Improve code readability

Author: Septh

src/index.ts

@@ -3,16 +3,16 @@ import { builtinModules } from 'module'
 import { findPackagePaths, findDependencies } from './dependencies'
 
 export interface ExternalsOptions {
+    /** Mark node built-in modules like `path`, `fs`... as external. Defaults to `true`. */
+    builtins?: boolean
+    /** How to treat prefixed builtins. Defaults to `true` (prefixed are considered the same as unprefixed). */
+    prefixedBuiltins?: boolean | 'strip'
     /**
      * Path/to/your/package.json file (or array of paths).
      * Defaults to all package.json files found in parent directories recursively.
      * Won't got outside of a git repository.
      */
     packagePath?: string | string[]
-    /** Mark node built-in modules like `path`, `fs`... as external. Defaults to `true`. */
-    builtins?: boolean
-    /** Treat prefixed builtins as their unprefixed counterpart. Optional. Default: true */
-    prefixedBuiltins?: boolean | 'strip'
     /** Mark dependencies as external. Defaults to `true`. */
     deps?: boolean
     /** Mark devDependencies as external. Defaults to `true`. */
@@ -27,7 +27,7 @@ export interface ExternalsOptions {
     exclude?: string | RegExp | (string | RegExp)[]
 }
 
-type IncludeExclude = Extract<keyof ExternalsOptions, 'include' | 'exclude'>
+type IncludeExclude = Pick<ExternalsOptions, 'include' | 'exclude'>
 
 /**
  * A Rollup plugin that automatically declares NodeJS built-in modules,
@@ -37,9 +37,9 @@ function externals(options: ExternalsOptions = {}): Plugin {
 
     // Consolidate options
     const config: Required<ExternalsOptions> = {
-        packagePath: [],
         builtins: true,
         prefixedBuiltins: 'strip',
+        packagePath: [],
         deps: true,
         devDeps: true,
         peerDeps: true,
@@ -49,32 +49,31 @@ function externals(options: ExternalsOptions = {}): Plugin {
         ...options
     }
 
-    // This will store all eventual warnings until we can display them
+    // This will store all eventual warnings until we can display them.
     const warnings: string[] = []
 
-    // Map the include and exclude options to arrays of regexes
-    const [ include, exclude ] = ([ 'include', 'exclude' ] as IncludeExclude[]).map(optionName => ([] as (string | RegExp)[])
-        .concat(config[optionName])
+    // Map the include and exclude options to arrays of regexes.
+    const [ include, exclude ] = [ 'include', 'exclude' ].map(option => new Array<string | RegExp>()
+        .concat(config[option as keyof IncludeExclude])
         .map((entry, index) => {
-            if (entry instanceof RegExp) {
+            if (entry instanceof RegExp)
                 return entry
-            }
-            else if (typeof entry === 'string') {
+
+            if (typeof entry === 'string')
                 return new RegExp('^' + entry.replace(/[.*+?^${}()|[\]\\]/g, '\\$&') + '$')
+
+            if (entry) {
+                warnings.push(`Ignoring wrong entry type #${index} in '${option}' option: '${entry}'`)
             }
-            else {
-                if (entry) {
-                    warnings.push(`Ignoring wrong entry type #${index} in '${optionName}' option: '${entry}'`)
-                }
-                return /(?=no)match/
-            }
+
+            return /(?=no)match/
         })
     )
 
-    // Filter function to keep only non excluded dependencies
+    // A filter function to keep only non excluded dependencies.
     const isNotExcluded = (id: string) => !exclude.some(rx => rx.test(id))
 
-    // Array of the final regexes
+    // The array of the final regexes.
     const externals: RegExp[] = []
     const isExternal = (id: string) => externals.some(rx => rx.test(id))
 
@@ -83,21 +82,21 @@ function externals(options: ExternalsOptions = {}): Plugin {
 
         async buildStart() {
 
-            // 1) Filter NodeJS builtins, supporting potential import from a sub directory (e.g. 'fs/promises')
+            // 1) Filter NodeJS builtins, supporting potential import from a sub directory (e.g. 'fs/promises').
             const builtins = (config.builtins ? builtinModules : []).filter(isNotExcluded)
             if (builtins.length > 0) {
                 externals.push(new RegExp(`^(?:${builtins.join('|')})(?:/.+)?$`))
             }
 
-            // 2) Find and filter dependencies, supporting potential import from a sub directory (e.g. 'lodash/map')
+            // 2) Find and filter dependencies, supporting potential import from a sub directory (e.g. 'lodash/map').
             const packagePaths: string[] = ([] as string[]).concat(config.packagePath)
             const dependencies = (await findDependencies({
                 packagePaths: packagePaths.length > 0 ? packagePaths : findPackagePaths(),
                 keys: [
-                    config.deps && 'dependencies',
-                    config.devDeps && 'devDependencies',
+                    config.deps     && 'dependencies',
+                    config.devDeps  && 'devDependencies',
                     config.peerDeps && 'peerDependencies',
-                    config.optDeps && 'optionalDependencies'
+                    config.optDeps  && 'optionalDependencies'
                 ].filter(Boolean) as string[],
                 warnings
             })).filter(isNotExcluded)
@@ -106,12 +105,12 @@ function externals(options: ExternalsOptions = {}): Plugin {
                 externals.push(new RegExp(`^(?:${dependencies.join('|')})(?:/.+)?$`))
             }
 
-            // 3) Add the include option
+            // 3) Add the include option.
             if (include.length > 0) {
                 externals.push(...include)
             }
 
-            // All done. Issue the warnings we may have collected
+            // All done. Issue the warnings we may have collected.
             while (warnings.length > 0) {
                 // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
                 this.warn(warnings.shift()!)
@@ -120,12 +119,12 @@ function externals(options: ExternalsOptions = {}): Plugin {
 
         resolveId(importee, importer, { isEntry }) {
 
-            // Ignore entry chunks & don't mess with other plugins
+            // Ignore entry chunks & don't mess with other plugins.
             if (isEntry || !importee.charCodeAt(0) || !importer?.charCodeAt(0)) {
                 return null
             }
 
-            // Remove node:/nodejs: prefix so builtins resolve to their unprefixed equivalent
+            // Remove node:/nodejs: prefix so builtins resolve to their unprefixed equivalent.
             let stripped = importee
             if (config.prefixedBuiltins) {
                 if (importee.startsWith('node:')) {
@@ -137,7 +136,7 @@ function externals(options: ExternalsOptions = {}): Plugin {
             }
 
             // Return object if importee should be treated as an external module,
-            // otherwise return `null` to let Rollup and other plugins handle it
+            // otherwise return `null` to let Rollup and other plugins handle it.
             return isExternal(stripped) && isNotExcluded(stripped)
                 ? { id: config.prefixedBuiltins === 'strip' ? stripped : importee, external: true }
                 : null