Can't export when enumerable is "!0"

Input File:

Object.defineProperty(exports, 'a', {
  enumerable: true,
  value: 'a'
});

Object.defineProperty(exports, 'b', {
  enumerable: !0,
  value: 'b'
});

Expected Result: ["a", "b"]
Actual Result: ["a"]

We can get this case when we use uglifyjs to minify our source code.

The Error is occured in https://github.com/guybedford/cjs-module-lexer/blob/a96e7b52b99d39fee25d69f356905161d14a15ed/lexer.js#L370

Here is a simple solution:

          if (source.startsWith('true', pos)) {
            pos += 4;
          } else if (source.startsWith('!0', pos)) {
            pos += 2;
          } else {
            break;
          }

Start at lexer.js around line 370, where enumerable values are recognized during CommonJS export analysis. Reproduce the provided input containing enumerable: true and enumerable: !0, then verify that both "a" and "b" are reported as named exports.