Recovery

The RecoveryModule provides handling for a JsonException thrown while JsonSettings parses the file during loading. On failure, one of the following RecoveryAction values decides what happens:

RecoveryAction	Behavior
Throw	Throw a JsonSettingsRecoveryException with the real exception as its inner exception.
RenameAndLoadDefault	Append the version and a collision counter to the faulty file's name, load defaults, and save them to disk. e.g. myfile.json versioned 1.0.0.5 is renamed to myfile.1.0.0.5-0.json, and a fresh default myfile.json is written. (A non-versioned settings class uses just the counter, e.g. myfile.0.json.)
LoadDefault	Load default settings without touching the existing file until the next save.
LoadDefaultAndSave	Load default settings and save them to disk immediately.

All recovery properties and methods are suited for inheritance, so extending is easy.

Attaching it

Use the WithRecovery fluent extension (from Nucs.JsonSettings.Modulation.Recovery):

using Nucs.JsonSettings;
using Nucs.JsonSettings.Autosave;
using Nucs.JsonSettings.Modulation.Recovery;

public class RecoverableSettings : JsonSettings {
    public override string FileName { get; set; } = "somename.json";
    public virtual string AutoProperty { get; set; } = "Hi";

    public RecoverableSettings() { }
    public RecoverableSettings(string fileName) : base(fileName) { }
}

var settings = JsonSettings.Configure<RecoverableSettings>("abouttofail.jsn")
                           .WithRecovery(RecoveryAction.RenameAndLoadDefault)
                           .LoadNow()
                           .EnableAutosave();

settings.AutoProperty = "Hello"; //Boom! saves.

// ...later the file on disk gets corrupted (edited by hand, truncated, etc.)

// Loading again does not throw: the corrupt file is renamed aside and defaults are loaded.
settings = JsonSettings.Configure<RecoverableSettings>("abouttofail.jsn")
                       .WithRecovery(RecoveryAction.RenameAndLoadDefault)
                       .LoadNow()
                       .EnableAutosave();

Console.WriteLine(settings.AutoProperty); // "Hi" — the default, because the corrupt file was
                                          // renamed to abouttofail.<version>.jsn and a fresh
                                          // default abouttofail.jsn was written.

Note

Recovery handles parse failures. If instead you want to react to a schema/version change in a file that still parses, use Versioning. The two compose: versioning runs on a successful parse, recovery catches the parse itself failing.