Quibble is a JSON diff tool for .NET. You give Quibble two text strings with JSON content and it will tell you what the differences are.
Quibble distinguishes between four kinds of differences:
TypeDiff: e.g.stringvsnumber.ValueDiff: same type but different value, e.g. the stringcatvs the stringdog.ObjectDiff: when two JSON objects have differences in their properties, e.g. the object{ "name": "Quux" }vs the object{ "id": "1c3d" }.ArrayDiff: when two JSON arrays have a different items, e.g. the array[ 1, 2, 3 ]vs the array[ 2, 3, 4 ].
Quibble makes the following assumptions:
- Order of items matters for arrays.
- Order of properties does not matter for objects.
- Different ways of writing the same number do not matter.
Quibble is useful whenever you need to compare two JSON documents to see if and how they're different. Since JSON is pretty much everywhere these days, that's really a basic feature.
Quibble uses JSONPath syntax to point you to the right elements. In JSONPath syntax, $ indicates the root of the document, whereas something like $.books[1].author means "the author property of the second element of the books array".
If you're using xUnit.net to write tests, you may want to check out Quibble.Xunit, an extension to XUnit that does asserts on text strings with JSON content.
open Quibble
Use JsonStrings.diff to get a list of Diff-values that you can map, filter and pattern match as you like.
Use JsonStrings.textDiff to get a list of text descriptions of the differences.
If you read the examples and wonder what $ means, note that Quibble uses JSONPath syntax to point you to differences.
JsonStrings.diff "1" "2"
yields the following list of diffs:
[ Value {
Path = "$";
Left = JsonNumber (1., "1");
Right = JsonNumber (2., "2") } ]
The JsonNumber type contains both the parsed double value of the number and the original text representation from the JSON string. The reason is that there can be several text representations of the same number (e.g. 1.0 and 1 are the same number in JSON). Quibble keeps both in order to compare double values for differences, yet report any differences using the original text representations.
To get a text description of the difference between the JSON numbers 1 and 2:
JsonStrings.textDiff "1" "2"
|> List.head
|> printfn "%s"
prints
Number value difference at $: 1 vs 2.
If you instead compare the JSON numbers 1.0 and 2, you get this:
JsonStrings.textDiff "1.0" "2"
|> List.head
|> printfn "%s"
prints
Number value difference at $: 1.0 vs 2.
The numbers 1 and 1.0 are parsed into the same JSON number, yet Quibble reports the difference using the original text representation.
To make this very explicit:
JsonStrings.diff "1.0" "1"
yields an empty list of diffs:
[]
The reason is that JSON doesn't distinguish between integers and doubles, everything is just a number. Hence 1.0 and 1 are the same number written in different ways.
JsonStrings.diff "123.4" "1.234E2"
also yields an empty list of diffs:
[]
The reason is that 123.4 and 1.234E2 are just different ways of writing the same number.
Quibble uses Ratcliff/Obershelp pattern recognition to describe the differences between arrays. It is based on finding the longest common sub-arrays.
JsonStrings.diff "[ 3 ]" "[ 3, 7 ]"
|> List.head
|> printfn "%s"
yields the following list of diffs:
[ Items ({ Path = "$"
Left = JsonArray [ JsonNumber(3., "3") ]
Right = JsonArray [ JsonNumber(3., "3"); JsonNumber(7., "7") ] },
[ RightOnlyItem (1, JsonNumber(7., "7")) ]
For a text description:
JsonStrings.textDiff "[ 3 ]" "[ 3, 7 ]"
|> List.head
|> printfn "%s"
prints
Array difference at $.
+ [1] (the number 7)
JsonStrings.diff "[ 24, 12 ]" "[ 12, 24 ]"
yields the following list of diffs:
[ Items ({ Path = "$"
Left = JsonArray [ JsonNumber(24., "24"); JsonNumber(12., "12") ]
Right = JsonArray [ JsonNumber(12., "12"); JsonNumber(24., "24") ] },
[ LeftOnlyItem (0, JsonNumber(24., "24"))
RightOnlyItem (1, JsonNumber(24., "24")) ]) ]
Quibble identifies [12] as the longest common sub-array, and treats the leading 24 in the left array and the trailing 24 in the right array as extra elements.
For a text description:
JsonStrings.textDiff "[ 24, 12 ]" "[ 12, 24 ]"
|> List.head
|> printfn "%s"
prints
Array difference at $.
