Compilation Hooks

The Compilation module is used by the Compiler to create new compilations (or builds). A compilation instance has access to all modules and their dependencies (most of which are circular references). It is the literal compilation of all the modules in the dependency graph of an application. During the compilation phase, modules are loaded, sealed, optimized, chunked, hashed and restored.

The Compilation class also extends Tapable and provides the following lifecycle hooks. They can be tapped the same way as compiler hooks:

compilation.hooks.someHook.tap(/* ... */);

As with the compiler, tapAsync and tapPromise may also be available depending on the type of hook.

buildModule

SyncHook

Triggered before a module build has started.

Parameters: module

rebuildModule

SyncHook

Fired before rebuilding a module.

Parameters: module

failedModule

SyncHook

Run when a module build has failed.

Parameters: module error

succeedModule

SyncHook

Executed when a module has been built successfully.

Parameters: module

finishModules

SyncHook

All modules have been built.

Parameters: modules

finishRebuildingModule

SyncHook

A module has been rebuilt.

Parameters: module

seal

SyncHook

Fired when the compilation stops accepting new modules.

unseal

SyncHook

Fired when a compilation begins accepting new modules.

optimizeDependenciesBasic

SyncBailHook

...

Parameters: modules

optimizeDependencies

SyncBailHook

Fired at the beginning of dependency optimization.

Parameters: modules

optimizeDependenciesAdvanced

SyncBailHook

...

Parameters: modules

afterOptimizeDependencies

SyncHook

...

Parameters: modules

optimize

SyncHook

Triggered at the beginning of the optimization phase.

optimizeModulesBasic

SyncBailHook

...

Parameters: modules

optimizeModules

SyncBailHook

...

Parameters: modules

optimizeModulesAdvanced

SyncBailHook

...

Parameters: modules

afterOptimizeModules

SyncHook

...

Parameters: modules

optimizeChunksBasic

SyncBailHook

...

Parameters: chunks

optimizeChunks

SyncBailHook

Optimize the chunks.

Parameters: chunks

optimizeChunksAdvanced

SyncBailHook

...

Parameters: chunks

afterOptimizeChunks

SyncHook

Fired after chunk optimization has completed.

Parameters: chunks

optimizeTree

AsyncSeriesHook

Optimize the dependency tree asynchronously.

Parameters: chunks modules

afterOptimizeTree

SyncHook

...

Parameters: chunks modules

optimizeChunkModulesBasic

SyncBailHook

...

Parameters: chunks modules

optimizeChunkModules

SyncBailHook

...

Parameters: chunks modules

optimizeChunkModulesAdvanced

SyncBailHook

...

Parameters: chunks modules

afterOptimizeChunkModules

SyncHook

...

Parameters: chunks modules

shouldRecord

SyncBailHook

...

reviveModules

SyncHook

Restore module information from records.

Parameters: modules records

optimizeModuleOrder

SyncHook

Sort the modules in from most to least important.

Parameters: modules

advancedOptimizeModuleOrder

SyncHook

...

Parameters: modules

beforeModuleIds

SyncHook

...

Parameters: modules

moduleIds

SyncHook

...

Parameters: modules

optimizeModuleIds

SyncHook

...

Parameters: chunks

afterOptimizeModuleIds

SyncHook

...

Parameters: chunks

reviveChunks

SyncHook

Restore chunk information from records.

Parameters: modules records

optimizeChunkOrder

SyncHook

Sort the chunks in from most to least important.

Parameters: chunks

beforeOptimizeChunkIds

SyncHook

Fired before chunk id optimization.

Parameters: chunks

optimizeChunkIds

SyncHook

Optimize the id of each chunk.

Parameters: chunks

afterOptimizeChunkIds

SyncHook

Triggered after chunk id optimization has finished.

Parameters: chunks

recordModules

SyncHook

Store module info to the records.

Parameters: modules records

recordChunks

SyncHook

Store chunk info to the records.

Parameters: chunks records

beforeHash

SyncHook

Before the compilation is hashed.

afterHash

SyncHook

After the compilation is hashed.

recordHash

SyncHook

...

Parameters: records

record

SyncHook

Store information about the compilation to the records.

Parameters: compilation records

beforeModuleAssets

SyncHook

...

shouldGenerateChunkAssets

SyncBailHook

...

beforeChunkAssets

SyncHook

Before creating the chunk assets.

additionalChunkAssets

SyncHook

Create additional assets for the chunks.

Parameters: chunks

records

SyncHook

...

Parameters: compilation records

additionalAssets

AsyncSeriesHook

Create additional assets for the compilation. This hook can be used to download an image, for example:

compilation.hooks.additionalAssets.tapAsync('MyPlugin', callback => {
  download('https://img.shields.io/npm/v/webpack.svg', function(resp) {
    if(resp.status === 200) {
      compilation.assets['webpack-version.svg'] = toAsset(resp);
      callback();
    } else {
      callback(new Error('[webpack-example-plugin] Unable to download the image'));
    }
  });
});

optimizeChunkAssets

AsyncSeriesHook

Optimize any chunk assets. The assets are stored in compilation.assets. A Chunk has a property files which points to all files created by a chunk. Any additional chunk assets are stored in compilation.additionalChunkAssets.

Parameters: chunks

Here's an example that simply adds a banner to each chunk.

compilation.hooks
  .optimizeChunkAssets
  .tapAsync('MyPlugin', (chunks, callback) => {
    chunks.forEach(chunk => {
      chunk.files.forEach(file => {
        compilation.assets[file] = new ConcatSource(
          '\/**Sweet Banner**\/',
          '\n',
          compilation.assets[file]
        );
      });
    });

    callback();
  });

afterOptimizeChunkAssets

SyncHook

The chunk assets have been optimized.

Parameters: chunks

Here's an example plugin from @boopathi that outputs exactly what went into each chunk.

compilation.hooks.afterOptimizeChunkAssets.tap('MyPlugin', chunks => {
  chunks.forEach(chunk => {
    console.log({
      id: chunk.id,
      name: chunk.name,
      includes: chunk.modules.map(module => module.request)
    });
  });
});

optimizeAssets

AsyncSeriesHook

Optimize all assets stored in compilation.assets.

Parameters: assets

afterOptimizeAssets

SyncHook

The assets has been optimized.

Parameters: assets

needAdditionalSeal

SyncBailHook

...

afterSeal

AsyncSeriesHook

...

chunkHash

SyncHook

...

Parameters: chunk chunkHash

moduleAsset

SyncHook

An asset from a module was added to the compilation.

Parameters: module filename

chunkAsset

SyncHook

An asset from a chunk was added to the compilation.

Parameters: chunk filename

assetPath

SyncWaterfallHook

...

Parameters: filename data

needAdditionalPass

SyncBailHook

...

childCompiler

SyncHook

...

Parameters: childCompiler compilerName compilerIndex

normalModuleLoader

SyncHook

The normal module loader is the function that actually loads all the modules in the module graph (one-by-one).

Parameters: loaderContext module

dependencyReference

SyncWaterfallHook

Compilation.hooks.dependencyReference(depRef, dependency, module) allows to change the references reported by dependencies.

Parameters: depRef dependency module