feat: Add conditional question support with `when` clause in brick.yaml

[mehuldadlani]

Hey there! 👋

So I've been working with mason bricks and noticed something that could really improve the user experience. Right now, when you create a brick with multiple options (like different auth methods), users get bombarded with irrelevant questions.

The Problem

Imagine this scenario - you're creating a Flutter app and you select "no_auth" as your authentication method, but then mason still asks you:

• "Do you want to enable Google Sign-In with Firebase?"
• "Do you want to enable Apple Sign-In with Firebase?"

Like... what? 😅 That doesn't make any sense! If I chose no auth, why am I getting Firebase questions?

What I'm Proposing

Add a simple when clause to brick.yaml variables so we can conditionally show questions based on previous answers. Something like this:

vars:
  auth_method:
    type: enum
    values: [firebase, custom_jwt, no_auth]
    default: firebase
    prompt: Which authentication method do you want to use?

  firebase_google:
    type: boolean
    default: true
    prompt: Do you want to enable Google Sign-In with Firebase?
    when: auth_method == firebase  # Only show if firebase is selected

  firebase_apple:
    type: boolean
    default: true
    prompt: Do you want to enable Apple Sign-In with Firebase?
    when: auth_method == firebase  # Only show if firebase is selected

Why This Matters

Current Flow (Confusing):

? Which authentication method do you want to use? no_auth
? Do you want to enable Google Sign-In with Firebase? (Y/n) 🤔
? Do you want to enable Apple Sign-In with Firebase? (Y/n) ��
*

With when clause (Clean):

What Needs to Be Done

Parser Stuff:

• Make brick.yaml understand when conditions
• Add validation for condition syntax
• Support basic operators like ==, !=, in, not in

Real-World Example

I'm building a Flutter Riverpod starter brick, and when someone selects "no_auth", they still get Firebase questions. It's super confusing! This feature would fix that instantly.

---

TL;DR: Add when clauses to brick.yaml so questions only show when they're relevant. Makes mason way more user-friendly! 🚀

[mehuldadlani]

When Clause Feature - Need Your Input

🎯 The Problem

Hey! I've been working with Mason bricks and noticed this annoying issue where complex bricks keep asking irrelevant questions. Like when you choose Firebase auth, it still asks about JWT secrets and stuff that doesn't apply.

💡 My Solution Idea

I thought adding a when clause would be super helpful. Here's what I'm thinking:

# brick.yaml
vars:
  auth_method:
    type: enum
    description: "Which authentication method do you want to use?"
    values: [firebase, custom_jwt, no_auth]
    default: firebase
  
  firebase_google:
    type: boolean
    description: "Do you want to enable Google Sign-In with Firebase?"
    default: true
    when: "auth_method == firebase"  # Only shows up if you picked firebase
  
  custom_jwt_secret:
    type: string
    description: "What is your JWT secret key?"
    when: "auth_method == custom_jwt"  # Only shows up if you picked custom_jwt

✅ What I've Built

I've actually implemented the whole thing! It includes:

• Added a when field to the data model
• Built a condition evaluator that handles ==, !=, in, not in
• Integrated it into the CLI so it skips irrelevant prompts
• Updated the JSON schema so IDEs can validate it
• Made a demo brick to show how it works
• Wrote up documentation

⚠️ The Catch

Here's the tricky part - the implementation needs Dart SDK 3.8.0+ because json_serializable generates code with null-aware elements (?instance.field). This breaks backward compatibility.

The error looks like this:

This requires the 'null-aware-elements' language feature to be enabled.
line 29: 'repository': ?instance.repository,

🤔 What Should I Do?

I'm not sure how to handle the SDK compatibility issue. Here are my options:

Option 1: Just go with Dart 3.8.0+

• ✅ Clean implementation using modern Dart features
• ✅ Works perfectly with the existing architecture
• ❌ Breaks backward compatibility

Option 2: Build it differently

• Create a separate system for when clauses
• Use manual JSON parsing instead of json_serializable
• Keep the existing classes unchanged
• ❌ More complex, no IDE validation

Option 3: Wait for your thoughts

• Hold off until you give me direction
• Work on something else instead

📋 What's Ready

I've got these files ready to go:

1. packages/mason/lib/src/brick_yaml.dart - Added when field
2. packages/mason/lib/src/condition_evaluator.dart - New evaluator
3. packages/mason_cli/lib/src/commands/make.dart - CLI integration
4. extensions/vscode/schema/brick.yaml.schema.json - JSON schema
5. bricks/when_demo/ - Demo brick
6. WHEN_CLAUSE_FEATURE.md - Documentation

What do you think? Should I:

1. Go ahead with the Dart 3.8.0+ requirement?
2. Try the alternative approach without json_serializable?
3. Wait for your guidance on the best approach?
4. Focus on something else entirely?

The when clause would make complex brick configurations way more user-friendly, but I want to make sure it fits with your vision for Mason's compatibility requirements.

📝 Next Steps

I can raise a PR with all the implementation so you can review the code directly. The feature is fully functional and ready for your review. Would you like me to:

1. Submit a PR with the complete implementation for your review?
2. Wait for your guidance on the SDK compatibility approach first?
3. Create a draft PR so you can see the code and provide feedback?

Let me know what you'd prefer - I'm happy to submit the PR whenever you're ready to review it!

[mehuldadlani]

Hey @felangel, any updates on this?

[felangel]

Hey @felangel, any updates on this?

Sorry haven’t had time to look yet! Should be able to take a closer look today or tomorrow, thanks for the contributions and for you patience!