Philiprehberger.ConfigDiff

Structured diff for JSON configuration files — detect added, removed, changed, and unchanged keys.

Installation

dotnet add package Philiprehberger.ConfigDiff

Usage

using Philiprehberger.ConfigDiff;

var jsonA = """
{
  "Logging": { "Level": "Warning" },
  "ConnectionStrings": { "Default": "Server=old" },
  "FeatureFlag": false
}
""";

var jsonB = """
{
  "Logging": { "Level": "Information" },
  "ConnectionStrings": { "Default": "Server=old" },
  "NewSetting": "hello"
}
""";

ConfigDiffResult diff = ConfigComparer.Compare(jsonA, jsonB);

foreach (var key in diff.Added)
    Console.WriteLine($"+ {key}");

foreach (var key in diff.Removed)
    Console.WriteLine($"- {key}");

foreach (var change in diff.Changed)
    Console.WriteLine($"~ {change.Path}: '{change.OldValue}' -> '{change.NewValue}'");

// Output:
// + NewSetting
// - FeatureFlag
// ~ Logging.Level: 'Warning' -> 'Information'

Compare files

var diff = ConfigComparer.CompareFiles("appsettings.json", "appsettings.Production.json");

Compare streams

using var streamA = File.OpenRead("appsettings.json");
using var streamB = File.OpenRead("appsettings.Production.json");
var diff = ConfigComparer.Compare(streamA, streamB);

Ignore paths

Use ignorePaths to exclude specific keys from the comparison. Supports exact matches and wildcard prefix matches with .*:

var diff = ConfigComparer.Compare(jsonA, jsonB, ignorePaths: new[]
{
    "Logging.*",           // ignore everything under Logging
    "ConnectionStrings.*"  // ignore everything under ConnectionStrings
});

// Only NewSetting and FeatureFlag will appear in the result

Rich change entries

Changed entries include both the old and new values via the ConfigChange record:

foreach (var change in diff.Changed)
{
    Console.WriteLine($"{change.Path}: {change.OldValue} -> {change.NewValue}");
}

API

ConfigComparer

Method	Description
Compare(string jsonA, string jsonB, IEnumerable<string>? ignorePaths = null)	Diff two JSON strings
CompareFiles(string pathA, string pathB, IEnumerable<string>? ignorePaths = null)	Read files from disk and diff them
Compare(Stream streamA, Stream streamB, IEnumerable<string>? ignorePaths = null)	Read streams and diff them

ConfigDiffResult

Property	Type	Description
Added	IReadOnlyList<string>	Keys present in B but not in A
Removed	IReadOnlyList<string>	Keys present in A but not in B
Changed	IReadOnlyList<ConfigChange>	Keys present in both with different values
Unchanged	IReadOnlyList<string>	Keys with identical values

ConfigChange

Property	Type	Description
Path	string	Dot-notation key path
OldValue	string?	Value in A
NewValue	string?	Value in B

Development

dotnet build src/Philiprehberger.ConfigDiff.csproj --configuration Release

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License

MIT