mason

name	mason
description	Working with Mason bricks: installing the CLI, creating and consuming bricks, understanding brick structure, Mustache template syntax, hooks, and discovering bricks on BrickHub.
when_to_use	Use when creating, modifying, generating, or debugging Mason bricks and templates. Also use when asked about brick.yaml, __brick__ templates, Mustache syntax, hooks, mason.yaml, or publishing to BrickHub.
allowed-tools	Read Glob Grep Bash

Mason

Mason is a collection of tools that allow developers to create and consume reusable templates called bricks. BrickHub is the registry where bricks are published and discovered.

---

Core Standards

• All template logic belongs in hooks — __brick__/ files use only Mustache tags; no conditional logic lives in template files
• Every brick variable must appear in both brick.yaml and config.json — a missing key in config.json breaks CI generation
• Never edit version.txt, brick.yaml version, or CHANGELOG.md manually — these are owned by release-please
• Hook packages require 100% test coverage — CI enforces this via report_on: "pre_gen.dart" in each *_hooks.yaml workflow
• Use {{{variable}}} (triple braces) when the value must not be HTML-escaped — double braces escape special characters by default

---

CLI Installation

# Activate from pub.dev (recommended)
dart pub global activate mason_cli

# Or via Homebrew
brew tap felangel/mason
brew install mason

Verify the installation:

mason --version

---

Workspace Setup

Initialize Mason in a directory to create a mason.yaml that tracks installed bricks:

mason init

Install all bricks listed in mason.yaml:

mason get

---

Consuming Bricks

Add a brick

# From BrickHub
mason add very_good_core

# From a local path
mason add my_brick --path ./path/to/brick

# From a Git repository
mason add my_brick --git-url https://github.com/org/repo --git-path bricks/my_brick

Generate code from a brick

# Interactive prompts for each variable
mason make very_good_core

# Pass variables inline (used in CI via config.json)
mason make very_good_core -c very_good_core/config.json \
  --on-conflict overwrite -o very_good_core_output

List installed bricks

mason list

---

Brick Structure

<brick>/
  __brick__/      # Mustache template files — the generated output
  hooks/          # pre_gen.dart / post_gen.dart + pubspec.yaml + test/
  brick.yaml      # Metadata and variable definitions
  CHANGELOG.md    # Auto-generated — never edit by hand
  LICENSE
  README.md

brick.yaml

Defines the brick name, version, and all input variables:

name: my_brick
description: A sample brick.
version: 0.1.0+1
environment:
  mason: ">=0.1.0 <0.1.0"
vars:
  project_name:
    type: string
    description: The name of the project.
    default: my_project
    prompt: What is the project name?
  use_flutter:
    type: boolean
    description: Whether to include Flutter dependencies.
    default: true
    prompt: Include Flutter?

Variable Types

Type	Description	Example
string	A primitive string	"my_project"
number	A primitive number	42
boolean	A primitive boolean	true / false
enum	Single choice from a fixed list	["red", "green"] → "red"
array	Multiple choices from a fixed list	["ios", "android"] → ["ios"]
list	Open-ended list of strings	["dart", "python"]

---

Mustache Template Syntax

Templates live in __brick__/ and use Mustache syntax.

Variable interpolation

# Hello {{name}}!

Use triple braces to skip HTML escaping:

{{{raw_html_content}}}

Conditionals

{{#use_flutter}}
  flutter:
    sdk: flutter
{{/use_flutter}}

{{^use_flutter}}
# Pure Dart project
{{/use_flutter}}

Conditionals also work on file paths — wrap the filename in the brick variable to generate the file only when the variable is true:

__brick__/
  {{#create_changelog}}CHANGELOG.md{{/create_changelog}}

Loops

{{#platforms}}
- {{.}}
{{/platforms}}

Built-in Lambdas

Apply case transformations directly in templates or file names:

Lambda	Example output	Shorthand syntax
camelCase	helloWorld	{{name.camelCase()}}
pascalCase	HelloWorld	{{name.pascalCase()}}
snakeCase	hello_world	{{name.snakeCase()}}
paramCase	hello-world	{{name.paramCase()}}
constantCase	HELLO_WORLD	{{name.constantCase()}}
dotCase	hello.world	{{name.dotCase()}}
pathCase	hello/world	{{name.pathCase()}}
sentenceCase	Hello world	{{name.sentenceCase()}}
titleCase	Hello World	{{name.titleCase()}}
lowerCase	hello world	{{name.lowerCase()}}
upperCase	HELLO WORLD	{{name.upperCase()}}

Lambdas apply to file names too:

__brick__/
  {{name.snakeCase()}}.dart

Partials

Reuse template fragments across files using partials. Partial files are prefixed with {{~ }} and included with {{> }}:

__brick__/
  HELLO.md
  {{~ header.md }}
  {{~ footer.md }}

In HELLO.md:

{{> header.md }}
Hello {{name}}!
{{> footer.md }}

---

Hooks

Hooks run Dart code before (pre_gen) or after (post_gen) generation. All conditional logic and derived variable computation belongs here — never in __brick__/ files.

hooks/
  pre_gen.dart
  post_gen.dart
  pubspec.yaml
  lib/
  test/

pre_gen.dart

import 'package:mason/mason.dart';

void run(HookContext context) {
  // Read a variable
  final name = context.vars['project_name'] as String;

  // Compute and inject a derived variable
  context.vars['project_name_pascal'] = name.pascalCase;

  // Log to the user
  context.logger.info('Generating $name...');
}

post_gen.dart

import 'dart:io';
import 'package:mason/mason.dart';

Future<void> run(HookContext context) async {
  final progress = context.logger.progress('Installing packages');
  await Process.run('flutter', ['pub', 'get']);
  progress.complete();
}

Disable hooks during generation with --no-hooks:

mason make my_brick --no-hooks

---

Creating a New Brick

# Scaffold a new brick in the current directory
mason new my_brick

# With a custom description
mason new my_brick --desc "Generates a feature module"

# With hooks scaffolded
mason new my_brick --hooks

# In a specific output directory
mason new my_brick -o ./bricks

---

Discovering Bricks on BrickHub

Search for community bricks at brickhub.dev/search or via the CLI:

mason search <query>

---

Publishing a Brick

# Log in to BrickHub
mason login

# Publish the brick in the current directory
mason publish

---

Anti-Patterns

Anti-Pattern	Problem	Correct Approach
Putting conditional logic in __brick__/ files	Mustache is logic-less; complex conditions become unreadable	Move all logic to pre_gen.dart and inject derived variables
Adding a variable to brick.yaml but not config.json	CI generation fails with a missing key error	Always keep both files in sync
Editing version.txt or CHANGELOG.md by hand	Breaks the automated release-please workflow	Let release-please manage versioning
Using {{variable}} for raw HTML or code with <, >, &	Output gets HTML-escaped	Use {{{variable}}} for unescaped output
Skipping hook tests	CI enforces 100% coverage on hook code	Write tests for every hook code path

---

References

• BrickHub Documentation
• Mason GitHub Repository
• BrickHub Search
• Mustache Manual