Lave generates invalid JS

[vedantroy]

Example:

const path = require("path");
const fs = require("fs");
const pdfjs = require("pdfjs-dist/legacy/build/pdf.js");
const lave = require("lave");
const { generate } = require("escodegen");

async function go() {
    const pdf = fs.readFileSync(path.join(__dirname, "sample.pdf"));
    const docTask = pdfjs.getDocument(pdf);
    const doc = await docTask.promise;
    const firstPage = await doc.getPage(1);
    const viewport = firstPage.getViewport();

    const proto = Object.getPrototypeOf(viewport);
    const classCode = lave(proto, { generate, format: "module" });
    const DIR = `tests/generated`;
    fs.mkdirSync(DIR, { recursive: true });
    if (!fs.existsSync(DIR)) {
        fs.mkdirSync(DIR, { recursive: true });
    }
    fs.writeFileSync(path.join(DIR, "mock_viewport.js"), classCode);
}
go();

will generate invalid JS.

Specifically, we get (error on last 2 lines):

var a = {
    'constructor': function PageViewport(_ref2) {
    var viewBox = _ref2.viewBox,
        scale = _ref2.scale,
        rotation = _ref2.rotation,
        _ref2$offsetX = _ref2.offsetX,
        offsetX = _ref2$offsetX === void 0 ? 0 : _ref2$offsetX,
        _ref2$offsetY = _ref2.offsetY,
        offsetY = _ref2$offsetY === void 0 ? 0 : _ref2$offsetY,
        _ref2$dontFlip = _ref2.dontFlip,
        dontFlip = _ref2$dontFlip === void 0 ? false : _ref2$dontFlip;

    _classCallCheck(this, PageViewport);

    this.viewBox = viewBox;
    this.scale = scale;
    this.rotation = rotation;
    this.offsetX = offsetX;
    this.offsetY = offsetY;
    var centerX = (viewBox[2] + viewBox[0]) / 2;
    var centerY = (viewBox[3] + viewBox[1]) / 2;
    var rotateA, rotateB, rotateC, rotateD;
    rotation %= 360;

    if (rotation < 0) {
      rotation += 360;
    }

    switch (rotation) {
      case 180:
        rotateA = -1;
        rotateB = 0;
        rotateC = 0;
        rotateD = 1;
        break;

      case 90:
        rotateA = 0;
        rotateB = 1;
        rotateC = 1;
        rotateD = 0;
        break;

      case 270:
        rotateA = 0;
        rotateB = -1;
        rotateC = -1;
        rotateD = 0;
        break;

      case 0:
        rotateA = 1;
        rotateB = 0;
        rotateC = 0;
        rotateD = -1;
        break;

      default:
        throw new Error("PageViewport: Invalid rotation, must be a multiple of 90 degrees.");
    }

    if (dontFlip) {
      rotateC = -rotateC;
      rotateD = -rotateD;
    }

    var offsetCanvasX, offsetCanvasY;
    var width, height;

    if (rotateA === 0) {
      offsetCanvasX = Math.abs(centerY - viewBox[1]) * scale + offsetX;
      offsetCanvasY = Math.abs(centerX - viewBox[0]) * scale + offsetY;
      width = Math.abs(viewBox[3] - viewBox[1]) * scale;
      height = Math.abs(viewBox[2] - viewBox[0]) * scale;
    } else {
      offsetCanvasX = Math.abs(centerX - viewBox[0]) * scale + offsetX;
      offsetCanvasY = Math.abs(centerY - viewBox[1]) * scale + offsetY;
      width = Math.abs(viewBox[2] - viewBox[0]) * scale;
      height = Math.abs(viewBox[3] - viewBox[1]) * scale;
    }

    this.transform = [rotateA * scale, rotateB * scale, rotateC * scale, rotateD * scale, offsetCanvasX - rotateA * scale * centerX - rotateC * scale * centerY, offsetCanvasY - rotateB * scale * centerX - rotateD * scale * centerY];
    this.width = width;
    this.height = height;
  },
    'clone': function clone() {
      var _ref3 = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {},
          _ref3$scale = _ref3.scale,
          scale = _ref3$scale === void 0 ? this.scale : _ref3$scale,
          _ref3$rotation = _ref3.rotation,
          rotation = _ref3$rotation === void 0 ? this.rotation : _ref3$rotation,
          _ref3$offsetX = _ref3.offsetX,
          offsetX = _ref3$offsetX === void 0 ? this.offsetX : _ref3$offsetX,
          _ref3$offsetY = _ref3.offsetY,
          offsetY = _ref3$offsetY === void 0 ? this.offsetY : _ref3$offsetY,
          _ref3$dontFlip = _ref3.dontFlip,
          dontFlip = _ref3$dontFlip === void 0 ? false : _ref3$dontFlip;

