Add compatibility support for a few more type overrides

README.md

@@ -65,7 +65,7 @@ Until then, minor and patch releases may contain breaking changes.
 ### Known Current Limitations
 
 - **Inlined imports**: Imported Pkl types are inlined into the output TypeScript file. For example, if `foo.pkl` has an import like `import "bar.pkl"`, and you run `pkl-gen-typescript foo.pkl`, the resulting `foo.pkl.ts` file will include all types defined in `foo.pkl` _as well as_ all types defined in `bar.pkl`. This means that the resulting TypeScript generated files (in a multi-file codegen) will match the set of input root files, not the file structure of the source Pkl files. This behaviour may create unintended name conflicts; these can be resolved using the `@typescript.Name { value = "..." }` annotation. It may also cause duplication (eg. if the same shared Pkl library file is imported in two schemas); TypeScript's structural typing (where equivalent type shapes can be used interchangeably) should mean that any duplicate types can be safely used as each other.
-- **Subclass type overrides**: Pkl class definitions are generated as TypeScript interfaces in code generation; Pkl supports completely changing the type of a property in a child class, but this is not allowed in TypeScript extending interfaces. When a TypeScript interface `extends` a parent interface, overrides of the type of a property must be "compatible" with the parent type (eg. overriding a `string` type with a string-literal type). In TypeScript codegen, overriding a parent string-type property with a string literal type is allowed, and other compatible types may be allowed in the future (if you have an example of where this would be useful, please file a GitHub Issue).
+- **Subclass type overrides**: Pkl class definitions are generated as TypeScript interfaces in code generation; Pkl supports completely changing the type of a property in a child class, but this is not allowed in TypeScript extending interfaces. When a TypeScript interface `extends` a parent interface, overrides of the type of a property must be "compatible" with the parent type (eg. overriding a `string` type with a string-literal type). TypeScript codegen currently has support for a few compatible types, and others may be allowed in the future (if you have an example of a compatible type that should work but fails in codegen, please file a GitHub Issue).
 - **Regex deserialisation**: Pkl's `Regex` type will be decoded as a `pklTypescript.Regex` object, which contains a `.pattern` property. Pkl uses Java's regular expression syntax, which may not always be perfectly compatible with JavaScript's regular expression syntax. If you want to use your Pkl `Regex` as a JavaScript `RegExp`, and you are confident that the expression will behave the same way in JavaScript as in Pkl, you can instantiate a new `RegExp` using the `pklTypescript.Regex.pattern` property, eg. `const myConfigRegexp = new RegExp(myConfig.someRegex.pattern)`.
 - **IntSeq deserialisation**: Pkl's `IntSeq` type is intended to be used internally within a Pkl program to create a range loop. It is unlikely to be useful as a property type in JavaScript, and is therefore decoded into a custom `pklTypescript.IntSeq` type with signature `{ start: number; end: number: step: number }` - it is _not_ decoded into an array containing the ranged values. If you have a use-case to use `IntSeq` as an array of ranged values in a TypeScript program, please file a GitHub Issue.
 - **Duration and DataSize APIs**: Pkl has a rich API for many of its custom types, but two of note (that are not common in standard libraries of other languages) are `Duration` and `DataSize`, which include convenience APIs for eg. converting between units or summing values. These types are decoded into `pklTypescript.DataSize`/`pklTypescript.Duration` types (each of which have a `value` and `unit` property), and do not yet have the convenience APIs from Pkl.

codegen/snippet-tests/input/04-withClass.pkl

@@ -8,9 +8,21 @@ value: MyCustomClass
 abstract class MyAbstractClass {
   someString: String
   overrideableStringType: String
+  overridableListing1: Listing<String | Int>
+  overridableListing2: Listing<String | Int>
+  overridableMap1: Map<String, String | Int>
+  overridableMap2: Map<String, String | Int>
+  overridableUnion1: Int|String|List<String>
+  overridableUnion2: Int|String
 }
 
 class MyConcreteClass extends MyAbstractClass {
   anotherString: String
   overrideableStringType: "string literal type"
+  overridableListing1: Listing<Int | String>
+  overridableListing2: Listing<String>
+  overridableMap1: Map<String, Int | String>
+  overridableMap2: Map<String, String>
+  overridableUnion1: String|Int
+  overridableUnion2: String
 }

codegen/snippet-tests/output/04_with_class.pkl.ts

@@ -21,13 +21,37 @@ export interface MyAbstractClass {
   someString: string
 
   overrideableStringType: string
+
+  overridableListing1: Array<string | number>
+
+  overridableListing2: Array<string | number>
+
+  overridableMap1: Map<string, string | number>
+
+  overridableMap2: Map<string, string | number>
+
+  overridableUnion1: number | string | Array<string>
+
+  overridableUnion2: number | string
 }
 
