lark-parser/lark

testing/debugging grammar interactively ?

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#149 opened on May 22, 2018

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Description

I am thinking something along the lines of https://omrelli.ug/nearley-playground/ that provides an interactive feedback to the user creating a grammar, via examples or other way. The nicest tool I know is about regular expressions only : https://regex101.com/

Is there something like that for parser grammars ? where we could just add lark syntax?

I am not used to write parser grammars, and I am currently doing this in a python interpreter. The raw python error messages can be quite cryptic for a newcomer. Any idea ? Am I missing an obvious tool here ?

Contributor guide

Tech stack
python
Domain
developer experiencetooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
needs investigation
Prerequisites
basic knowledge of Lark grammarunderstanding of parsing concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The issue requests an interactive grammar debugging tool similar to regex101.com. To implement, one could explore using Lark's Python API to parse example inputs and display errors visually. A web interface could be built using Flask or a simple JavaScript frontend. Key challenges include providing meaningful error messages and real time feedback. Consider referencing existing Lark playground projects or building a new one with a split pane layout showing grammar, input, and parse tree/output.