      return new PageViewport({
        viewBox: this.viewBox.slice(),
        scale: scale,
        rotation: rotation,
        offsetX: offsetX,
        offsetY: offsetY,
        dontFlip: dontFlip
      });
    },
    'convertToViewportPoint': function convertToViewportPoint(x, y) {
      return _util.Util.applyTransform([x, y], this.transform);
    },
    'convertToViewportRectangle': function convertToViewportRectangle(rect) {
      var topLeft = _util.Util.applyTransform([rect[0], rect[1]], this.transform);

      var bottomRight = _util.Util.applyTransform([rect[2], rect[3]], this.transform);

      return [topLeft[0], topLeft[1], bottomRight[0], bottomRight[1]];
    },
    'convertToPdfPoint': function convertToPdfPoint(x, y) {
      return _util.Util.applyInverseTransform([x, y], this.transform);
    }
};
function PageViewport(_ref2) {
    var viewBox = _ref2.viewBox,
        scale = _ref2.scale,
        rotation = _ref2.rotation,
        _ref2$offsetX = _ref2.offsetX,
        offsetX = _ref2$offsetX === void 0 ? 0 : _ref2$offsetX,
        _ref2$offsetY = _ref2.offsetY,
        offsetY = _ref2$offsetY === void 0 ? 0 : _ref2$offsetY,
        _ref2$dontFlip = _ref2.dontFlip,
        dontFlip = _ref2$dontFlip === void 0 ? false : _ref2$dontFlip;

    _classCallCheck(this, PageViewport);

    this.viewBox = viewBox;
    this.scale = scale;
    this.rotation = rotation;
    this.offsetX = offsetX;
    this.offsetY = offsetY;
    var centerX = (viewBox[2] + viewBox[0]) / 2;
    var centerY = (viewBox[3] + viewBox[1]) / 2;
    var rotateA, rotateB, rotateC, rotateD;
    rotation %= 360;

    if (rotation < 0) {
      rotation += 360;
    }

    switch (rotation) {
      case 180:
        rotateA = -1;
        rotateB = 0;
        rotateC = 0;
        rotateD = 1;
        break;

      case 90:
        rotateA = 0;
        rotateB = 1;
        rotateC = 1;
        rotateD = 0;
        break;

      case 270:
        rotateA = 0;
        rotateB = -1;
        rotateC = -1;
        rotateD = 0;
        break;

      case 0:
        rotateA = 1;
        rotateB = 0;
        rotateC = 0;
        rotateD = -1;
        break;

      default:
        throw new Error("PageViewport: Invalid rotation, must be a multiple of 90 degrees.");
    }

    if (dontFlip) {
      rotateC = -rotateC;
      rotateD = -rotateD;
    }

    var offsetCanvasX, offsetCanvasY;
    var width, height;

    if (rotateA === 0) {
      offsetCanvasX = Math.abs(centerY - viewBox[1]) * scale + offsetX;
      offsetCanvasY = Math.abs(centerX - viewBox[0]) * scale + offsetY;
      width = Math.abs(viewBox[3] - viewBox[1]) * scale;
      height = Math.abs(viewBox[2] - viewBox[0]) * scale;
    } else {
      offsetCanvasX = Math.abs(centerX - viewBox[0]) * scale + offsetX;
      offsetCanvasY = Math.abs(centerY - viewBox[1]) * scale + offsetY;
      width = Math.abs(viewBox[2] - viewBox[0]) * scale;
      height = Math.abs(viewBox[3] - viewBox[1]) * scale;
    }

    this.transform = [rotateA * scale, rotateB * scale, rotateC * scale, rotateD * scale, offsetCanvasX - rotateA * scale * centerX - rotateC * scale * centerY, offsetCanvasY - rotateB * scale * centerX - rotateD * scale * centerY];
    this.width = width;
    this.height = height;
  }.prototype = a;
export default a;