flow like the river

BACK_BACK/node_modules/parcel-bundler/lib/packagers/SourceMapPackager.js

@@ -0,0 +1,47 @@
+"use strict";
+
+var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");
+
+var _asyncToGenerator2 = _interopRequireDefault(require("@babel/runtime/helpers/asyncToGenerator"));
+
+const path = require('path');
+
+const Packager = require('./Packager');
+
+const SourceMap = require('../SourceMap');
+
+class SourceMapPackager extends Packager {
+  start() {
+    var _this = this;
+
+    return (0, _asyncToGenerator2.default)(function* () {
+      _this.sourceMap = new SourceMap();
+    })();
+  }
+
+  addAsset(asset) {
+    var _this2 = this;
+
+    return (0, _asyncToGenerator2.default)(function* () {
+      let offsets = _this2.bundle.parentBundle.getOffset(asset);
+
+      if (asset.sourceMaps[asset.type]) {
+        yield _this2.sourceMap.addMap(asset.sourceMaps[asset.type], offsets[0], offsets[1]);
+      }
+    })();
+  }
+
+  end() {
+    var _superprop_getEnd = () => super.end,
+        _this3 = this;
+
+    return (0, _asyncToGenerator2.default)(function* () {
+      let file = path.basename(_this3.bundle.parentBundle.name);
+      yield _this3.write(_this3.sourceMap.stringify(file, path.relative(_this3.options.outDir, _this3.options.rootDir)));
+      yield _superprop_getEnd().call(_this3);
+    })();
+  }
+
+}
+
+module.exports = SourceMapPackager;