Webpack entry to Master four (Plugin principle)

preface

Earlier, we learned how the core webPack functionality enables source code transformation and packaging.

Based on the@babel/parserConvert the string toASTAbstract syntax tree.
rightASTFor modification, both to the source code modification.
usebabeltheAPIAnd then put the modifiedASTConvert to a new string (desired code).
And understandcss-loaderandstyle-loaderThe basic implementation of.

Let’s take a look at the usage scenarios and how the Plugin works.

Lead the problem

The basic code structure of a plug-in
The webPack build process
What does Tapable do by itself, and how does it link webPack plug-ins together?
compilerAs well ascompilationObject and the main API

The basic structure of the plug-in

Here is a simple version of the MD file into an HTML file a case

The use of plug-in

const {resolve} = require('path')
const MdToHtmlPlugin = require('./plugins/md-to-html-plugin')

module.exports = {
  mode: 'development'.entry: resolve(__dirname, 'src/app.js'),
  output: {
    path: resolve(__dirname, 'dist'),
    filename: 'app.js'
  },
  plugins: [
    new MdToHtmlPlugin({
      template: resolve(__dirname, 'test.md'),
      filename: 'test.html'}})]Copy the code

Define the plugin

const fs = require('fs')
const path = require('path')

function mdToHtml(mdStr) {
  let html = ' '
  // Filter out the empty ones
  let mdArrTemp = mdStr.split('\n').filter(item= >item ! = ="")
  //ol 1. 
  //ul - 
  //h2 ## 
  let olReg = /\d\.\s/,
      ulReg = /\-\s/,
      h2Reg = /\#{2}\s/

  mdArrTemp.forEach((item, index) = > {
    // There is no previous element, or the previous element is not the current traversal element
    let prev = mdArrTemp[index - 1];
    let next = mdArrTemp[index + 1];

    if (h2Reg.test(item)) {
      html += item.replace(h2Reg, "<h2>");
      html += "</h2>\n";
    } else if (ulReg.test(item)) {
      if(! prev || ! ulReg.test(prev)) { html +="<ul>\n";
      }
      html += item.replace(ulReg, " ");
      html += "</li>\n";
      if(! next || ! ulReg.test(next)) { html +="</ul>\n"; }}else if (olReg.test(item)) {
      if(! prev || ! olReg.test(prev)) { html +="<ol>\n";
      }
      html += item.replace(olReg, " ");
      html += "</li>\n";
      if(! next || ! olReg.test(next)) { html +="<ol>\n"; }}})return html
}

class MdToHtmlPlugin {
  // You can pass instance arguments inside the constructor
  constructor({template, filename}) {
    if(! template) {throw new Error('"template" must be configured')}this.template = template
    this.filename = filename
  }
  // Webpack calls the Apply method of the HelloPlugin instance to pass in the Compiler object to the plug-in.
  apply(compiler) {
    compiler.hooks.emit.tap("md-to-html-plugin".(compilation) = > {
      let _assets = compilation.assets
      // Read the original md file.
      let mdContent = fs.readFileSync(this.template, "utf-8");
      let htmlTemplateContent = fs.readFileSync(path.resolve(__dirname, './template.html')).toString()
      let html = mdToHtml(mdContent)
      // Read the template raw file.
      // Replace the format of the MD file with HTML.
      // Insert the HTML generated by the substitution into the HTML template file.
      let genHtml = htmlTemplateContent.replace("<! --md-->", html);
      fs.writeFileSync(path.resolve(__dirname, '.. /.. /dist/'+this.filename), genHtml, 'utf-8')}); }}module.exports = MdToHtmlPlugin;
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How does the plug-in work?

We use it first when reading the WebPack configurationnew MdToHtmlPlugin(options)I initialized oneMdToHtmlPluginThe instance
It’s also initialized in other codecompilerObject, calledMdToHtmlPlugin.apply(compiler)Method passed to the plug-incompilerObject.
The plug-in getscompilerObject can be calledcompiler.hooks.<hook name>.call. Specific events are documented.

node events && tabable

node

The Events module provides only one object: Events.EventEmitter. The core of EventEmitter is the encapsulation of event triggering and event listener functions.

var EventEmitter = require('events').EventEmitter; 
var event = new EventEmitter(); 
event.on('some_event'.function() { 
    console.log('some_event event triggered '); 
}); 
setTimeout(function() { 
    event.emit('some_event'); 
}, 1000); 
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tapable

github tapable

const { 
SyncHook,
SyncBailHook, 
SyncWaterfallHook,
SyncLoopHook,
AsyncParallelHook,
AsyncParallelBailHook,
AsyncSeriesHook, 
AsyncSeriesBailHook,
AsyncSeriesWaterfallHook
} = require("tapable");

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Implement a simple tapable

class Hook{
    constructor(args){
        this.taps = []
        this._args = args 
    }
    tap(name,fn){
        this.taps.push({name,fn})
    }
}
class SyncHook extends Hook{
    call(name,fn){
        try {
            this.taps.forEach(tap= > tap.fn(name))
            fn(null,name)
        } catch (error) {
            fn(error)
        }

    }
}

/ / use

let$=new SyncHook()
$.tap('xx'.() = > {console.log('xx')})
$.call('xx'.() = > {console.log('xx called')})
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Understand sync-type hooks

1, SyncHook

const {SyncHook} = require('tapable')

// Create an instance
const syncHook = new SyncHook(['name'.'age'])

// Register events

syncHook.tap('1'.(name, age) = > {
  console.log('1' ,name , age)
})

syncHook.tap("2".(name, age) = > {
  console.log("2", name, age);
});

syncHook.tap("3".(name, age) = > {
  console.log("3", name, age);
});

