Mention type unsoundness of serializer() in the documentation
#2998
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Pull Request Overview
This PR updates the documentation for various serializer() overloads to mention that type unsoundness may result in incorrect results or [ClassCastException] if improperly used.
- Added a clear Pitfall section warning against potential type mismatches.
- Revised examples and wording in multiple serializer() overloads to improve clarity.
dkhalanskyjb
commented
Apr 28, 2025
| @@ -58,14 +58,14 @@ public inline fun <reified T> SerializersModule.serializer(): KSerializer<T> { | |||
| * Creates a serializer for the given [type]. | |||
| * [type] argument is usually obtained with [typeOf] method. | |||
| * | |||
| * This overload works with full type information, including type arguments and nullability, | |||
| * and is a recommended way to retrieve a serializer. | |||
| * For example, `serializer<typeOf<List<String?>>>()` returns [KSerializer] that is able | |||
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I don't know what this dependent-type-style syntax means and was assuming that this was a copy-paste artifact of some sort.
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I think I mistyped the function call: it should be serializer(typeOf<List<String?>>()). Can you please bring this paragraph back in the correct form?
sandwwraith
requested changes
Jun 25, 2025
| @@ -60,12 +60,17 @@ public inline fun <reified T> SerializersModule.serializer(): KSerializer<T> { | |||
| * | |||
| * This overload works with full type information, including type arguments and nullability, | |||
| * and is a recommended way to retrieve a serializer. | |||
| * For example, `serializer<typeOf<List<String?>>>()` returns [KSerializer] that is able | |||
| * to serialize and deserialize list of nullable strings — i.e. `ListSerializer(String.serializer().nullable)`. | |||
| * For example, `serializerOrNull(typeOf<List<String?>>)` returns [KSerializer] that is able | |||
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Suggested change
| * For example, `serializerOrNull(typeOf<List<String?>>)` returns [KSerializer] that is able | |
| * For example, `serializer(typeOf<List<String?>>())` returns [KSerializer] that is able |
This is documentation for regular serializer() function, and typeOf needs invocation
| * To create array serializer, use overload with [KType] or [ArraySerializer] directly. | ||
| * | ||
| * Caching on JVM platform is disabled for this function, so it may work slower than an overload with [KType]. | ||
| * | ||
| * **Pitfall**: the returned serializer may return incorrect results or throw a [ClassCastException] if it receives | ||
| * a value that's not a valid instance of the [KType], even though the type allows passing such a value. |
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Suggested change
| * a value that's not a valid instance of the [KType], even though the type allows passing such a value. | |
| * a value that's not a valid instance of the [KClass], even though the type allows passing such a value. |
| @@ -103,11 +113,14 @@ public fun serializer( | |||
| * This overload works with full type information, including type arguments and nullability, | |||
| * and is a recommended way to retrieve a serializer. | |||
| * For example, `serializerOrNull<typeOf<List<String?>>>()` returns [KSerializer] that is able | |||
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This line also needs change to serializerOrNull(typeOf<List<String?>>()) while we're here
| @@ -120,12 +133,18 @@ public fun serializerOrNull(type: KType): KSerializer<Any?>? = EmptySerializersM | |||
| * | |||
| * This overload works with full type information, including type arguments and nullability, | |||
| * and is a recommended way to retrieve a serializer. | |||
| * For example, `serializer<typeOf<List<String?>>>()` returns [KSerializer] that is able | |||
| * to serialize and deserialize list of nullable strings — i.e. `ListSerializer(String.serializer().nullable)`. | |||
| * For example, `serializer(typeOf<List<String?>>)` returns [KSerializer] that is able | |||
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Suggested change
| * For example, `serializer(typeOf<List<String?>>)` returns [KSerializer] that is able | |
| * For example, `serializer(typeOf<List<String?>>())` returns [KSerializer] that is able |
| @@ -169,11 +194,14 @@ public fun SerializersModule.serializer( | |||
| * This overload works with full type information, including type arguments and nullability, | |||
| * and is a recommended way to retrieve a serializer. | |||
| * For example, `serializerOrNull<typeOf<List<String?>>>()` returns [KSerializer] that is able | |||
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And here, if you do not mind
sandwwraith
approved these changes
Jun 25, 2025
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Fixes #2948