Comment by indygreg2 | Hacker News Reader

Comment by indygreg2 | Hacker News Reader

I converted PyOxidizer's configuration files from TOML to Starlark because I found it effectively impossible to express complex primitives in a static configuration file and the static nature was constraining end-user utility.

A common solution to this problem is to invent some kind of templating or pre-evaluation of your static config file. But I find these solutions quickly externalize a lot of complexity and are frustrating because it is often difficult to debug their evaluation.

At the point you want to do programming-like things in a config file, you might as well use a "real" programming language. Yes, it is complex in its own way. But if your target audience is programmers, I think it is an easy decision to justify.

I'm extremely happy with Starlark and PyOxidizer's configuration files are vastly more powerful than the TOML ones were.

https://pyoxidizer.readthedocs.io/en/stable/config.html

> I found it effectively impossible to express complex primitives in a static configuration file

I don't quite understand this part. Any examples?

Compare https://pyoxidizer.readthedocs.io/en/v0.4.0/config.html#file... to https://pyoxidizer.readthedocs.io/en/stable/config.html#file....

In PyOxidizer's case, I wanted to create virtual pipelines of actions to perform. In TOML, we could create sections to express each stage in a logical pipeline. But if you wanted to share stages between pipelines, you were out of luck. With Starlark, you can define a stage as a function and have multiple functions reference it because is "just" calling a function.

I suppose I could have defined names for stages and made this work in TOML. So let's use a slightly more complicated example.

PyOxidizer config files need to allow filtering of resources. Essentially, call fn(x) to determine whether something is relevant. In the TOML world, we had to define explicit stages that applied filtering semantics: there were config primitives dedicated to applying filtering logic. PyOxidizer's config files had to expose primitives that could perform filtering logic desired by end-users. By contrast, Starlark exposes an iterable of objects and config files can examine attributes of each object and deploy their own logic for determining whether said object is relevant. This is far more powerful, as config files can define their own filtering rules in a programming language without being constrained by what the TOML-based config syntax supports.

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