A Grammar for HTML Twirl Templates with Play Framework on Scala

This repository attempts to apply a grammar that will tokenise basic components of Twirl templates, for use with Scala and the Play Framework.

At the moment, the root of this repository functions as a vscode extension and as such, has been tested on the VSC editor. There are, however, some limitations to the grammar. There is unfortunately only so much I can do with regexes and TextMate's begin/end/match.

You may apply this vscode extension by cloning this repository, opening it in VSCode, and then navigating to Run > Start Debugging. A pop-up "Extension Host" window will appear. Open a Play project in this extension host window, and navigate to a Twirl HTML file. If everything works as expected, then you should hopefully see some helpful syntax highlighting for your Twirl template.

I have tried my best to make something that is decent-enough to use and that works to the best of my ability. I have little experience with TextMate and the Oniguruma regex engine it uses.

Known Limitations

Wherever embedded Scala is detected, the source.scala grammar is used. This is to reduce the complexity of this grammar and keep it aligned with the goal of trying to bring some form of tokenisation support for Twirl template files. This is still considerably better than... well, nothing. This has some downsides though - it seems that the source.scala scope that I am using for embedded Scala is, in fact, not designed for embedded Scala and therefore can be a bit aggressive with its matches. There are potentially similar issues with other embedded languages that also have a grammar written for them.

So far, only Twirl HTML is supported. As it stands, it is not likely that there will be additions of Twirl JS and Twirl XML as these aren't really popular enough. There is a chance that this may be done at some point in the future, but this is not something that will be supported as the v1 draft.

• any inline @... Scala code will be missed inside HTML tags. The alternative here was to effectively re-implement the HTML grammar to also match the patterns introduced in this grammar. Eg <div class="g" @t>, @t will instead be coloured and parsed as an HTML tag. This can then lead to further pains as if there is a method call that contains a parameter list which is a string, then this will cause an invalid illegal token to be reported by the HTML grammar and will result in a rather scary-looking red marker. This can be quite jarring for a relatively commonly used Play pattnern. See #5 for more info (child of parent issue #4). Any help here would be appreciated.

The general way of going around this may be to trust your eyes and intuition as opposed to relying solely on the grammar or assuming that it is 100% correct, 100% of the time.

Maintained by: Asad Humayun