again, any benchmarks you could run here might be nice to see. Setting the env. variable METEOR_PROFILE=50 might be your friend in seeing the differences in compilation time.

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import or export by definition need to be at the beginning of a line, which in CoffeeScript means they follow a newline (no semicolons). yield would usually begin a line after some whitespace; I’m not sure if it could ever not start a line, but it might.

I can’t imagine it that takes more time to run this match than it does to recompile with Babel. Assuming most projects don’t use features that generate ES2015 code, which I think is a pretty safe assumption, this regex should be saving us time. And most projects that do generate ES2015 probably are doing so because of modules, which means this regex finds a match almost immediately, from the top of the file, so the match should be a very minor performance hit.

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import or export by definition need to be at the beginning of a line, which in CoffeeScript means they follow a newline (no semicolons)

Not common, but CoffeeScript actually can have semi-colons. But based on your description, my second regex above should work but would need the /m modifier. Again though, this only eliminates some potential false positives.

I can’t imagine it that takes more time to run this match than it does to recompile with Babel. Assuming most projects don’t use features that generate ES2015 code, which I think is a pretty safe assumption, this regex should be saving us time. And most projects that do generate ES2015 probably are doing so because of modules, which means this regex finds a match almost immediately, from the top of the file, so the match should be a very minor performance hit.

Agree, with the same assumptions. Though I'd still recommend the first regex change regardless.

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So which regex would you recommend? /|\b(?:import|export|yield)\b/`?

FWIW I think import is the most likely substring that a file would contain, and most likely to be first. Backticks are probably last.

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My vote would still be that, just for readability. The back-tick at the end is harder to see and the difference is extremely negligible that that point. 😄

// If source contains backticks or features that output as ES2015+,
// pass the coffee output through babel-compiler
const doubleRoastedCoffee =
this.babelCompiler.processOneFileForTarget(inputFile, output.js);
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