Discuss Apple's new schema driven Pkl config format

[kevinschaper]

Apple has a new config format that looks to be schema driven (defined as classes), with generators for json, yaml and code generators for Java, Kotlin and GO. Let's discuss the impact this might have on LinkML.

Should we make a gen-pkl?

The Java and Kotlin generators don't use templates, but instead use javapoet and kotlinpoet code generation libraries. Does anything like this exist for other languages we're supporting or in the python ecosystem?

[sneakers-the-rat]

sort of like an imperative wrapper to ast?

javapoet example:

MethodSpec main = MethodSpec.methodBuilder("main")
    .addModifiers(Modifier.PUBLIC, Modifier.STATIC)
    .returns(void.class)
    .addParameter(String[].class, "args")
    .addStatement("$T.out.println($S)", System.class, "Hello, JavaPoet!")
    .build();

TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld")
    .addModifiers(Modifier.PUBLIC, Modifier.FINAL)
    .addMethod(main)
    .build();

JavaFile javaFile = JavaFile.builder("com.example.helloworld", helloWorld)
    .build();

javaFile.writeTo(System.out);

declarative ast:

from ast import FunctionDef, Expr, Call, Name, Constant, ClassDef, Module

main = FunctionDef(
    name="main",
    body=[
        Expr(
            value=Call(
                func=Name(id="print"),
                args=[Constant(value="Hello, world!")],
            )
        )
    ],
    decorator_list=[Name(id="staticmethod")],
)

myclass = ClassDef(
    name="helloWorld",
    body=[main],
)

mymodule = Module(body=[myclass], type_ignores=[])

so then something like

class Builder():

    def __init__(self, **kwargs):
        self.fields = {}
        self.fields.update(kwargs)


    def __class_getitem__(cls, name: str):
        subcls = type(name, (cls,), {"type": getattr(ast, f"{name}Def")})
        return subcls

    def __getattr__(self, val:str):
        field = val.split('_')
        if field[0] == 'add':
            def adder(x):
                if field[1] not in self.fields:
                    self.fields[field[1]] = [x]
                else:
                    self.fields[field[1]].append(x)
                return self
            return adder
        else:
            raise ValueError(f'{val} {field} this is metaprogramming u expected it to make sense')

    def build(self):
        return self.type(**self.fields)

for

FunctionBuilder = Builder["Function"]
myfunc = FunctionBuilder(name="myfunction").add_body(ast.Pass())
myfunc.build()

or whatevs

[sneakers-the-rat]

It looks like javapoet is basically what we just added in the pydantic generator since it's not a full AST model but cheats in the bodies of methods by using strings. in general i'm not sure what 'builder' style classes add over normal classes where you could just do myclass.things.append(thing) instead of myclass.addthing(thing), but i mean if we want to do this then i am game

[cmungall]

I'm closing as we have a separate enhancement request for gen-pkl, but feel free to open a new discussion or reopen for discussion of more general leveraging of other libraries for codegen

#2169