Javascript 网页包源代码映射奇怪的行为

我遇到了Webpack（4.35.2）的一个奇怪行为，在

devtool:“sourcemap”

时调用了我的函数两次

这里有一个简单的复制结构：

index.js

(function test() {
    console.log("function test");
})();

import t from "./index";

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");

module.exports = {
    entry: {
        index: "./index.js",
        other: "./other.js"
    },
    output: {
        path: path.resolve(__dirname, "dist"),
        filename: "[name].js"
    },
    module: {
        rules: [
            {
                test: /\.js?$/,
                exclude: /(node_modules)/,
                loader: "babel-loader",
                options: {
                    presets: ["@babel/preset-env"]
                }
            }
        ]
    },
    plugins: [
        new HtmlWebpackPlugin({
            filename: "index.html"
        })
    ],

    devtool: "source-map",

    devServer: {
        contentBase: path.join(__dirname, "dist"),
        compress: true
    }
};

other.js

(function test() {
    console.log("function test");
})();

import t from "./index";

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");

module.exports = {
    entry: {
        index: "./index.js",
        other: "./other.js"
    },
    output: {
        path: path.resolve(__dirname, "dist"),
        filename: "[name].js"
    },
    module: {
        rules: [
            {
                test: /\.js?$/,
                exclude: /(node_modules)/,
                loader: "babel-loader",
                options: {
                    presets: ["@babel/preset-env"]
                }
            }
        ]
    },
    plugins: [
        new HtmlWebpackPlugin({
            filename: "index.html"
        })
    ],

    devtool: "source-map",

    devServer: {
        contentBase: path.join(__dirname, "dist"),
        compress: true
    }
};

webpack.config.js

(function test() {
    console.log("function test");
})();

import t from "./index";

const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");

module.exports = {
    entry: {
        index: "./index.js",
        other: "./other.js"
    },
    output: {
        path: path.resolve(__dirname, "dist"),
        filename: "[name].js"
    },
    module: {
        rules: [
            {
                test: /\.js?$/,
                exclude: /(node_modules)/,
                loader: "babel-loader",
                options: {
                    presets: ["@babel/preset-env"]
                }
            }
        ]
    },
    plugins: [
        new HtmlWebpackPlugin({
            filename: "index.html"
        })
    ],

    devtool: "source-map",

    devServer: {
        contentBase: path.join(__dirname, "dist"),
        compress: true
    }
};

如果运行它，

test（）

将被调用两次。
然后将

devtool

更改为其他内容，它会被调用一次（我认为它应该被调用）

有人知道发生了什么吗