 // Ref: Pkl class `04-withClass.MyConcreteClass`.
 export interface MyConcreteClass extends MyAbstractClass {
   anotherString: string
 
   overrideableStringType: "string literal type"
+
+  overridableListing1: Array<number | string>
+
+  overridableListing2: Array<string>
+
+  overridableMap1: Map<string, number | string>
+
+  overridableMap2: Map<string, string>
+
+  overridableUnion1: string | number
+
+  overridableUnion2: string
 }
 
 // LoadFromPath loads the pkl module at the given path and evaluates it into a N04WithClass

codegen/src/internal/ClassGen.pkl

@@ -46,7 +46,11 @@ local function getAllProperties(clazz: reflect.Class?): List<reflect.Property> =
 
 local function isSameType(typeA: reflect.Type, typeB: reflect.Type) =
   if (typeA is reflect.DeclaredType && typeB is reflect.DeclaredType)
-    typeA.referent.reflectee == typeB.referent.reflectee
+    typeA.referent.reflectee == typeB.referent.reflectee &&
+    typeA.typeArguments.length == typeB.typeArguments.length &&
+    typeA.typeArguments
+      .zip(typeB.typeArguments)
+      .every((pair) -> isSameType(pair.first, pair.second))
   else if (typeA is reflect.NullableType && typeB is reflect.NullableType)
     isSameType(typeA.member, typeB.member)
   else if (typeA is reflect.NothingType && typeB is reflect.NothingType)
@@ -57,8 +61,8 @@ local function isSameType(typeA: reflect.Type, typeB: reflect.Type) =
     typeA.value == typeB.value
   else if (typeA is reflect.UnionType && typeB is reflect.UnionType)
     typeA.members.length == typeB.members.length &&
-    typeA.members
-      .zip(typeB.members)
+    typeA.members.sortBy((m) -> m.referent.reflectee.toString())
+      .zip(typeB.members.sortBy((m) -> m.referent.reflectee.toString()))
       .every((pair) -> isSameType(pair.first, pair.second))
   // remaining types: `FunctionType`, `TypeParameter`, `ModuleType`.
   // we can actually check if `ModuleType` refers to the same type by checking if the enclosing declaration is the same,
@@ -70,9 +74,42 @@ local function isSameType(typeA: reflect.Type, typeB: reflect.Type) =
 // the only current supported way below, is when the parent type is String-type, and the child type is a string-literal type.
 // In the future we could add more detailed compatibility checks.
 local function isCompatibleType(parentType: reflect.Type, childType: reflect.Type) =
-  parentType is reflect.DeclaredType &&
-  parentType == reflect.stringType &&
-  childType is reflect.StringLiteralType
+  (
+    parentType is reflect.DeclaredType &&
+    (
+      (
+        // String type can be overridden by string literal type
+        parentType == reflect.stringType &&
+        childType is reflect.StringLiteralType
+      ) ||
+      (
+        // Same type, different but compatible type arguments
+        childType is reflect.DeclaredType &&
+        parentType.referent.reflectee == childType.referent.reflectee &&
+        (
+          parentType.typeArguments
+            .zip(childType.typeArguments)
+            .every((pair) ->
+              isSameType(pair.first, pair.second) ||
+              isCompatibleType(pair.first, pair.second)
+            )
+        )
+      )
+    )
+  )
+  ||
+  (
+    parentType is reflect.UnionType &&
+    (
+      (
+        // Child union can be a subset of the parent union's members
+        childType is reflect.UnionType &&
+        childType.members.every((m) -> parentType.members.contains(m))
+      )
+      // Or child type can be one of the types from the parent union
+      || parentType.members.contains(childType)
+    )
+  )
 
 // visible for testing
 function getFields(