@travetto/compiler

Travetto Compiler

The framework, while using typescript, has need of some extended functionality. The additional functionality is

• Supports on-the-fly compilation, nothing needs to be compiled ahead of time
• Enhanced AST transformations, and transformer registration
  • All AST transformations are single-file based, and runs without access to the TypeChecker
• Intelligent caching of source files to minimize recompilation
• Support for watching sources files:
  • Detecting changes to files
  • Detecting changes to specific classes
  • Detecting changes to specific methods within classes
• Allows for hot-reloading of classes during development
  • Utilizes es2015 Proxys to allow for swapping out implementation at runtime

Additionally, there is support for common AST transformation patterns to facilitate all the transformers used throughout the framework. Functionality includes:

• getDecoratorIdent(d: ts.Decorator): ts.Identifier Gets the name of the decorator function
• findAnyDecorator(node: ts.Node, patterns: { [key: string]: Set<string> }, state: State): ts.Decorator | undefined Attempts to find any matching decorators as defined in patterns
• addImport(file: ts.SourceFile, imports: Import[]) Will add an import to the existing source file
• fromLiteral(val: any) Converts a literal value to the corresponding AST nodes
• extendObjectLiteral(addTo: object, lit?: ts.ObjectLiteralExpression)
  Extends an AST Node via a literal value, generally used to emulate Object.assign in the AST
• getPrimaryArgument<T = ts.Node>(node: ts.CallExpression | ts.Decorator | undefined): T | undefined Retrieves the first argument of CallExpression or Decorator
• getObjectValue(node: ts.ObjectLiteralExpression | undefined, key: string) Extracts the literal value from an AST node if possible
• importingVisitor Provides a transformer visitor that collects imports, and adds them to the source file as needed
• importIfExternal<T extends State>(typeNode: ts.TypeNode, state: State) Will import a reference if the type is not defined within the file
• buildImportAliasMap(pathToType) Will generate an import lookup to be used for simple type resolution

Transformations are defined by support/transformation.<name>.ts as the filename. The schema for a transformer is

  export class CustomerTransformer {
    priority: 1, // Lower is higher priority
    phase: 'before'|'after', // The phase as defined by Typescript's AST processing
    transformer: (context: ts.TransformationContext) => {
       return (file: ts.SourceFile) => {
         ... modify source file ...
         return file;
       }
    }
  }