Lecture Notes: Code Mods and Migration Tools by Matt Chaff

Introduction to Matt Chaff

• Speaker: Matt Chaff
• Location: Just outside of London
• Contributions:
  • Candy S and Feathers JS
  • Migration tools for Kin GS6

Overview of Code Mods

• Purpose of Code Mods:
  • Simplifies repetitive programming tasks
  • Facilitates complex transformations (e.g., library upgrades)

Tools for Code Mods

• JHF (JavaScript Helper Framework):

  • Used for running code mods in JavaScript

• JS Code Shift:

  • Developed by Facebook
  • Utilizes Recast for AST transformations

Understanding AST (Abstract Syntax Tree)

• Definition:
  • An abstract representation of code structure
  • Focuses on the structural content without formatting details

Exploring JavaScript ASTs

• SC Explorer:
  • Online tool for exploring JavaScript ASTs
  • Allows users to write and test code transformations

Sections of SC Explorer

1. Input Section: Paste code to inspect
2. Tree View: Navigate the AST structure
3. Transformation Section: Write transformation functions
4. Output Section: View results of transformations

Example Transformation

• Transforming Candy S5 to Candy S6:
  • Left side: Candy S5 component syntax
  • Right side: Candy S6 component syntax

Transformation Details

• Use of methods like find() to locate expressions
• Properties of components (e.g., view and tag) extracted for transformation
• Replacement process involves creating new class declarations with static getters

Transformation Process

• Determine how the component is used (variable, explorer, component)
• Generate Pascal case for tag names
• Construct new class body and link it to the extended class

Output and Further Resources

• Demonstrated transformations in action
• Links provided for:
  • JS Code Shift
  • SC Explorer
  • Migration tools

Q&A

• Question: How long does it typically take to write a code mod?
  • Answer: Varies based on complexity, generally takes 4-5 hours
  • Saves significant time when dealing with numerous transformations.