intern3-to-intern4-partial.js

module.exports = function(file, api) {
  // Alias the jscodeshift API.
  var j = api.jscodeshift;
  // Parse JS code into AST.
  var root = j(file.source);
  
  root.find(j.ExpressionStatement).forEach(function(p) {
    // Only change the registerSuite method.
    if (p.value.expression.callee && 
        p.value.expression.callee.name === "registerSuite") {
      let obj = p.value.expression.arguments[0];
      let props = p.value.expression.arguments[0].properties;

      // Get the suite name.
      const name = j.literal(props[0].value.value);

      // Remove first element from props, because it's the name of the suite.
      props.shift();
      let new_props = [],
          tests = [];

      // This are the reserved methods from Intern 3 
      // and their equivalents in Intern 4.
      const reservedMethods = {
        "setup": "before",
        "teardown": "after"
      }

      props.forEach(function(m) {
        // Get the old name and turn it into a valid function name.
        const m_name =  m.key.type === "Identifier" ? m.key :
                        j.identifier('"' + m.key.value + '"');

        // Get the actual function expression.
        const m_exp = m.value;
        const method = j.property("init", m_name, m_exp);
        method.method = true;

        let found = false;
        for(const reservedMethod in reservedMethods){
          if (m_name.name === reservedMethod) {
            method.key.name = reservedMethods[reservedMethod];
            new_props.push(method);
            found = true;
          }
        }

        if(!found) tests.push(method)
      });

      const testsId = j.identifier("tests")
      const testsObj = j.objectExpression(tests)
      const testsProperty = j.property("init", testsId, testsObj);
      new_props.push(testsProperty);

      // Generate Intern 4 methods object.
      const methods = j.objectExpression(new_props);

      // Do the actual replacing.
      p.value.expression.arguments[0] = name;
      p.value.expression.arguments.push(methods);
    }
  });

  return root.toSource();
};