JsonCompleter

A Ruby gem that converts partial JSON strings into valid JSON with high-performance incremental parsing. Efficiently processes streaming JSON with O(n) complexity for new data by maintaining parsing state between chunks. Handles truncated primitives, missing values, and unclosed structures without reprocessing previously parsed data.

Add this line to your application's Gemfile:

gem 'json_completer'

And then execute:

bundle install

Or install it yourself as:

gem install json_completer

Complete partial JSON strings in one call:

require 'json_completer'

# Complete truncated JSON
JsonCompleter.complete('{"name": "John", "age":')
# => '{"name": "John", "age": null}'

# Handle incomplete strings
JsonCompleter.complete('{"message": "Hello wo')
# => '{"message": "Hello wo"}'

# Fix unclosed structures
JsonCompleter.complete('[1, 2, {"key": "value"')
# => '[1, 2, {"key": "value"}]'

For streaming scenarios where JSON arrives in chunks. Each call processes only new data (O(n) complexity) by maintaining parsing state, making it highly efficient for large streaming responses:

completer = JsonCompleter.new

# Process first chunk
result1 = completer.complete('{"users": [{"name": "')
# => '{"users": [{"name": ""}]}'

# Process additional data
result2 = completer.complete('{"users": [{"name": "Alice"}')
# => '{"users": [{"name": "Alice"}]}'

# Final complete JSON
result3 = completer.complete('{"users": [{"name": "Alice"}, {"name": "Bob"}]}')
# => '{"users": [{"name": "Alice"}, {"name": "Bob"}]}'

• Zero reprocessing: Maintains parsing state to avoid reparsing previously processed data
• Linear complexity: Each chunk processed in O(n) time where n = new data size, not total size
• Memory efficient: Uses token-based accumulation with minimal state overhead
• Context preservation: Tracks nested structures without full document analysis

• High-performance streaming JSON: Process large JSON responses efficiently as data arrives over network connections
• Truncated API responses: Complete JSON that was cut off due to size limits
• Log parsing: Handle incomplete JSON entries in log files

1. Fork the repository
2. Create your feature branch (git checkout -b my-new-feature)
3. Make your changes and add tests
4. Run the test suite (bundle exec rspec)
5. Commit your changes (git commit -am 'Add some feature')
6. Push to the branch (git push origin my-new-feature)
7. Create a new Pull Request

This gem is available as open source under the terms of the MIT License.