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, can be used to modify the module.

  • Callback Parameters: module
compilation.hooks.buildModule.tap('SourceMapDevToolModuleOptionsPlugin',
  module => {
    module.useSourceMap = true;
  }
);

rebuildModule

SyncHook

Fired before rebuilding a module.

  • Callback Parameters: module

failedModule

SyncHook

Run when a module build has failed.

  • Callback Parameters: module error

succeedModule

SyncHook

Executed when a module has been built successfully.

  • Callback Parameters: module

finishModules

AsyncSeriesHook

Called when all modules have been built without errors.

  • Callback Parameters: modules

finishRebuildingModule

SyncHook

Executed when a module has been rebuilt, in case of both success or with errors.

  • Callback Parameters: module

seal

SyncHook

Fired when the compilation stops accepting new modules.

unseal

SyncHook

Fired when a compilation begins accepting new modules.

optimizeDependenciesBasic

SyncBailHook

This hook will be removed in v5.0.0

Parameters: modules

optimizeDependencies

SyncBailHook

Fired at the beginning of dependency optimization.

  • Callback Parameters: modules

optimizeDependenciesAdvanced

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: modules

afterOptimizeDependencies

SyncHook

Fired after the dependency optimization.

  • Callback Parameters: modules

optimize

SyncHook

Triggered at the beginning of the optimization phase.

optimizeModulesBasic

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: modules

optimizeModules

SyncBailHook

Called at the beginning of the modules optimization phase. A plugin can tap into this hook to perform modules optimizations.

  • Callback Parameters: modules

optimizeModulesAdvanced

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: modules

afterOptimizeModules

SyncHook

Called after modules optimization has completed.

  • Callback Parameters: modules

optimizeChunksBasic

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: chunks

optimizeChunks

SyncBailHook

Called at the beginning of the chunks optimizion phase. A plugin can tap into this hook to perform chunks optimizations.

  • Callback Parameters: chunks

optimizeChunksAdvanced

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: chunks

afterOptimizeChunks

SyncHook

Fired after chunk optimization has completed.

  • Callback Parameters: chunks

optimizeTree

AsyncSeriesHook

Called before optimizing the dependency tree. A plugin can tap into this hook to perform a dependency tree optimization.

  • Callback Parameters: chunks modules

afterOptimizeTree

SyncHook

Called after the dependency tree optimization has completed with success.

  • Callback Parameters: chunks modules

optimizeChunkModulesBasic

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: chunks modules

optimizeChunkModules

SyncBailHook

Called after the tree optimization, at the beginning of the chunk modules optimization. A plugin can tap into this hook to perform optimizations of chunk modules.

  • Callback Parameters: chunks modules

optimizeChunkModulesAdvanced

SyncBailHook

This hook will be removed in v5.0.0

  • Callback Parameters: chunks modules

afterOptimizeChunkModules

SyncHook

Called after the chunkmodules optimization has successfully completed.

  • Callback Parameters: chunks modules

shouldRecord

SyncBailHook

Called to determine whether or not to store records. Returning anything !== false will prevent every other "record" hook from being executed (record, recordModules, recordChunks and recordHash).

reviveModules

SyncHook

Restore module information from records.

  • Callback Parameters: modules records

optimizeModuleOrder

SyncHook

This hook will be removed in v5.0.0

Sort the modules from most to least important.

  • Callback Parameters: modules

advancedOptimizeModuleOrder

SyncHook

This hook will be removed in v5.0.0

  • Callback Parameters: modules

beforeModuleIds

SyncHook

Executed before assigning an id to each module.

  • Callback Parameters: modules

moduleIds

SyncHook

Called to assign an id to each module.

  • Callback Parameters: modules

optimizeModuleIds

SyncHook

Called at the beginning of the modules id optimization.

  • Callback Parameters: modules

afterOptimizeModuleIds

SyncHook

Called when the modules id optimization phase has completed.

  • Callback Parameters: modules

reviveChunks

SyncHook

Restore chunk information from records.

