在JavaScript中如何使用宏详解

impl Component for MyComponent {
    // ...

    fn view(&self) -> Html {
        let onclick = self.link.callback(|_| Msg::Click);
        html! {
            { self.props.button_text }
        }
    }
}

import { gql } from 'graphql.macro';

const query = gql`
  query User {
    user(id: 5) {
      lastName
      ...UserEntry1
    }
  }
`;

//  在编译期会转换成 ↓ ↓ ↓ ↓ ↓ ↓

const query = {
  "kind": "Document",
  "definitions": [{
    ...

import preval from 'preval.macro'

const one = preval`module.exports = 1 + 2 - 1 - 1`

import preval from 'preval.macro'

const one = 1

'my.macro'
'my.macro.js'
'my.macro.cjs'
'my/macro'
'my/macro.js'
'my/macro.cjs'

import importURL from 'importurl.macros';

const React = importURL('https://unpkg.com/react@17.0.1/umd/react.development.js');

// 编译成

import importURL from 'importurl.macros';

const React = require('../cache/pkg1.js');

import { execSync } from 'child_process';
import findRoot from 'find-root';
import path from 'path';
import fse from 'fs-extra';

import { createMacro } from 'babel-plugin-macros';

const syncGet = (url) => {
  const data = execSync(`curl -L ${url}`).toString();
  if (data === '') {
    throw new Error('empty data');
  }
  return data;
}

let count = 0;
export const genUniqueName = () => `pkg${++count}.js`;

module.exports = createMacro((ctx) => {
  const {
    references, // 文件中所有对宏的引用
    babel: {
      types: t,
    }
  } = ctx;
  // babel 会把当前处理的文件路径设置到 ctx.state.filename
  const workspacePath = findRoot(ctx.state.filename);
  // 计算出缓存文件夹
  const cacheDirPath = path.join(workspacePath, '.cache');
  //
  const calls = references.default.map(path => path.findParent(path => path.node.type === 'CallExpression' ));
  calls.forEach(nodePath => {
    // 确定 astNode 的类型
    if (nodePath.node.type === 'CallExpression') {
      // 确定函数的第一个参数是纯字符串
      if (nodePath.node.arguments[0]?.type === 'StringLiteral') {
        // 获取一个参数，当做远程库的地址
        const url = nodePath.node.arguments[0].value;
        // 根据 url 拉取代码
        const codes = syncGet(url);
        // 生成一个唯一包名，防止冲突
        const pkgName = genUniqueName();
        // 确定最终要写入的文件路径
        const cahceFilename = path.join(cacheDirPath, pkgName);
        // 通过 fse 库，将内容写入， outputFileSync 会自动创建不存在的文件夹
        fse.outputFileSync(cahceFilename, codes);
        // 计算出相对路径
        const relativeFilename = path.relative(ctx.state.filename, cahceFilename);
        // 最终计算替换 importURL 语句
        nodePath.replaceWith(t.stringLiteral(`require('${relativeFilename}')`))
      }
    }
  });
});

function createMacro(handler: MacroHandler, options?: Options): any;
interface MacroParams {
      references: { default: Babel.NodePath[] } & References;
      state: Babel.PluginPass;
      babel: typeof Babel;
      config?: { [key: string]: any };
  }
export interface PluginPass {
    file: BabelFile;
    key: string;
    opts: PluginOptions;
    cwd: string;
    filename: string;
    [key: string]: unknown;
}

import importURL from 'importurl.macros';

const React = importURL('https://unpkg.com/react@17.0.1/umd/react.development.js');

const syncGet = (url) => {
  const data = execSync(`curl -L ${url}`).toString();
  if (data === '') {
    throw new Error('empty data');
  }
  return data;
}