Scripty：轻量级嵌入式脚本语言

Scripty is an extremely simple (and deliberately limited) scripting language meant to be embedded in strings or other similar constructs, usually in a host document format (but not only).It looks like this: $site.page('blog').subpages().first().title.However, whether your evaluation context is made up of ‘sites’, ‘pages’ and ‘titles’, rather than ‘tables’, ‘bank accounts’, ‘musical notes’, ‘apple pies’ or anything else, that’s entirely up to you.Scripty allows you to provide an evaluation context that defines primitive and aggregate types, and also which methods can be called on them.Lastly, Scripty has no for loops, if statements or variable assignment. A Scripty program is just a single expression, so one way of thinking about it is as a framework for building simple query languages.I’ve been using Scripty for a while now as part of Zine, my static site generator, but until now I never really spent effort trying to make it usable for other people.So recently I set out to provide an example implementation, and in the process I’ve implemented a few simplifications that I thought about in the past but that I never bothered actually implementing.Setting up a Scripty VM requires being familiar with Zig, but it’s otherwise pretty easy, see https://github.com/kristoff-it/scripty.VM implementationThe Scripty VM is a stack-based interpreter. A parser produces nodes that get analyzed and pushed onto the stack, and on function call application (when a ) token is seen), some values are popped off the stack, the function call is performed, and the resulting value is pushed back on the stack.I would describe this implementation as mostly naive, although I do get a bit clever with MultiArrayList (struct of arrays), but overall this is good enough for Zine as it’s still one of the fastest static site generators that I know of (this blog builds in less than 20ms on a Mac Mini M2 Pro and evaluation of Scripty expressions is a minuscule fraction of that time).I’ve also given this implementation a good amount of fuzzing with AFL, although this code is now gone, to be replaced by a native Zig fuzzer implementation.Future workI’m purposefully keeping Scripty very simple in order to support static analysis and compilation in the future.In Zine I already have a system to generate reference docs for SuperMD documents and SuperHTML templates (SuperMD, SuperHTML), but it’s a bespoke system that is not directly driven by the Scripty implementation (although it’s not too hard to make it yourself, it’s just a matter of adding extra definitions to your Scripty evaluation context definition and then using Zig comptime reflection to generate the docs).On the subject of static analysis it would also be nice to have a way for the SuperHTML language server to provide autocomplete suggestions for Scripty expressions, something that is currently not available.Lastly, being able to compile Scripty expressions to native code would be a stepping stone towards being able to compile SuperHTML templates (and of course any other host language that other people might end up using Scripty with). My plan in this regard is to use Zig as the target and then let the Zig compiler do all the heavy lifting.I plan to get to all of these things (roughly in this same order, so docs first, compiler last), in the not-too-far future, but I am currently putting more effort into another somewhat ambitious project so it might take a bit before I circle back to Scripty.Scripty flavorsOne reason why I believe that Scripty is of some value despite its extreme simplicity, is how you can still use it to produce very different user experiences.The example of Scripty expression that I showed at the beginning is inspired by SuperHTML, where Scripty expressions are placed in HTML attributes and used to generate HTML code accordingly.$site.homepage.subpages().first().link()

In this example we navigate from what is presumably a Site struct, into an instance of a page, and so on.In SuperMD Scripty is used in a completely different way. Without getting too deep into the weeds of how SuperMD works, take a look at this example usage:$video.asset('video.mp4').autoplay(true).muted(false)

In SuperMD Scripty is used as a “builder”/“fluent” interface in order to define embeds. In this example we are defining a video embed and then setting some of its properties. Every function call sets a property on the original embed definition and then returns the mutated value so that the subsequent function call can do the same, and so forth.In ConclusionWhen I originally set out to implement Scripty it was as part of my effort to create a new HTML templating language (which then became SuperHTML). I had reached a breaking point with Hugo’s templating language and decided to free myself from having to use curly-braced templating languages (which are essentially macros, and I hate macros).The realization I had in the process is that all these templating languages (and not only) have essentially two languages in them: one to build expressions, and one to interoperate with the outer document.So I decided to make them truly separate languages, and the result is a tiny language that can both be very easy to get used to (it’s essentially just field navigation and function calls, no monkey business), but that can also be tailored to each specific use case by designing the evaluation context accordingly.

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