Injecting data and objects

[obj-p]

Kudos on pkl. Really great tooling and etc.

I'm still getting my bearings on everything and was curious if it's possible to evaluate a configuration and then inject data or other instances to make for a more dynamic configuration.

For example, we are considering this to template out our screens as driven from the backend. Certain UI elements may depend on dynamic data like a list view. Some strings may depend on a localized translation instance.

We have been spiking this with Kotlin Script but I love that this configuration language is not a full runtime like a JVM and it supports other language stacks.

Cheers! I'll continue to explore the experimental packages and how to extend pkl at the evaluation level.

EDIT:

As an example, our Kotlin Script templating evaluates to a class definition that specifies a constructor. The constructor then can be read through Kotlin reflection and data may be injected accordingly...

[obj-p]

Actually thinking about it more.. I can probably just use a method on an outer type that acts like a constructor I had mentioned in my post.

[bioball]

There's kind of two approaches here that I can think of.

One is to use external properties to make values available to Pkl:

foo = read?("prop:foo") ?? 15

You can use a non-nullable read too if the prop is required:

foo = read("prop:foo")

Or if you want to get all properties, you can use a globbed read:

allProps = read*("prop:**")
foo = allProps["prop:foo"]

Another approach is, if you need to ad-hoc change a value that isn't defined in terms of read("prop:"), is to evaluate an expression that changes a value:

// someModule.pkl
foo = 15

pkl eval someModule.pkl -x "(module) { foo = 35 }"

There's the equivalent of pkl eval -x in the Java API, and also in the Gradle plugin.