asset_url_for() returns None in flask cookie cutter (flask-webpack)

Question

Im new to webpack. Im using flask-cookie-cutter which in turn uses Flask-Webpack
Im having issues in that App wont find my images in development.
Images are in assets/img folder Ive tried using {{ asset_url_for('img/img_name.png') }} and various variations of it - and it just returns none.
Ive tried the usual flask way of {{ url_for('static', filename='img/img_name.png') }}
But I cant seem to access them.

const path = require('path');
const webpack = require('webpack');

/*
 * Webpack Plugins
 */
const ManifestRevisionPlugin = require('manifest-revision-webpack-plugin');
const MiniCssExtractPlugin = require('mini-css-extract-plugin');

// take debug mode from the environment
const debug = (process.env.NODE_ENV !== 'production');

// Development asset host (webpack dev server)
const publicHost = debug ? 'http://0.0.0.0:2992' : '';

const rootAssetPath = path.join(__dirname, 'assets');

module.exports = {
  // configuration
  context: __dirname,
  entry: {
    main_js: './assets/js/main',
    main_css: [
      path.join(__dirname, 'node_modules', 'materialize-css', 'dist', 'css', 'materialize.css'),
      path.join(__dirname, 'assets', 'css', 'style.css'),
    ],
  },
  output: {
    path: path.join(__dirname, 'dsi_website', 'static', 'build'),
    publicPath: `${publicHost}/static/build/`,
    filename: '[name].[hash].js',
    chunkFilename: '[id].[hash].js',
  },
  resolve: {
    extensions: ['.js', '.jsx', '.css'],
  },
  devtool: 'source-map',
  devServer: {
    headers: { 'Access-Control-Allow-Origin': '*' },
  },
  module: {
    rules: [
      {
        test: /\.less$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              hmr: debug,
            },
          },
          'css-loader!less-loader',
        ],
      },
      {
        test: /\.css$/,
        use: [
          {
            loader: MiniCssExtractPlugin.loader,
            options: {
              hmr: debug,
            },
          },
          'css-loader',
        ],
      },
      { 
        test: /\.html$/, 
        loader: 'raw-loader' 
      },
      { 
        test: /\.woff(2)?(\?v=[0-9]\.[0-9]\.[0-9])?$/, 
        loader: 'url-loader', 
        options: { 
          limit: 10000, 
          mimetype: 'application/font-woff' 
        } 
      },
      {
        test: /\.(ttf|eot|svg|png|jpe?g|gif|ico)(\?.*)?$/i,
        loader: `file-loader?context=${rootAssetPath}&name=[path][name].[hash].[ext]`
      },
      { 
        test: /\.js$/, 
        exclude: /node_modules/, 
        loader: 'babel-loader', 
        query: { 
          presets: ['env'], 
          cacheDirectory: true 
        } 
      },
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({ filename: '[name].[hash].css', }),
    new webpack.ProvidePlugin({ $: 'jquery', jQuery: 'jquery' }),
    new ManifestRevisionPlugin(path.join(__dirname, 'dsi_website', 'webpack', 'manifest.json'), {
      rootAssetPath,
      ignorePaths: ['/js', '/css'],
    }),
  ].concat(debug ? [] : [
    // production webpack plugins go here
    new webpack.DefinePlugin({
      'process.env': {
        NODE_ENV: JSON.stringify('production'),
      }
    }),
  ]),
};

Answer 1

I was the same problem with flask-cookie-cutter and solve it by update/upgrade npm and add extensionsRegex: /\.(jpe?g|png|gif|svg)$/i at down file: webpack.config.js like this:

ManifestRevisionPlugin(path.join(__dirname, '<your app>', 'webpack', 'manifest.json'), {
      rootAssetPath,
      ignorePaths: ['/js', '/css'],
      extensionsRegex: /\.(jpe?g|png|gif|svg)$/i
    }),

source solution. Proper call to show image in temaplate:

{{ asset_url_for('img/img_name.png') }}

after that i check startup screen and i see that all my images load properly

[WEBPACK]                                    _/assets/img/image_name.20aed528d50316c91ffedb5ba47b8c74.jpg  18.9 KiB            [emitted]