mixpanel-report.js

// Babel plugin to parse the AST and find where mixpanel events are called.
// This is used to generate the `mixpanel-report.json` file.
// https://github.com/thejameskyle/babel-handbook/blob/master/translations/en/plugin-handbook.md
const fs = require('fs');

const _ = require('lodash');


const OUTPUT_PATH = './build-external/mixpanel-report.json';

const events = [];

// Extracts params from `trackMixpanelEvent` calls.
// Tries to parse out strings used as params, but some can only be determined at runtime.
function extractProps(props) {
  return _.reduce(props, (r, p) => {
    const key = _.get(p, 'key.name');
    if (p.value) {
      const value = p.value.type === 'StringLiteral' ? p.value.value : `<variable: ${p.value.name}>`;
      r[key] = value;
    }
    return r;
  }, {});
}

const findMixpanel = {
  CallExpression(path, { name, parent }) {
    path.traverse({
      Identifier(child) {
        if (child.node.name === 'trackMixpanelEvent') {
          let mixpanelEventParams;
          const mixpanelEventName = _.get(child.parent, 'arguments[0].value');
          const params = _.get(child.parent, 'arguments[1].properties');
          const description = _.get(child.parent, 'arguments[2].value');

          if (params) {
            mixpanelEventParams = extractProps(params);
          }

          const d = {
            file: _.get(path.hub, ['file', 'opts', 'sourceFileName']),
            mixpanelEventName,
            loc: path.node.loc,
            mixpanelEventParams,
            functionName: name,
            parentClass: parent,
            description: description || null,
          };

          events.push(d);
        }
      }
    });
  }
};

const classMethods = {
  ClassMethod(path, { name }) {
    path.traverse(findMixpanel, { name: _.get(path.node, ['key', 'name']), parent: name });
  }
};

module.exports = function parse() {
  return {
    visitor: {
      FunctionDeclaration(path) {
        // Search in functions
        path.traverse(findMixpanel, { name: _.get(path.node, ['id', 'name']) });
      },
      ClassDeclaration(path) {
        // Search in class methods
        path.traverse(classMethods, { name: _.get(path.node, ['id', 'name']) });
      },
    },
    post() {
      fs.writeFileSync(OUTPUT_PATH, JSON.stringify(events, null, 2));
    }
  };
};