- [0] (the number 24)
+ [1] (the number 24)
The benefits of using longest common sub-array for creating the diff are more apparent for longer arrays that are almost the same.
let str1 = """[{
"title": "Data and Reality",
"author": "William Kent"
}, {
"title": "Thinking Forth",
"author": "Leo Brodie"
}, {
"title": "Programmers at Work",
"author": "Susan Lammers"
}, {
"title": "The Little Schemer",
"authors": [ "Daniel P. Friedman", "Mattias Felleisen" ]
}, {
"title": "Object Design",
"authors": [ "Rebecca Wirfs-Brock", "Alan McKean" ]
}, {
"title": "Domain Modelling made Functional",
"author": "Scott Wlaschin"
}, {
"title": "The Psychology of Computer Programming",
"author": "Gerald M. Weinberg"
}, {
"title": "Exercises in Programming Style",
"author": "Cristina Videira Lopes"
}, {
"title": "Land of Lisp",
"author": "Conrad Barski"
}]"""
let str2 = """[{
"title": "Data and Reality",
"author": "William Kent"
}, {
"title": "Thinking Forth",
"author": "Leo Brodie"
}, {
"title": "Coders at Work",
"author": "Peter Seibel"
}, {
"title": "The Little Schemer",
"authors": [ "Daniel P. Friedman", "Mattias Felleisen" ]
}, {
"title": "Object Design",
"authors": [ "Rebecca Wirfs-Brock", "Alan McKean" ]
}, {
"title": "Domain Modelling made Functional",
"author": "Scott Wlaschin"
}, {
"title": "The Psychology of Computer Programming",
"author": "Gerald M. Weinberg"
}, {
"title": "Turtle Geometry",
"authors": [ "Hal Abelson", "Andrea diSessa" ]
}, {
"title": "Exercises in Programming Style",
"author": "Cristina Videira Lopes"
}, {
"title": "Land of Lisp",
"author": "Conrad Barski"
}]"""
JsonStrings.diff str1 str2
yields the following list of diffs:
[ ArrayDiff ({ Path = "$"; Left = JsonArray [ ... ]; Right = JsonArray [ ... ] },
[ LeftOnlyItem (2, JsonObject [("title", JsonString "Programmers at Work")
("author", JsonString "Susan Lammers")])
RightOnlyItem (2, JsonObject [("title", JsonString "Coders at Work")
("author", JsonString "Peter Seibel")]);
RightOnlyItem (7, JsonObject [("title", JsonString "Turtle Geometry")
("authors", JsonArray [ JsonString "Hal Abelson"; JsonString "Andrea diSessa" ])])]) ]
The most interesting part is the list of item mismatches, which contains the items that are present either in just the left JSON array ("Programmers at work" by Susan Lammers, at index 2) or just in the right JSON array ("Coders at Work" by Peter Seibel, at index 2, and "Turtle Geometry" by Hal Abelson and Andrea diSessa, at index 7).
For a text description:
JsonStrings.diff str1 str2
|> List.head
|> printfn "%s"
prints
Array difference at $.
- [2] (an object)
+ [2] (an object)
+ [7] (an object)
let str1 = """{ "item": "widget", "price": 12.20 }"""
let str2 = """{ "item": "widget", "quantity": 88, "in stock": true }"""
JsonStrings.diff str1 str2
yields the following list of diffs:
[ Properties
({ Path = "$"
Left =
JsonObject
[ ("item", JsonString "widget")
("price", JsonNumber(12.2, "12.20")) ]
Right =
JsonObject
[ ("item", JsonString "widget")
("quantity", JsonNumber(88.0, "88"))
("in stock", JsonTrue) ] },
[ LeftOnlyProperty("price", JsonNumber(12.2, "12.20"))
RightOnlyProperty("quantity", JsonNumber(88.0, "88"))
RightOnlyProperty("in stock", JsonTrue) ]) ]
Quibble treats it as a single difference with three mismatching properties.
For a text description:
let str1 = """{ "item": "widget", "price": 12.20 }"""
let str2 = """{ "item": "widget", "quantity": 88, "in stock": true }"""
JsonStrings.textDiff str1 str2
|> List.head
|> printfn "%s"
prints
Object difference at $.
Left only property: 'price' (number).
Right only properties: 'quantity' (number), 'in stock' (bool).
let str1 = """{ "name": "Maya", "date of birth": "1999-04-23" }"""
let str2 = """{ "name": "Maya", "date of birth": "1999-04-24" }"""
JsonStrings.diff str1 str2
yields the following list of diffs:
[ Value
{ Path = "$['date of birth']"
Left = JsonString "1999-04-23"
Right = JsonString "1999-04-24" } ]
JSONPath handles spaces in property names by using the alternative bracket-and-quotes syntax shown.
