Memory error with crawl mode

[astrotim]

I am getting a "JavaScript heap out of memory" error when running a build with crawl: true. Here is the console output

<--- Last few GCs --->

[88328:0x103800000]   371328 ms: Mark-sweep 1402.1 (2063.0) -> 1402.0 (2052.5) MB, 125.9 / 0.0 ms  (+ 0.0 ms in 0 steps since start of marking, biggest step 0.0 ms, walltime since start of marking 127 ms) last resort 
[88328:0x103800000]   371463 ms: Mark-sweep 1402.0 (2052.5) -> 1401.8 (2052.0) MB, 134.4 / 0.0 ms  last resort 


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x1c73bc09bbd9 <JS Object>
    1: /* anonymous */ [.../node_modules/static-site-generator-webpack-plugin/index.js:88] [pc=0x502f8d5fb66](this=0x2690e5c8a1e1 <JS Global Object>,key=0xf0700a8dc39 <Very long string[45664]>)
    2: arguments adaptor frame: 3->1
    3: map [native array.js:~832] [pc=0x502f91c16c7](this=0x395e0fd11431 <JS Array[1]>,bd=0x395e0fd11451 <JS Function (SharedFunctionI...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
 1: node::Abort() [/Users/xxx/.nvm/versions/node/v8.2.1/bin/node]
...

If I disable crawl mode, the build works, but obviously I don't get all my static pages generated.

Node 8.2.1
webpack 2.6.1
static-site-generator-webpack-plugin 3.4.1

The app works normally when I build it as a purely client app using webpack-dev-server.

Is there any way to debug why this is causing the memory error?

---

This is my full Webpack config

const path = require('path');
const webpack = require('webpack');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const StaticSiteGeneratorPlugin = require('static-site-generator-webpack-plugin');

let plugins = [
  new ExtractTextPlugin('style.css'),
  new StaticSiteGeneratorPlugin({
    crawl: true,
    paths: ['/']
  }),
  new CopyWebpackPlugin([
    {
      from: path.resolve(__dirname, 'src', 'favicon.ico'),
      to: path.resolve(__dirname, 'dist')
    },
    {
      from: path.resolve(__dirname, 'fonts'),
      to: path.resolve(__dirname, 'dist', 'fonts')
    }
  ]),
  new webpack.DefinePlugin({
    'process.env': {
      NODE_ENV: JSON.stringify('production')
    }
  }),
  new webpack.optimize.UglifyJsPlugin()
];

if (process.env.ANALYZE_WEBPACK) {
  const BundleAnalyzerPlugin = require('webpack-bundle-analyzer')
    .BundleAnalyzerPlugin;

  plugins.push(
    new BundleAnalyzerPlugin({
      openAnalyzer: false
    })
  );
}

module.exports = {
  entry: {
    bundle: path.resolve(__dirname, 'src')
  },

  output: {
    path: path.resolve(__dirname, 'dist'),
    filename: '[name].js',
    libraryTarget: 'umd'
  },

  plugins: plugins,

  // exclude
  externals: {
    'babel-standalone': 'babel-standalone'
  },

  module: {
    rules: [
      {
        test: /\.js$/,
        include: [path.resolve(__dirname, 'src')],
        use: {
          loader: 'babel-loader',
          options: {
            presets: ['react', 'es2015']
          }
        }
      },
      {
        test: /\.(css|scss)$/,
        loader: ExtractTextPlugin.extract({
          fallback: 'style-loader',
          use: [
            {
              loader: 'css-loader',
              options: {
                modules: true,
                camelCase: true,
                localIdentName: '[name]__[local]--[hash:base64:5]'
              }
            },
            {
              loader: 'postcss-loader',
              options: {
                plugins: [require('autoprefixer')]
              }
            },
            {
              loader: 'sass-loader'
            }
          ]
        })
      }
    ]
  }
};

[astrotim]

I've narrowed this down to an issue with some markdown. I am using a package called marsky to compile markdown into a React tree, but this compilation makes the build hang when I have crawl: true.

The function is

const getMarkup = markdown => {
  if (!markdown) return null;
  console.log('getMarkup', markdown);
  const compile = marksy({
    createElement,
    elements: {}
  });
  return compile(markdown).tree;
};

// invoked as 
{getMarkup(someMarkdown)}

I can see the function call being logged infinitely in the console in crawl mode, but it's fine otherwise.