Serialization

JSON

FullPath is serialized as a JSON string by FullPathJsonConverter. The converter is declared on the type, so there is nothing to register:

FullPath output = FullPath.GetTempPath() / "output";

// A FullPath is written as a JSON string
string json = JsonSerializer.Serialize(output);
Assert.Equal(JsonSerializer.Serialize(output.Value), json);
Assert.Equal(output, JsonSerializer.Deserialize<FullPath>(json));

// A relative path is resolved against the current directory, and an empty string gives the empty path
Assert.Equal(FullPath.CurrentDirectory() / "output", JsonSerializer.Deserialize<FullPath>("\"output\""));
Assert.True(JsonSerializer.Deserialize<FullPath>("\"\"").IsEmpty);

• null and an empty string give the empty path, and the empty path is written as an empty string.
• A relative path is resolved against the current directory when the document is read. To resolve the paths of a configuration file against its own folder, read them as strings and combine them with the folder of the file.
• A string that is not a valid path throws a JsonException. The original exception is its InnerException; the message does not contain the path.

Source generator, trimming and NativeAOT

The converter works with the System.Text.Json source generator. Declare a FullPath property like any other:

[JsonSourceGenerationOptions(RespectNullableAnnotations = true, RespectRequiredConstructorParameters = true)]
[JsonSerializable(typeof(Configuration))]
internal sealed partial class AppJsonContext : JsonSerializerContext;

internal sealed record Configuration(FullPath OutputPath);

The package is trimmable and compatible with NativeAOT: it does not use reflection, and its native interop is generated at compile time.