For a text description:
let str1 = """{ "name": "Maya", "date of birth": "1999-04-23" }"""
let str2 = """{ "name": "Maya", "date of birth": "1999-04-24" }"""
JsonStrings.textDiff str1 str2
|> List.head
|> printfn "%s"
prints
String value difference at $['date of birth']: 1999-04-23 vs 1999-04-24.
let str1 =
"""{
"books": [{
"title": "Data and Reality",
"author": "William Kent"
}, {
"title": "Thinking Forth",
"author": "Leo Brodie"
}]
}"""
let str2 =
"""{
"books": [{
"title": "Data and Reality",
"author": "William Kent",
"edition": "2nd"
}, {
"title": "Thinking Forth",
"author": "Chuck Moore"
}]
}"""
JsonStrings.diff str1 str2
yields the following list of differences:
[ Properties
({ Path = "$.books[0]"
Left =
JsonObject
[ ("title", JsonString "Data and Reality")
("author", JsonString "William Kent") ]
Right =
JsonObject
[ ("title", JsonString "Data and Reality")
("author", JsonString "William Kent")
("edition", JsonString "2nd") ] },
[ RightOnlyProperty("edition", JsonString "2nd") ])
Value
{ Path = "$.books[1].author"
Left = JsonString "Leo Brodie"
Right = JsonString "Chuck Moore" } ]
For a text description:
let str1 =
"""{
"books": [{
"title": "Data and Reality",
"author": "William Kent"
}, {
"title": "Thinking Forth",
"author": "Leo Brodie"
}]
}"""
let str2 =
"""{
"books": [{
"title": "Data and Reality",
"author": "William Kent",
"edition": "2nd"
}, {
"title": "Thinking Forth",
"author": "Chuck Moore"
}]
}"""
let diffs = JsonStrings.textDiff str1 str2
match diffs with
| [ diff1; diff2 ] ->
printfn "%s" diff1
printfn "%s" diff2
prints
Object difference at $.books[0].
Right only property: 'edition' (string).
String value difference at $.books[1].author: Leo Brodie vs Chuck Moore.
using Quibble.CSharp;
Use JsonStrings.Diff to get a read-only list of Diff-values that you can work with as you like - loop, branch, pattern match etc.
Use JsonStrings.TextDiff to get a read-only list of text descriptions of the differences.
If you read the examples and wonder what $ means, note that Quibble uses JSONPath syntax to point you to differences.
JsonStrings.Diff("1", "2");
yields a list of diffs equivalent to this:
new List<Diff>
{
new ValueDiff(
new DiffPoint("$",
new JsonNumber(1, "1"),
new JsonNumber(2, "2")))
};
For a text description:
var diffs = JsonStrings.TextDiff("1", "2");
Console.WriteLine(diff.Single());
prints
Number value difference at $: 1 vs 2.
If you instead compare the JSON numbers 1.0 and 2, you get this:
var diffs = JsonStrings.TextDiff("1.0", "2");
Console.WriteLine(diff.Single());
prints
Number value difference at $: 1.0 vs 2.
The numbers 1 and 1.0 are parsed into the same JSON number, yet Quibble reports the difference using the original text representation.
To make this very explicit:
JsonStrings.Diff("1.0", "1");
yields an empty list of diffs.
The reason is that JSON doesn't distinguish between integers and doubles, everything is just a number. Hence 1.0 and 1 are the same number written in different ways.
JsonStrings.Diff("123.4", "1.234E2");
also yields an empty list of diffs. The reason is that 123.4 and 1.234E2 are just different ways of writing the same number.
Quibble uses Ratcliff/Obershelp pattern recognition to describe the differences between arrays. It is based on finding the longest common sub-arrays.
JsonStrings.Diff("[ 3 ]", "[ 3, 7 ]");
yields a list of diffs equivalent to this:
new List<Diff>
{
new ArrayDiff(
new DiffPoint("$",
new JsonArray (
new JsonValue []
{
new JsonNumber(3, "3")
}),
new JsonArray (
new JsonValue []
{
new JsonNumber(3, "3"),
new JsonNumber(7, "7")
})),
new ItemMismatch[]
{
new RightOnlyItem(1, new JsonNumber(7, "7")),
})
};
For a text description:
var diffs = JsonStrings.TextDiff("[ 3 ]", "[ 3, 7 ]");
Console.WriteLine(diffs.Single());
prints
Array difference at $.
+ [1] (the number 7)
The most interesting part is the ItemMismatch array, which contains the items that are present either in just the left array ("Programmers at work" by Susan Lammers, at index 2) or just in the right array ("Coders at Work" by Peter Seibel, at index 2, and "Turtle Geometry" by Hal Abelson and Andrea diSessa, at index 7).
