tarunkoyalwar / nestle

Match and Extract Nested groups (ex: graphql) using regex with Nestle

Nestle

A simple and easy to use wrapper around regex.Regexp that allows parsing nested objected like brackets,parenthesis etc . The syntax to validate and match a nested group is [{:nested:}] this syntax or match group will validate and match balanced curly brackets.

Why ??

There may be lot of cases where this can be used but nestle is primarily developed with a use case to extract embedded graphql queries from js files which traditionally is not easy and may not be possible due to nested object fields Ex me { id address {street location }}. However this can easily be matched and extracted using nestle .

How does this work ??

Implementaion of nestle is simple it uses 2 regex instances one for regex before say { (Prematch group) and another instance for regex after } (PostMatch group) .Indexes of these two groups are obtained using regexp.Regexp.FindAllStringIndex and continuity and whether the parenthesis are balanced is validated using a simple expression evaluation algorithm which uses stack

Example/Usecase

Extract embedded graphql queries from javascript files

cat js-file.js | nestle -regex '(query|mutation)\s+[a-zA-Z]+[0-9]*[a-zA-Z]+(\([^(\(|\))]+\))*\s*[{:nested:}]'

Above is 100% working example to extract entire graphql query . A sample graphql text file is located at graphql.txt

Disclaimer

1. Nestle Only supports regex that have :nested: syntax since it is explicitly designed for this purposes .

2. Nestle currently does not support normal/other/simple regex since there are better options available.

3. Case where regex query only matches parenthesis ex: [(:nested:)] is discouraged and blacklisted

Installation

• Install from source

go install -v github.com/tarunKoyalwar/nestle/cmd/nestle@latest

• Install from Releases

Usage

Using nestle with syntax [:nested:] . is simple which can be better understood using below example

Example

• Objective : extract user data user {xxx} from below graphql query

query me{
    me {
        id
        username
        user {
            address {
                street
                city
            }
            contact {
                email
                phone
            }
        }
    }
}

to extract user {xxx} including all data between them with parenthesis use regex

(user)\s+[{:nested:}]

and that's it . Here nested group is denoted using [ start_char : nested : end_char ]

Other examples are available in nestle_test.go file and a sample file is available at graphql.txt

Run below command for help

nestle -h

Support

Do start the repo if you liked the project to keeep motivated and create interesting projects

nestle's Issues

error in your give command

'(query|mutation)\s+[a-zA-Z]+[0-9][a-zA-Z]+(([^(\(|\))]+))\s*[{:nested:}]'

A Wrapper around regexp.Regexp that supports Nested Symbols/brackets
Use syntax [(:nested:)] for nested groups