Add the message in BabelLoaderError's stack trace

[jennings]

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

When a BabelLoaderError is thrown on Node 8.x, the message is not included in the stack property. When webpack wraps the error in a ModuleBuildError, the message is lost from webpack's output:

ERROR in ./entry.js
Module build failed: Error
    at transpile (/Users/stephen/t/node_modules/babel-loader/lib/index.js:64:13)
    at Object.module.exports (/Users/stephen/t/node_modules/babel-loader/lib/index.js:174:20)

What is the new behavior?

The BabelLoaderError's message is included in the stack property, so even after wrapping in a ModuleBuildError, the error message and the code where the error occurred are visible.

ERROR in ./entry.js
Module build failed: /Users/stephen/t/entry.js: Reference to undeclared variable "foo"

> 1 | foo()
    | ^
  2 |
Error
    at transpile (/Users/stephen/t/node_modules/babel-loader/lib/index.js:64:13)
    at Object.module.exports (/Users/stephen/t/node_modules/babel-loader/lib/index.js:174:20)

Does this PR introduce a breaking change?

• Yes
• No

Other information:

I had first thought this was a webpack issue, but they suggested this was something the loader should change.

I think the behavior of Error.captureStackTrace may have changed between Node versions, because this behavior appeared when I upgraded from Node 6.x to 8.x. Perhaps the old behavior was to not read the message property until stack was read, and the new behavior is to read message immediately? I have not had time to verify this, though, this is just speculation.

This is the webpack.config.js I was using to create the error messages above (entry.js simply contains the text foo()):

var path = require('path')

module.exports = {
  entry: path.join(__dirname, 'entry.js'),

  output: {
    filename: 'output.js'
  },

  module: {
    rules: [
      {
        test: /\.js$/,
        use: {
          loader: 'babel-loader',
          options: {
            plugins: ['babel-plugin-undeclared-variables-check']
          }
        }
      }
    ]
  }
}

[danez]

Thanks. I think this is because of this issue: https://bugs.chromium.org/p/v8/issues/detail?id=5962 So v8 started formating the stack sync when calling captureStackTrace which accesses this.message, but we are setting it after calling captureStackTrace.

This will be fixed in some upcoming node version, but to be safe we can merge this.