JsonStrings.Diff("[ 24, 12 ]", "[ 12, 24 ]");
yields a list of diffs equivalent to this:
new List<Diff>
{
new ArrayDiff(
new DiffPoint("$",
new JsonArray (new JsonValue []
{
new JsonNumber(24, "24"),
new JsonNumber(12, "12")
}),
new JsonArray (new JsonValue []
{
new JsonNumber(12, "12"),
new JsonNumber(24, "24")
})),
new ItemMismatch[]
{
new LeftOnlyItem(0, new JsonNumber(24, "24")),
new RightOnlyItem(1, new JsonNumber(24, "24"))
})
};
For a text description:
var diffs = JsonStrings.TextDiff("[ 24, 12 ]", "[ 12, 24 ]");
Console.WriteLine(diffs.Single());
prints
Array difference at $.
- [0] (the number 24)
+ [1] (the number 24)
The benefits of using longest common sub-array for creating the diff are more apparent for longer arrays that are almost the same.
var str1 = @"[{
""title"": ""Data and Reality"",
""author"": ""William Kent""
}, {
""title"": ""Thinking Forth"",
""author"": ""Leo Brodie""
}, {
""title"": ""Programmers at Work"",
""author"": ""Susan Lammers""
}, {
""title"": ""The Little Schemer"",
""authors"": [ ""Daniel P. Friedman"", ""Matthias Felleisen"" ]
}, {
""title"": ""Object Design"",
""authors"": [ ""Rebecca Wirfs-Brock"", ""Alan McKean"" ]
}, {
""title"": ""Domain Modelling made Functional"",
""author"": ""Scott Wlaschin""
}, {
""title"": ""The Psychology of Computer Programming"",
""author"": ""Gerald M. Weinberg""
}, {
""title"": ""Exercises in Programming Style"",
""author"": ""Cristina Videira Lopes""
}, {
""title"": ""Land of Lisp"",
""author"": ""Conrad Barski""
}]";
var str2 = @"[{
""title"": ""Data and Reality"",
""author"": ""William Kent""
}, {
""title"": ""Thinking Forth"",
""author"": ""Leo Brodie""
}, {
""title"": ""Coders at Work"",
""author"": ""Peter Seibel""
}, {
""title"": ""The Little Schemer"",
""authors"": [ ""Daniel P. Friedman"", ""Matthias Felleisen"" ]
}, {
""title"": ""Object Design"",
""authors"": [ ""Rebecca Wirfs-Brock"", ""Alan McKean"" ]
}, {
""title"": ""Domain Modelling made Functional"",
""author"": ""Scott Wlaschin""
}, {
""title"": ""The Psychology of Computer Programming"",
""author"": ""Gerald M. Weinberg""
}, {
""title"": ""Turtle Geometry"",
""authors"": [ ""Hal Abelson"", ""Andrea diSessa"" ]
}, {
""title"": ""Exercises in Programming Style"",
""author"": ""Cristina Videira Lopes""
}, {
""title"": ""Land of Lisp"",
""author"": ""Conrad Barski""
}]";
var actualDiffs = JsonStrings.Diff(str1, str2);
yields the following list of diffs:
new List<Diff>
{
new ArrayDiff(new DiffPoint("$", new JsonArray(...), new JsonArray(...)),
new ItemMismatch[]
{
new LeftOnlyItem(2,
new JsonObject(
new Dictionary<string, JsonValue>
{
{"title", new JsonString("Programmers at Work")},
{"author", new JsonString("Susan Lammers")}
})),
new RightOnlyItem(2,
new JsonObject(
new Dictionary<string, JsonValue>
{
{"title", new JsonString("Coders at Work")},
{"author", new JsonString("Peter Seibel")}
})),
new RightOnlyItem(7,
new JsonObject(
new Dictionary<string, JsonValue>
{
{"title", new JsonString("Turtle Geometry")},
{
"authors",
new JsonArray(new JsonValue[] {
new JsonString("Hal Abelson"),
new JsonString("Andrea diSessa")
})
}
}))
})
};
The most interesting part is the ItemMismatch array, which contains the items that are present either in just the left array ("Programmers at work" by Susan Lammers, at index 2) or just in the right array ("Coders at Work" by Peter Seibel, at index 2, and "Turtle Geometry" by Hal Abelson and Andrea diSessa, at index 7).
For a text description:
var diffs = JsonStrings.TextDiff(str1, str2);
Console.WriteLine(diffs.Single());
prints
Array difference at $.
