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A JSON patch extension for merging arrays and objects
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README.md

each; a JSON patch extension for merging arrays and objects

JSON patch (RFC 6902 specs; tutorial) is a method for modifying JSON data structures. I like that JSON patch is more regular than JSON merge patch (RFC 7386 specs; tutorial), but it's a bit limited for merging arrays and objects together. This repo describes an extension of a JSON patch with a member called each, which offers capabilities for merging arrays and objects. JSON patches that are extended with each can be translated to traditional JSON patches. Below is a description of how each works, while you can find a PHP implementation of it in the repo.

In-a-nutshell

If each is true, and...

  • value is an array, then the operation is applied to the target path for each element of the value
  • value is an object, then the operation is applied to each member of the target path for each corresponding member of the value

In both cases, the operation is applied non-recursively, i.e., it is applied to the children of the value and target path, but not to any grandchildren.

How each works with arrays

Imagine we'd like to patch this data structure:

["s1", "s2", "s3"]

Traditional JSON patch

If we apply this traditional JSON patch:

{
  "value": ["t1", "t2"],
  "path": "/-",
  "op": "add"
}

Then the result would be

["s1", "s2", "s3", ["t1", "t2"]]

JSON patch extended with each

However, if we would apply this extended JSON patch

{
  "value": ["t1", "t2"],
  "path": "/-",
  "op": "add",
  "each": true
}

Then the patch operation is applied for each element of value, which translates to a traditional JSON patch as follows

[{
  "value": "t1",
  "path": "/-",
  "op": "add"
},{
  "value": "t2",
  "path": "/-",
  "op": "add"
}]

And the result would be

["s1", "s2", "s3", "t1", "t2"]

Using each with a numbered index

If providing a numbered index, then the value array is inserted at the target path in whole. For example, if we apply this extended JSON patch

{
  "value": ["t1", "t2"],
  "path": "/1",
  "op": "add",
  "each": true
}

It translates to traditional JSON patching as follows

[{
  "value": "t1",
  "path": "/1",
  "op": "add"
},{
  "value": "t2",
  "path": "/2",
  "op": "add"
}]

And the result would be

["s1", "t1", "t2", "s2", "s3"]

How each works with objects

Imagine we'd like to patch this data structure:

{"p1": "s1", "p2": "s2"}

Traditional JSON patch

If we apply this traditional JSON patch:

{
  "value": {"q1": "t1", "q2": "t2"},
  "path": "",
  "op": "add"
}

Then the result would be

{"q1": "t1", "q2": "t2"}

JSON patch extended with each

However, if we would apply this extended JSON patch

{
  "value": {"q1": "t1", "q2": "t2"},
  "path": "",
  "op": "add",
  "each": true
}

Then the patch operation is applied for each property of value, which translates to a traditional JSON patch as follows

[{
  "value": "t1",
  "path": "/q1",
  "op": "add"
},{
  "value": "t2",
  "path": "/q2",
  "op": "add"
}]

And the result would be

{"p1": "s1", "p2": "s2", "q1": "t1", "q2": "t2"}

Final Words

  • The PHP implementation can be found in each_implementation.php. It provides a function that converts an JSON patch extended with each to a traditional JSON patch. The extension is illustrated by converting some JSON patches and applying them using the json-diff library.
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