Suggestion: string interpolation

[RyanCavanaugh]

Support ES6-style template strings

http://tc39wiki.calculist.org/es6/template-strings/

To be determined: Can we generate code for pre-ES6 targets? What does that look like?

[duncanmak]

I'm interested in working on this. I had a local fork for the 0.9 compiler that included parser changes to allow foo strings, and was preparing to start working on emitting code.

With the new compiler work underway, what's the best way for an external contributor to help out here?

[mhegazy]

Thanks @duncanmak, a PR would be a good way to share your proposal with us. Since this is a bigger change than normal bug fixes, I would suggest sharing your changes early so that you can get feedback as you go.

Feel free to tag me, or email me directly if you have any questions.

Please follow the guidelines in CONTRIBUTING.md and submit a Contributor License Agreement (CLA) before submitting the pull request.

[basarat]

:+1:

Codeplex issue : https://typescript.codeplex.com/workitem/19

[styfle]

This would be great to have in TypeScript :+1:

[BurtHarris]

+1: A highly desirable enhancement.

[ryanbnl]

Unless I'm missing something, codegen for < ES6 should be just a case of removing the line-end character(s) and correctly escaping single and double-quote.

[ryanbnl]

It would be especially nice if this were to support type annotations which could be determined in the lexer. So you could annotate a string as containing HTML which editors could use to provide highlighting, autocomplete etc.

Or better yet, something similar to Nemerle's macros (see: http://nemerle.org/About).

[DanielRosenwasser]

As a heads up, I'm currently taking this on.

[DanielRosenwasser]

Implemented in #960 and #1072.

There are still some details being ironed out, but we support tagged templates on ES6 emit and untagged templates on all emit targets.

Type-checking occurs in substitution expressions, however, in an untagged template expression, there is no constraint on the type of the substitution expressions.

In a tagged template, overload resolution may occur, yielding an appropriate signature. Substitution expressions are constrained by the signature's parameters' types. A synthesized value of the new TemplateStringsArray type corresponds to the first argument. Substitution expressions at position n correspond to an argument at position n+1. Contextual typing rules work as appropriate.

Language service support for signature help on tagged templates is in the works on #1204.

[hdachev]

Hey Daniel, This feature is a massive win, thanks for implementing. Any chance on tagged templates getting es5 support? Is it not a more or less straightforward transformation - perhaps a __template(tag, strings, values) function emitted to package the string arrays and invoke the tag? Thanks again!

[DanielRosenwasser]

Hey @hdachev,

Really glad that you've had a good experience with this feature. Downleveled ES3/ES5 tagged templates is actually on our agenda, and @ivogabe has put out PR #1589 to implement them. So far, things look good, and I think we'll be able to lock it in for 1.5.

[hdachev]

Thanks, great work guys!

On Wednesday, February 11, 2015, Daniel Rosenwasser < notifications@github.com> wrote:

Hey @hdachev https://github.com/hdachev,

Really glad that you've had a good experience from this feature. Downleveled ES3/ES5 tagged templates is actually on our agenda, and @ivogabe https://github.com/ivogabe has put out PR #1589 https://github.com/Microsoft/TypeScript/pull/1589 to implement them. So far, things look good, and I think we'll be able to lock it in for 1.5.

— Reply to this email directly or view it on GitHub https://github.com/Microsoft/TypeScript/issues/13#issuecomment-73843673.

[mindplay-dk]

So we have string interpolation, and support for tagged templates coming up in 1.5 - these are great features, but has anyone thought about adding support for an alternative file extension for template files?

Basically just Typescript, but with the contents of the file being emitted or returned somehow, and you have to use a tag to escape from output - I guess basically EJS for Typescript.

There are lots of fine template engines for JS, but what I'm after is something that will receive the same excellent IDE support Typescript gets - I haven't found anything like that for JS. (we're a rather large team considering a transition from PHP towards Typescript+Node, and a key missing feature right now is views/templates with proper IDE support, e.g. auto-complete for a view-model and view helper-functions.)

[basarat]

@mindplay-dk I suspect this might just happen with angular support followed by angular support for server side next year.