PICK — Regex Builder for VS Code

PICK is a VS Code extension that helps you turn a natural-language description into a precise regular expression through a short interactive workflow.

Instead of guessing a single regex, PICK generates multiple candidate patterns and asks you to classify example strings to quickly narrow down the correct regex. It uses automata-based analysis (via @gruhn/regex-utils) for formally correct set operations and randexp for example generation.

Key ideas:

• Generate a set of candidate regexes from an LLM (3–5 candidates).
• Iterate: show two example strings and ask which one is "IN" (matches) or "OUT" (doesn't match). The controller uses these judgments to eliminate candidates.
• Continue until you accept an example for one regex (we select it), or all candidates are eliminated (then we tell you none matched).
• The extension ensures examples are unique and tries to maximize information gained from each judgment.
• Session Management: Refine your prompt while preserving your existing classifications, or start fresh with a new prompt.

Quick start

Note: When you first use PICK, VS Code will show a permission popup asking to allow the extension to use "Language Models" (or "Chat Models"). You need to grant this permission for the extension to generate regex candidates.

1. In VS Code, open the PICK Regex Builder view in the Activity Bar (left sidebar).
2. Enter a short description of the regex you want (e.g., "IPv4 octet, from 0–255").
3. Classify example strings until PICK converges to a final regex, or the candidates are exhausted.
4. Refine Your Prompt: If you want to iterate on your prompt without losing your work, click "Refine Prompt" to generate new candidates while preserving your existing classifications.
5. Start Fresh: If you want to begin a completely new regex task, click "Start Fresh" to clear all state and begin anew.

Developer workflow / Try it locally

Requirements

• Node.js: v20.18.1 or newer (the extension uses vsce/undici which require Node 20+)

Check your Node version with:

node -v

If Node is older than v20.x, use nvm or your OS package manager to install Node 20:

# Using nvm
nvm install 20
nvm use 20

• Build (TypeScript):
  • npm run compile
• Lint:
  • npm run lint
• Test:
  • npm test
• Run the extension in development: press F5 from this repository with VS Code extension host.

Try locally using the CLI:

npm ci
npm run compile
npm run package:vsix
If you edit `package.json` and it adds/removes dependencies, make sure to update the lock file with:

```bash
# Ensure you're on Node v20 (see above)
npm install
git add package-lock.json
git commit -m "chore: update lockfile"
git push

If npm ci fails with a message like "package.json and package-lock.json are not in sync" or missing modules, run npm install to regenerate the lockfile and commit it. CI uses npm ci to install from lockfile for deterministic builds.

Use "Extensions: Install from VSIX..." in VS Code to install the generated .vsix

Session Management
------------------
PICK now supports session management to help you iteratively refine your regex without losing your work:

- **Refine Prompt**: Click "Refine Prompt" during the classification phase or after getting a final result. This allows you to:
  - Update your natural language description
  - Generate new candidate regexes based on the refined prompt
  - **Preserve all your existing word classifications** (Accept/Reject/Unsure)
  - Apply those classifications to the new candidates automatically
  - Continue from where you left off with better candidates

- **Start Fresh**: Click "Start Fresh" to completely reset the session:
  - Clears all candidates and classifications
  - Returns to the initial prompt screen
  - Use this when you want to work on a completely different regex task

This two-level reset system allows you to iterate efficiently on your regex without repetitive work, while still providing a clean slate when needed.

Configuration
-------------
Settings are under `pick`:
- `pick.eliminationThreshold` — number of negative votes required to eliminate a candidate (default: 2)
- `pick.llm.vendor` — LLM vendor to use for candidate generation (default: `copilot`)
- `pick.llm.family` — LLM model family to prefer (default: `gpt-4o`)

Troubleshooting
---------------
If you encounter issues with the extension, check the logs for detailed information:

1. Open the Output panel in VS Code (View → Output, or Ctrl+Shift+U / Cmd+Shift+U)
2. In the dropdown at the top right of the Output panel, select "PICK Regex Builder"
3. The logs will show detailed information about extension operations, LLM requests, and any errors

The logs include timestamps and are categorized by severity (INFO, WARN, ERROR) to help with debugging.

Publishing (release process)
 We use GitHub Actions to build (CI) and publish the extension.

Local tag helper script
-----------------------
You can create and push the tag matching your package.json version using the included utility script:

```bash
# Create a tag based on the package version and push it
npm run release:tag

# For additional options
# --dry-run: show commands without executing
# --force: delete and recreate the tag if it already exists
# --no-push: create tag locally but do not push
# --message "Custom tag message": set a custom tag message

Notes

License

MIT