  • Callback Parameters: chunks records

optimizeChunkOrder

SyncHook

This hook will be removed in v5.0.0

Sort the chunks in from most to least important.

  • Callback Parameters: chunks

beforeChunkIds

SyncHook

Executed before assigning an id to each chunk.

  • Callback Parameters: chunks

chunkIds

SyncHook

This hook will be available in v5.0.0

Called to assign an id to each chunk.

  • Callback Parameters: modules

beforeOptimizeChunkIds

SyncHook

This hook will be available in v5.0.0

Fired before chunks id optimization.

  • Callback Parameters: chunks

optimizeChunkIds

SyncHook

Called at the beginning of the chunks id optimization phase.

  • Callback Parameters: chunks

afterOptimizeChunkIds

SyncHook

Triggered after chunk id optimization has finished.

  • Callback Parameters: chunks

recordModules

SyncHook

Store module info to the records. This is triggered if shouldRecord returns a truthy value.

  • Callback Parameters: modules records

recordChunks

SyncHook

Store chunk info to the records. This is only triggered if shouldRecord returns a truthy value.

  • Callback Parameters: chunks records

optimizeCodeGeneration

This hook will be available in v5.0.0

A plugin can tap into this hook to optimize the generated code.

  • Callback Parameters: modules

beforeModuleHash

This hook will be available in v5.0.0

Called before hashing modules.

afterModuleHash

This hook will be available in v5.0.0

Called after hashing modules.

beforeRuntimeRequirements

This hook will be available in v5.0.0

Called before processing the modules required at runtime.

  • Callback Parameters: entrypoints

afterRuntimeRequirements

This hook will be available in v5.0.0

Called after processing the runtime requirements.

beforeHash

SyncHook

Called before the compilation is hashed.

afterHash

SyncHook

Called after the compilation is hashed.

recordHash

SyncHook

Store information about record hash to the records. This is only triggered if shouldRecord returns a truthy value.

  • Callback Parameters: records

record

SyncHook

Store information about the compilation to the records. This is only triggered if shouldRecord returns a truthy value.

  • Callback Parameters: compilation records

beforeModuleAssets

SyncHook

Executed before module assets creation.

additionalChunkAssets

SyncHook

Create additional assets for the chunks.

  • Callback Parameters: chunks

shouldGenerateChunkAssets

SyncBailHook

Called to determine wheter or not generate chunks assets. Returning anything !== false will allow chunk assets generation.

beforeChunkAssets

SyncHook

Executed before creating the chunks assets.

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.

  • Callback 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.

  • Callback 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.getModules().map(module => module.request)
    });
  });
});

optimizeAssets

AsyncSeriesHook

Optimize all assets stored in compilation.assets.

  • Callback Parameters: assets

afterOptimizeAssets

SyncHook

The assets have been optimized.

  • Callback Parameters: assets

needAdditionalSeal

SyncBailHook

Called to determine if the compilation needs to be unsealed to include other files.

afterSeal

AsyncSeriesHook

Executed right after needAdditionalSeal.

chunkHash

SyncHook

Triggered to emit the hash for each chunk.

  • Callback Parameters: chunk chunkHash

moduleAsset

SyncHook

Called when an asset from a module was added to the compilation.

  • Callback Parameters: module filename

chunkAsset

SyncHook

Triggered when an asset from a chunk was added to the compilation.

  • Callback Parameters: chunk filename

assetPath

SyncWaterfallHook

Called to determine the path of an asset.

  • Callback Parameters: path options

needAdditionalPass

SyncBailHook

Called to determine if a asset need to be processed further after being emitted.

childCompiler

SyncHook

Executed after setting up a child compiler.

  • Callback Parameters: childCompiler compilerName compilerIndex

normalModuleLoader

Since webpack v5 normalModuleLoader hook was removed. Now to access the loader use NormalModule.getCompilationHooks(compilation).loader instead.

dependencyReference

SyncWaterfallHook

This hooks allows changing the references reported by dependencies.

  • Callback Parameters: depRef dependency module

The module parameter will be removed in v5.0.0