typhonjs-istanbul-instrument-jspm/dist/instrumentIstanbulSystem.js

Provides a NPM module to add Istanbul instrumentation to JSPM / SystemJS by replacing the System.translate hook.

'use strict';

Object.defineProperty(exports, "__esModule", {
   value: true
});
exports.default = instrumentIstanbulSystem;

var _istanbulLibInstrument = require('istanbul-lib-instrument');

var _istanbulLibInstrument2 = _interopRequireDefault(_istanbulLibInstrument);

function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }

// Good enough ES6 module detection regex.
// Format detections not designed to be accurate, but to handle the 99% use case.
var s_ESM_REGEX = /(^\s*|[}\);\n]\s*)(import\s*(['"]|(\*\s+as\s+)?[^"'\(\)\n;]+\s*from\s*['"]|\{)|export\s+\*\s+from\s+["']|export\s* (\{|default|function|class|var|const|let|async\s+function))/;

/**
 * Instruments JSPM / SystemJS replacing the `System.translate` hook adding Istanbul instrumentation of loaded source
 * code before deferring the instrumented source for translation. The instrumentation process occurs on the original
 * source code and supports ES5 and ES Modules (ES6+).
 *
 * @param {object}   System - An instance of SystemJS.
 *
 * @param {RegExp}   sourceFilePathRegex - A regex which defines which source files are instrumented; default excludes
 *                                         any sources with file paths that includes `jspm_packages`.
 */
function instrumentIstanbulSystem(System) {
   var sourceFilePathRegex = arguments.length <= 1 || arguments[1] === undefined ? /^((?!jspm_packages).)*$/ : arguments[1];

   /* istanbul ignore if */
   if (typeof System.translate !== 'function') {
      throw new TypeError("instrumentIstanbulSystem - 'System' is not an instance of the SystemJS API.");
   }

   /* istanbul ignore if */
   if (!(sourceFilePathRegex instanceof RegExp)) {
      throw new TypeError("instrumentIstanbulSystem - 'sourceFilePathRegex' is not an instance of RexExp.");
   }

   // Coverage variable created by Istanbul and stored in global variables.
   var coverageVariable = Object.keys(global).filter(function (key) {
      return key.startsWith('$$cov_');
   })[0];

   /* istanbul ignore if */
   if (typeof coverageVariable === 'undefined') {
      throw new TypeError('instrumentIstanbulSystem - Istanbul coverage variable could not be located in global variables.');
   }

   // ES5 instrumenter
   var instrumenter = _istanbulLibInstrument2.default.createInstrumenter({ coverageVariable: coverageVariable });

   // ES6 / ES Modules instrumenter
   var instrumenterESM = _istanbulLibInstrument2.default.createInstrumenter({ coverageVariable: coverageVariable, esModules: true });

   // Store the original `System.translate` hook.
   var systemTranslate = System.translate;

   // Override SystemJS translate hook to instrument original sources with Istanbul.
   System.translate = function (load) {
      var filePath = load.address.substr(System.baseURL.length);

      // Use `sourceFilePathRegex` to test file path for source instrumentation.
      if (sourceFilePathRegex.test(filePath)) {
         /* istanbul ignore next */
         try {
            // If a source file passes the ES6 / ES Module regex test then use the ESM instrumenter.
            if (s_ESM_REGEX.test(load.source) || load.metadata.format === 'esm') {
               load.source = instrumenterESM.instrumentSync(load.source, filePath);
            } else {
               load.source = instrumenter.instrumentSync(load.source, filePath);
            }
         } catch (err) {
            var newErr = new Error('Unable to instrument \'' + load.name + '\' for Istanbul:\n\t' + err.message);
            newErr.stack = 'Unable to instrument \'' + load.name + '\' for istanbul:\n\t' + err.stack;
            newErr.originalErr = err.originalErr || err;
            throw newErr;
         }
      }

      // Defer to the original `System.translate` hook.
      return systemTranslate.call(System, load);
   };
}