is operator does not take current scope into account #213

New Issue

adam · 2025-12-30T01:22:17+01:00

adam commented

2025-12-30 01:22:17 +01:00

Originally created by @sin-ack on GitHub (Oct 8, 2024).

Reproducer:

class Foo {}
local classes = new Listing {
    Foo
}.toList()

function check(a: Any) = classes.any((cls) -> a is cls)
local foo = new Foo {}

result = check(foo)

Error message:

$ jpkl eval test.pkl
–– Pkl Error ––
Cannot find type `cls`.

6 | function check(a: Any) = classes.any((cls) -> a is cls)
                                                       ^^^
at test#check.<function#1> (file:///home/agni/test.pkl, line 6)

Searched in the following places:
* Module `test` and any supermodules
* Module `pkl#base`

6 | function check(a: Any) = classes.any((cls) -> a is cls)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at test#check (file:///home/agni/test.pkl, line 6)

9 | result = check(foo)
             ^^^^^^^^^^
at test#result (file:///home/agni/test.pkl, line 9)

106 | text = renderer.renderDocument(value)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
at pkl.base#Module.output.text (https://github.com/apple/pkl/blob/47f2143/stdlib/base.pkl#L106)

This is contradictory with List.filterIsInstance which can take an arbitrary class at evaluation time (from what I can understand).

Originally created by @sin-ack on GitHub (Oct 8, 2024). Reproducer: ```pkl class Foo {} local classes = new Listing { Foo }.toList() function check(a: Any) = classes.any((cls) -> a is cls) local foo = new Foo {} result = check(foo) ``` Error message: ``` $ jpkl eval test.pkl –– Pkl Error –– Cannot find type `cls`. 6 | function check(a: Any) = classes.any((cls) -> a is cls) ^^^ at test#check.<function#1> (file:///home/agni/test.pkl, line 6) Searched in the following places: * Module `test` and any supermodules * Module `pkl#base` 6 | function check(a: Any) = classes.any((cls) -> a is cls) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ at test#check (file:///home/agni/test.pkl, line 6) 9 | result = check(foo) ^^^^^^^^^^ at test#result (file:///home/agni/test.pkl, line 9) 106 | text = renderer.renderDocument(value) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ at pkl.base#Module.output.text (https://github.com/apple/pkl/blob/47f2143/stdlib/base.pkl#L106) ``` This is contradictory with `List.filterIsInstance` which _can_ take an arbitrary class at evaluation time (from what I can understand).

adam closed this issue

2025-12-30 01:22:17 +01:00

adam commented

2025-12-30 01:22:17 +01:00

@bioball commented on GitHub (Oct 8, 2024):

is accepts a type, rather than an expression, and types and values exist in different namespaces.

This is intentional, and changing this would be a breaking change for how is works. It's akin to is in Kotlin, Swift, etc.

@bioball commented on GitHub (Oct 8, 2024): `is` accepts a type, rather than an expression, and types and values exist in different namespaces. This is intentional, and changing this would be a breaking change for how `is` works. It's akin to `is` in Kotlin, Swift, etc.

adam commented

2025-12-30 01:22:18 +01:00

@sin-ack commented on GitHub (Oct 11, 2024):

Sorry for not getting back on this. I disagree with the decision but respect it. Is there a way to achieve what I want to do in Pkl, then, without resorting to tons of separate foo is Class checks?

@sin-ack commented on GitHub (Oct 11, 2024): Sorry for not getting back on this. I disagree with the decision but respect it. Is there a way to achieve what I want to do in Pkl, then, without resorting to tons of separate `foo is Class` checks?

adam commented

2025-12-30 01:22:18 +01:00

@bioball commented on GitHub (Oct 11, 2024):

You can compare the class values directly, e.g.

import "pkl:reflect"

class Foo {}
local classes = new Listing {
    Foo
}.toList()

function isClassOrSubclass(value: Any, clazz: Class?) =
  if (clazz == null) false
  else if (value.getClass() == clazz) true
  else
    isClassOrSubclass(value, reflect.Class(value).superclass?.reflectee)

function check(a: Any) = classes.any((it) -> isClassOrSubclass(a, it))

@bioball commented on GitHub (Oct 11, 2024): You can compare the class values directly, e.g. ```pkl import "pkl:reflect" class Foo {} local classes = new Listing { Foo }.toList() function isClassOrSubclass(value: Any, clazz: Class?) = if (clazz == null) false else if (value.getClass() == clazz) true else isClassOrSubclass(value, reflect.Class(value).superclass?.reflectee) function check(a: Any) = classes.any((it) -> isClassOrSubclass(a, it)) ```

adam commented

2025-12-30 01:22:18 +01:00

@sin-ack commented on GitHub (Oct 11, 2024):

That works, thanks for the solution.

@sin-ack commented on GitHub (Oct 11, 2024): That works, thanks for the solution.

adam commented

2025-12-30 01:22:19 +01:00

@odenix commented on GitHub (Oct 13, 2024):

@bioball How about adding method Class.isInstance(value) to base.Class?

@odenix commented on GitHub (Oct 13, 2024): @bioball How about adding method `Class.isInstance(value)` to `base.Class`?

adam commented

2025-12-30 01:22:19 +01:00