Webpack Plugin's Module Size

[Pirororor]

I am currently trying to monitor a specific module's output bundle size that is in an asset.

I tried creating a webpack plugin to simply log down all the modules' sizes:

apply(compiler) {
  compiler.hooks.done.tapAsync('ModuleSizePlugin', (stats, callback) => {
        const moduleBreakdown = {};
        const compilation = stats.compilation.chunks.forEach(chunk => {
          const chunkInfo = {
            id: chunk.id,
            name: chunk.name,
            modules: [],
          };
  
          chunk.getModules().forEach(module => {
            const moduleInfo = {
              resource: module.resource || '',
              name: module.name || '',
              module: this.getModuleSize(module),
              chunk: {
                id: chunk.id,
                name: chunk.name,
              },
            };
            chunkInfo.modules.push(moduleInfo);
            if (!moduleBreakdown[module.resource]) {
              moduleBreakdown[module.resource] = { info: [] };
            }
            moduleBreakdown[module.resource].info.push(moduleInfo);
          });
        });    
  
       console.log(moduleInfo)
  }
}


getModuleSize(module) {
  const ret = {};
  if (module._source && module._source.size) {
    ret['_sourceSize'] = module._source.size();
  }
  if (module.size) {
    ret['size'] = module.size();
  }
  return ret;
}

1. I that there are _source.size, size and a sizes.javascript fields, but I realise that not all modules have all 3. When does each appear?
2. It seems that size does not correspond to the size in the asset. (e.g when the asset only contains only 1 module, seems that the module's size is larger than the asset's size.) When is the size field in the module calculated?

[alexander-akait]

It seems that size does not correspond to the size in the asset. (e.g when the asset only contains only 1 module, seems that the module's size is larger than the asset's size.) When is the size field in the module calculated?

For assets there is sizes.asset

Code - https://github.com/webpack/webpack/blob/main/lib/asset/AssetGenerator.js#L591

Same for any modules

[Pirororor]

It seems that size does not correspond to the size in the asset. (e.g when the asset only contains only 1 module, seems that the module's size is larger than the asset's size.) When is the size field in the module calculated?

For assets there is sizes.asset

Code - https://github.com/webpack/webpack/blob/main/lib/asset/AssetGenerator.js#L591

Same for any modules

I see. However, if the output bundle asset consists of more than 1 module, is there a way to see the breakdown on how much each bundle occupied?

[alexander-akait]

The module has https://github.com/webpack/webpack/blob/main/lib/Module.js#L876C2-L876C16

[Pirororor]

Thanks a lot for your help.

It seems that size does not correspond to the size in the asset. (e.g when the asset only contains only 1 module, seems that the module's size is larger than the asset's size.) When is the size field in the module calculated?

This is the issue I face when using module's size field.

After researching more, seems that module's size field is pre-minification and pre-bundling, and the size directly corresponds to the source's size. Since I am lookign for how much each module's size takes out in the output bundle, seems like webpack-bundle-analyzer's way of manually estimating how much size each module uses up in a bundle is the way to go.