Resolve the path of a module like require.resolve() but from a given path

源码解析

"use strict";
const path = require("path");
const Module = require("module");
const fs = require("fs");

const resolveFrom = (fromDirectory, moduleId, silent) => {
  if (typeof fromDirectory !== "string") {
    throw new TypeError(
      `Expected \`fromDir\` to be of type \`string\`, got \`${typeof fromDirectory}\``
    );
  }

  if (typeof moduleId !== "string") {
    throw new TypeError(
      `Expected \`moduleId\` to be of type \`string\`, got \`${typeof moduleId}\``
    );
  }

  try {
    fromDirectory = fs.realpathSync(fromDirectory);
  } catch (error) {
    if (error.code === "ENOENT") {
      fromDirectory = path.resolve(fromDirectory);
    } else if (silent) {
      return;
    } else {
      throw error;
    }
  }

  // 这里不会影响代码执行 => 可以传入任意文件名称
  const fromFile = path.join(fromDirectory, "noop.js");

  const resolveFileName = () =>
    Module._resolveFilename(moduleId, {
      id: fromFile,
      filename: fromFile,
      paths: Module._nodeModulePaths(fromDirectory),
    });

  if (silent) {
    try {
      return resolveFileName();
    } catch (error) {
      return;
    }
  }

  return resolveFileName();
};

module.exports = (fromDirectory, moduleId) =>
  resolveFrom(fromDirectory, moduleId);
module.exports.silent = (fromDirectory, moduleId) =>
  resolveFrom(fromDirectory, moduleId, true);

.silent => 静默方法 === 如果有异常出现的话异常不会被抛出

1. 计算给定路径的规范路径名

fromDirectory = fs.realpathSync(fromDirectory);

通过fs.realpathSync() 方法 解析计算规范路径名

2. 获取所有可能的 node_modules 路径

paths: Module._nodeModulePaths(fromDirectory);

通过 Module._nodeModulePaths 内置方法获取当前目录下所有可能的 node_modules 路径

3. 获取绝对路径

const resolveFileName = () =>
  Module._resolveFilename(moduleId, {
    id: fromFile,
    filename: fromFile,
    paths: Module._nodeModulePaths(fromDirectory),
  });

return resolveFileName();

通过执行 Module._resolveFilename() 方法返回绝对路径

附：Module._nodeModulePaths 和 Module._resolveFilename 的执行流程