Support import expressions in `pkl-gen-go`

[rohan-datar]

I have a number of pkl modules that use import expressions in place of import clauses to facilitate mocking for tests (following the pattern mentioned here. However pkl-gen-go cannot generate bindings for properties defined using import expressions. It would be great if we could have a way to generate bindings for those types.

[HT154]

If I'm interpreting things correctly, you're seeing unhelpful codegen because you have a untyped property:

resources = import("resources.pkl")
// read as: resources: unknown = import("resources.pkl")

Which generates as something like this:

type MyModule struct {
  Resources any `pkl:"resources"`
}

In this situation would actually recommend doing this instead:

import "resources.pkl" as _resources

resources: _resources

This will ensure the resources property is properly typed (not unknown, therefore codegen'd with a real type instead of any) while still letting you override or amend the property.

[rohan-datar]

Okay, the issue I'm actually having is slightly different than I originally thought. The problem is not codegen for an import expression. The issue seems to be from a glob import expression. I have a property that's meant to be used like this:

configData = import*("data/*.pkl")

In the base module, I tried to set it's type like this:

configData: Mapping<String, Module>

Which is the type returned by a glob import as far as I can tell.

However trying to codegen this results in this error:

–– Pkl Error ––
Cannot generate type Module as Go.

88 | throw("Cannot generate type \(type.referent.name) as Go.")
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.typegen#generateDeclaredType.<function#3> (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/typegen.pkl#L88-L88)

72 | let (mapped = seenMappings.findOrNull((it) -> it.source == referent))
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.typegen#generateDeclaredType.<function#2> (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/typegen.pkl#L72-L88)

71 | let (reflectee = type.referent.reflectee)
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.typegen#generateDeclaredType.<function#1> (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/typegen.pkl#L71-L88)

70 | let (referent = type.referent)
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.typegen#generateDeclaredType (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/typegen.pkl#L70-L88)

39 | generateDeclaredType(type, enclosing, seenMappings)
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.typegen#generateType (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/typegen.pkl#L39-L39)

121 | generateType(typeArgValue, enclosing, seenMappings)
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.typegen#generateMapping.<function#2>.elem (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/typegen.pkl#L121-L121)

44 | imports = key.imports + elem.imports
                             ^^^^
at pkl.golang.internal.Type#Map.imports (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/Type.pkl#L44-L44)

99 | .flatMap((f) -> f.type.imports)
                     ^^^^^^^^^^^^^^
at pkl.golang.internal.ClassGen#imports.<function#2> (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/ClassGen.pkl#L99-L99)

98 | (if (isAbstract) fields.values.filter((f) -> !f.isInherited) else fields.values)
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.golang.internal.ClassGen#imports (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/ClassGen.pkl#L98-L99)

39 | when (!imports.isEmpty) {
            ^^^^^^^
at pkl.golang.internal.ClassGen#contents (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/ClassGen.pkl#L39-L39)

117 | text = gen.contents
             ^^^^^^^^^^^^
at pkl.golang.internal.Package#output.files[#1].text (https://github.com/apple/pkl-go/tree/v0.12.0/codegen/src/internal/Package.pkl#L117-L117)

1 | output.files?.toMap()?.mapValues((_, it) -> it.text) ?? Map()
                                                ^^^^^^^
at repl:text.<function#1> (repl:text)

1 | output.files?.toMap()?.mapValues((_, it) -> it.text) ?? Map()
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at  (repl:text)

Is there some solution to this?

[HT154]

Are you expecting the modules matched by the glob to amend a specific module?

If so, you want the more specific type in your annotation:

import "ConfigData.pkl"

configData: Mapping<String, ConfigData> = import*("data/*.pkl")
// where every matched module extends ConfigData.pkl

If this is not the case, can you say more about what your desired code generation output would be?