- [2] (an object)
+ [2] (an object)
+ [7] (an object)
var str1 = @"{ ""item"": ""widget"", ""price"": 12.20 }";
var str2 = @"{ ""item"": ""widget"", ""quantity"": 88, ""in stock"": true }";
JsonStrings.Diff(str1, str2);
yields a list of diffs equivalent to this:
new List<Diff>
{
new ObjectDiff(
new DiffPoint("$",
new JsonObject(
new Dictionary<string, JsonValue>
{
{ "item", new JsonString("widget") },
{ "price", new JsonNumber(12.20, "12.20") }
}),
new JsonObject(
new Dictionary<string, JsonValue>
{
{ "item", new JsonString("widget") },
{ "quantity", new JsonNumber(88, "88") },
{ "in stock", JsonTrue.Instance }
})),
new List<PropertyMismatch>
{
new LeftOnlyProperty("price", new JsonNumber(12.20, "12.20")),
new RightOnlyProperty("quantity", new JsonNumber(88, "88")),
new RightOnlyProperty("in stock", JsonTrue.Instance)
})
};
Quibble treats it as a single difference with three mismatching properties.
For a text description:
var str1 = @"{ ""item"": ""widget"", ""price"": 12.20 }";
var str2 = @"{ ""item"": ""widget"", ""quantity"": 88, ""in stock"": true }";
var diffs = JsonStrings.TextDiff(str1, str2);
Console.WriteLine(diffs.Single());
prints
Object difference at $.
Left only property: 'price' (number).
Right only properties: 'quantity' (number), 'in stock' (bool).
var str1 = @"{ ""name"": ""Maya"", ""date of birth"": ""1999-04-23"" }";
var str2 = @"{ ""name"": ""Maya"", ""date of birth"": ""1999-04-24"" }";
JsonStrings.Diff(str1, str2);
yields a list of diffs equivalent to this:
new List<Diff>
{
new ValueDiff(
new DiffPoint("$['date of birth']",
new JsonString("1999-04-23"),
new JsonString("1999-04-24")))
};
JSONPath handles spaces in property names by using the alternative bracket-and-quotes syntax shown.
For a text description:
var str1 = @"{ ""name"": ""Maya"", ""date of birth"": ""1999-04-23"" }";
var str2 = @"{ ""name"": ""Maya"", ""date of birth"": ""1999-04-24"" }";
var diffs = JsonStrings.TextDiff(str1, str2);
Console.WriteLine(diffs.Single());
prints
String value difference at $['date of birth']: 1999-04-23 vs 1999-04-24.
var str1 = @"{
""books"": [{
""title"": ""Data and Reality"",
""author"": ""William Kent""
}, {
""title"": ""Thinking Forth"",
""author"": ""Leo Brodie""
}]
}";
var str2 = @"{
""books"": [{
""title"": ""Data and Reality"",
""author"": ""William Kent"",
""edition"": ""2nd""
}, {
""title"": ""Thinking Forth"",
""author"": ""Chuck Moore""
}]
}";
JsonStrings.Diff(str1, str2);
yields a list of diffs equivalent to this:
new List<Diff>
{
new ObjectDiff(
new DiffPoint("$.books[0]",
new JsonObject(
new Dictionary<string, JsonValue>
{
{ "title", new JsonString("Data and Reality") },
{ "author", new JsonString("William Kent") }
}),
new JsonObject(
new Dictionary<string, JsonValue>
{
{ "title", new JsonString("Data and Reality") },
{ "author", new JsonString("William Kent") },
{ "edition", new JsonString("2nd") }
})),
new List<PropertyMismatch>
{
new RightOnlyProperty("edition", new JsonString("2nd"))
}),
new ValueDiff(
new DiffPoint("$.books[1].author",
new JsonString("Leo Brodie"),
new JsonString("Chuck Moore")))
};
For a text description:
var str1 = @"{
""books"": [{
""title"": ""Data and Reality"",
""author"": ""William Kent""
}, {
""title"": ""Thinking Forth"",
""author"": ""Leo Brodie""
}]
}";
var str2 = @"{
""books"": [{
""title"": ""Data and Reality"",
""author"": ""William Kent"",
""edition"": ""2nd""
}, {
""title"": ""Thinking Forth"",
""author"": ""Chuck Moore""
}]
}";
var diffs = JsonStrings.TextDiff(str1, str2);
foreach (var diff in diffs)
{
Console.WriteLine(diff);
}
prints
Object difference at $.books[0].
Right only property: 'edition' (string).
String value difference at $.books[1].author: Leo Brodie vs Chuck Moore.