starlark-go VS starlark

The python-esque sandboxed language is Starlark: https://github.com/google/starlark-go#documentation

Clace is built in go as a reverse proxy. Clace uses https://github.com/google/starlark-go as its configuration language. This allows full Hypermedia driven apps to be built in Clace, running within the main Clace process. For example:

  clace app create --approve github.com/claceio/apps/system/disk_usage /disk_usage

Starlark in go https://github.com/google/starlark-go is a great way to combine the best of both, the ease of use of Python and the simplicity of go.

I have been building a platform for deploying internal web applications using this approach https://github.com/claceio/clace. Use Starlark to configure the application, the platform itself is built in go.

The big unknown is your task definition: what does user-defined logic look like? If you're expecting go code, that's gonna need some cleverness because of the compiled nature of it. There's a node runtime implemented in go if you want to provide sandboxed javascript (check the source of k6.io, it's the main one I know that uses it). If you want to provide building blocks and let them compose them, starlark might be a good choice.

Another one of those (with broader language support) is the Starlark language, which has a Go implementation: https://github.com/google/starlark-go

Every config format gets as complex to be touring complete in the end. We had similar problems and eventually got rid of that complexity and switched to starlark (the bazel config language), was a huge benefit for the tools. https://github.com/google/starlark-go "Starlark is a dialect of Python intended for use as a configuration language. Like Python, it is an untyped dynamic language with high-level data types, first-class functions with lexical scope, and garbage collection."

Direct link to the Go implementation of Starlark: https://github.com/google/starlark-go

For a Python-like syntax, https://github.com/google/starlark-go is the language used in Babel. It's very mature, but since it is used in a massive mature project with a specific purpose, it doesn't move fast or drift from the spec of its Java-based sibling. It doesn't have exception try except blocks or some other features you might expect, but for short extension logic, it might be exactly what you want with the stability you can depend upon.

I actually like Deno's take on things, the ability to "drop privs" (or "allow-list") is super powerful.

Starlark is supposedly a limited version of python (https://github.com/bazelbuild/starlark), but what if you could say in python itself:

    def foo():

— a in b not in c

WalterBright mentioned that D will give you an error. When designing Starlark (a derivative of Python), I also decided to give an error for this, by making the comparison operators non associative.

https://github.com/bazelbuild/starlark/blob/master/design.md...

I agree this Python feature can look cute, but I've found it's rarely useful and can easily be avoided.

Having done some nontrivial Bazel/Starlark hacking, I completely agree that lightweight static types would be a good usability improvement. But I want to point out that Starlark is actually not Turing complete, which is imo one of the more interesting characteristics it has. Recursion is forbidden (https://github.com/bazelbuild/starlark/blob/master/spec.md#f...) and loops must be structural; there is no while loop or other unbounded iteration construct. Starlark is one of the more capable and mainstream non-Turing-complete languages out there, and doesn't resemble the other common ones which mostly show up in theorem provers. On the one hand I think the logic in a build system that needs to reason about incremental builds absolutely should be guaranteed to terminate, but in some particularly painful situations I've had to resort to iteration over smart-contract-style "gas" parameters.

The implementations and users page mentioned above:

https://github.com/bazelbuild/starlark/blob/master/users.md

Starlark: Starlark is a language for describing build transformations, inspired by Python, but with features that make it suitable for embedding in software like Bazel. It can be used for configuration generation due to its capability for deterministic evaluation and expressing complex build transformations.

In the design of Starlark (https://github.com/bazelbuild/starlark), I often had to push back against new feature requests to keep the language simple. I explicitly listed simplicity as a design goal.i

Of course, the scope of the language is not the same as general purpose languages, but there's always pressure from the users to add more things. I also think many people underestimate the cost of adding new features: it's not just about adding the code in every compiler/interpreter, specifying every edge-case in a spec, updating all the tooling for the language and writing tutorials; it's also a cost on everyone who will have to read any of the code.