// Trigger the event to execute the callback function

syncHook.call('morning'.10)
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Understand Async hooks

1, AsyncSeriesHook

const { AsyncSeriesHook } = require("tapable");

// Create a real column
const asyncSeriesHook = new AsyncSeriesHook(["name"."age"]);

// Register events
asyncSeriesHook.tapAsync("1".(name, age, done) = > {
  setTimeout(() = > {
    console.log("1", name, age, new Date());
    done();
  }, 1000);
});

asyncSeriesHook.tapAsync("2".(name, age, done) = > {
  setTimeout(() = > {
    console.log("2", name, age, new Date());
    done();
  }, 2000);
});

asyncSeriesHook.tapAsync("3".(name, age, done) = > {
  setTimeout(() = > {
    console.log("3", name, age, new Date());
    done();
  }, 3000);
});

// Trigger the event to make the listener function execute
asyncSeriesHook.callAsync("Moon".10.() = > {
  console.log("Execution completed");
});
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How do Tapable and Webpack relate

Compiler.js

const { AsyncSeriesHook ,SyncHook } = require("tapable");
/ / create the class
class Compiler {
  constructor(options) {
    // Take the plugin from options and pass in the apply method
    this.hooks = {
      run: new SyncHook(["run"]), // Synchronize the hook
      compile: new AsyncSeriesHook(["name"."age"]), // Asynchronous hooks
      done: new SyncHook(['done'])}; options.plugins[0].apply(this);
  }
  run() {
    // Execute asynchronous hooks
    this.hooks.run.call();
    this.compile()
  }
  compile() {
    // Execute the sync hook and pass the parameter
    this.hooks.compile.callAsync("Moon".10.(err) = > {
      this.done();
    });
  }
  done() {
    this.hooks.done.call(); }}module.exports = Compiler
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MyPlugin.js

const Compiler = require("./Compiler");

class MyPlugin {
  apply(compiler) {
    // This is the hook,
    // Wait for the hook callback function to trigger within webpack at some point and add your own logic to it
    // Accept the compiler argument
    compiler.hooks.run.tap("MyPlugin".() = > console.log("Start compiling..."));
    // Trigger the asynchronous hook
    compiler.hooks.compile.tapAsync("MyPlugin".(name, age, done) = > {
      setTimeout(() = > {
        console.log('Compiling... Received parameter name:${name}-age:${age}Compilation of... `);
        done();
      }, 3000);
    });
    // Synchronize the hook
    compiler.hooks.done.tap("MyPlugin".() = > console.log("Finish compiling...")); }}This is similar to the plugins configuration for webpack.config.js
// Pass a new instance to the plugins property

const myPlugin = new MyPlugin();

const options = {
  plugins: [myPlugin],
};
let compiler = new Compiler(options);
compiler.run();

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After running the code above, you get the following output.

By the way, make fun of the code in the original text, and see several versions of the code.

Webpack build process

Verify configuration files: read command line incoming orwebpack.config.jsFile that initializes the configuration parameters for this build
generateCompilerObject: Executes the plug-in instantiation statement in the configuration filenew MyWebpackPlugin()forwebpackEvent flow hang customhooks
Enter theentryOptionPhase:webpackStart reading configurationEntries, recursively traverses all entry files
run/watch: If run inwatchMode executeswatchMethod, otherwise executerunmethods
compilation: createCompilationObject callbackcompilationRelated hooks to enter each entry file in turn (entry), use loader to compile the file. throughcompilationI can read itmoduletheresource(Resource path),loaders(Loader used). Then use the compiled file contentsacornParsing generates an AST static syntax tree. This process is then recursively and repeatedly executed after all modules and dependencies are analyzedcompilation 的 sealMethod To sort, optimize and encapsulate each chunk__webpack_require__To simulate modular operations.
emit: All files have been compiled and converted, containing the final output resources that we can call back to in the incoming eventcompilation.assetsGet the required data, including the resources to be exported, chunks of code, and so on.

// Modify or add the compilation. Assets ['new-file.js'] = {source() {return 'var a=1'; }, size() { return this.source().length; }}; Copy the codeCopy the code

afterEmit: The file has been written to the disk
doneFinish compiling

Again, with a picture

Compiler (is responsible for compiling)

The Compiler module is the main engine for WebPack and creates a Compilation instance through all the options passed through the CLI or Node API. It extends from the Tapable class to register and invoke plug-ins. Most user-oriented plug-ins are registered with Compiler first.

When developing plug-ins for WebPack, you may need to know where each hook function is called. To learn about this, search for hooks.

.call in the Webpack source code. Refer to plugins in webpack

Compilation (Responsible for creating bundles)

In a nutshell,Compilation is about building modules and chunks and optimizing the build process with plug-ins.

Commonly used API

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(); });Copy the code

Webpack document link

reference

Cnblogs nuggets

series

Getting started with Webpack to Mastering one (AST, Babel, Dependencies)

Getting started with Webpack to Mastering 2 (Core Principles)

Webpack entry to Master three (Loader principle)

Webpack entry to Master four (Plugin principle)

Webpack Getting started to Mastering 5 (Common Configuration)

Webpack entry to Master four (Plugin principle)

preface

Lead the problem

The basic structure of the plug-in

The use of plug-in

Define the plugin

How does the plug-in work?

node events && tabable

node

tapable

Implement a simple tapable

Understand sync-type hooks

1, SyncHook

Understand Async hooks

1, AsyncSeriesHook

How do Tapable and Webpack relate

Webpack build process

Compiler (is responsible for compiling)

Compilation (Responsible for creating bundles)

Commonly used API

series

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