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https://github.com/espadrine/json-diff
Compute the difference between two JSON-serializable Ruby objects.
https://github.com/espadrine/json-diff
Last synced: 10 days ago
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Compute the difference between two JSON-serializable Ruby objects.
- Host: GitHub
- URL: https://github.com/espadrine/json-diff
- Owner: espadrine
- License: mit
- Created: 2016-06-11T21:31:42.000Z (over 8 years ago)
- Default Branch: master
- Last Pushed: 2020-09-22T14:06:12.000Z (about 4 years ago)
- Last Synced: 2024-04-26T15:04:59.814Z (7 months ago)
- Language: Ruby
- Size: 18.6 KB
- Stars: 75
- Watchers: 7
- Forks: 9
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# `json-diff`
*Take two Ruby objects that can be serialized to JSON. Output an array of operations (additions, deletions, moves) that would convert the first one to the second one.*
```bash
gem install json-diff # Or `gem 'json-diff'` in your Gemfile.
```
```ruby
require 'json-diff'
JsonDiff.diff(1, 2)
#> [{'op' => 'replace', 'path' => '', 'value' => 2}]
```
Outputs [RFC6902][]. Look at [hana][] for a JSON patch algorithm that can use this output.
[RFC6902]: http://www.rfc-editor.org/rfc/rfc6902.txt
[hana]: https://github.com/tenderlove/hana
# Options
- `include_was`: include a `was` field in remove and replace operations, to show the old value. Allows computing reverse operations without the source JSON.
- `moves`\*: include move operations. Set it to false to remove clutter.
- `additions`\*: include add operations. Set it to false to remove clutter.
- `original_indices`\*: array indices are those from the source array (for `from` fields, or `path` fields on remove operations) or the target array (for other `path` fields). It eases manual checking of differences.
- `similarity`: procedure taking (before, after) objects. Returns a probability between 0 and 1 of how likely `after` is a modification of `before`, or nil if you wish to fall back to the default computation.
\* Changing this option prevents the use of the output for JSON patching.
You can also install its associated program to use this on the command line:
```bash
gem install json-diff # On Linux, you may need to use sudo
json-diff before.json after.json
```
# Heart
- Recursive similarity computation between any two Ruby values.
- For arrays, match elements above a certain level of similarity pairwise, and treat them as a move.
- Matching happens highest-similarity first.
- The creation of move operations is generated by detecting rings in the list of moved elements (eg, A → B → C → A).
Pros:
- For lists which are not necessarily ordered, this approach yields far better results than LCS.
- Move operations require no custom code to match elements.
Cons:
- This approach's quality is heavily reliant on how good the similarity algorithm is. Empirically, it yields sensible output. It can be improved by a user-defined procedure.
- There is a computational overhead to the default similarity computation that scales with the total number of entities in the structure.
# Comparisons
[HashDiff](https://github.com/liufengyun/hashdiff) — LCS, no move operation.
```ruby
require "json-diff"
JsonDiff.diff([1, 2, 3, 4, 5], [6, 4, 3, 2])
# [{'op' => 'remove', 'path' => '/4'},
# {'op' => 'remove', 'path' => '/0'},
# {'op' => 'move', 'from' => '/0', 'path' => '/2'},
# {'op' => 'move', 'from' => '/1', 'path' => '/0'},
# {'op' => 'add', 'path' => '/0', 'value' => 6}]
require "hashdiff"
HashDiff.diff([1, 2, 3, 4, 5], [6, 4, 3, 2])
# [["-", "[0]", 1],
# ["+", "[0]", 6],
# ["+", "[1]", 4],
# ["+", "[2]", 3],
# ["-", "[6]", 5],
# ["-", "[5]", 4],
# ["-", "[4]", 3]]
```
[jsondiff](https://github.com/francois2metz/jsondiff) — no similitude, no LCS.
```ruby
require "json-diff"
JsonDiff.diff(
[{'code' => "ABW", 'name' => "Abbey Wood"}, {'code' => "KGX", 'name' => "Kings Cross"}],
[{'code' => "KGX", 'name' => "Kings Cross"}, {'code' => "ABW", 'name' => "Abbey Wood"}]
)
# [{'op' => 'move', 'from' => '/0', 'path' => '/1'}]
require "jsondiff"
JsonDiff.generate(
[{'code' => "ABW", 'name' => "Abbey Wood"}, {'code' => "KGX", 'name' => "Kings Cross"}],
[{'code' => "KGX", 'name' => "Kings Cross"}, {'code' => "ABW", 'name' => "Abbey Wood"}]
)
# [{:op => :replace, :path => '/0/code', :value => 'KGX'},
# {:op => :replace, :path => '/0/name', :value => 'Kings Cross'},
# {:op => :replace, :path => '/1/code', :value => 'ABW'},
# {:op => :replace, :path => '/1/name', :value => 'Abbey Wood'}]
```
# Plans & Bugs
Roughly ordered by priority.
- Support LCS as an option. (The default will remain what yields the best results, regardless of the time it takes.)
- Support specifying a depth for similarity computation.
- Character-wise substring add and remove operations.
- SVG output.
---
See the LICENSE file for licensing information.