fix: cache usage of modern-node-polyfills API (#115)

Co-authored-by: parbez <imranbarbhuiya.fsd@gmail.com>

src/lib/plugin.ts

@@ -1,9 +1,7 @@
 import { builtinModules } from 'node:module';
 import path from 'node:path';
 
-import { polyfillContent, polyfillPath } from 'modern-node-polyfills';
-
-import { escapeRegex, commonJsTemplate, removeEndingSlash } from './utils/util.js';
+import { escapeRegex, commonJsTemplate, getCachedPolyfillPath, getCachedPolyfillContent } from './utils/util.js';
 
 import type { OnResolveArgs, Plugin } from 'esbuild';
 import type esbuild from 'esbuild';
@@ -19,9 +17,7 @@ const loader = async (args: esbuild.OnLoadArgs): Promise<esbuild.OnLoadResult> =
 	try {
 		const isCommonjs = args.namespace.endsWith('commonjs');
 
-		const resolved = await polyfillPath(removeEndingSlash(args.path));
-		const contents = (await polyfillContent(removeEndingSlash(args.path))).replaceAll('eval(', '(0,eval)(');
-
+		const resolved = await getCachedPolyfillPath(args.path);
 		const resolveDir = path.dirname(resolved);
 
 		if (isCommonjs) {
@@ -34,6 +30,8 @@ const loader = async (args: esbuild.OnLoadArgs): Promise<esbuild.OnLoadResult> =
 			};
 		}
 
+		const contents = await getCachedPolyfillContent(args.path);
+
 		return {
 			loader: 'js',
 			contents,
@@ -72,7 +70,7 @@ export const nodeModulesPolyfillPlugin = (options: NodePolyfillsOptions = {}): P
 			const resolver = async (args: OnResolveArgs) => {
 				const ignoreRequire = args.namespace === commonjsNamespace;
 
-				const pollyfill = await polyfillPath(args.path).catch(() => null);
+				const pollyfill = await getCachedPolyfillPath(args.path).catch(() => null);
 
 				if (!pollyfill) {
 					return;

src/lib/utils/util.ts

@@ -1,12 +1,10 @@
 /* eslint-disable unicorn/prefer-string-replace-all -- node v14 doesn't supports string.replaceAll*/
+import { polyfillContent, polyfillPath } from 'modern-node-polyfills';
+
 export const escapeRegex = (str: string) => {
 	return str.replace(/[$()*+.?[\\\]^{|}]/g, '\\$&').replace(/-/g, '\\x2d');
 };
 
-export const removeEndingSlash = (str: string) => {
-	return str.replace(/\/$/, '');
-};
-
 export const commonJsTemplate = ({ importPath }: { importPath: string }) => {
 	return `
 const polyfill = require('${importPath}')
@@ -20,3 +18,40 @@ if (polyfill && polyfill.default) {
 }
 `;
 };
+
+const normalizeNodeBuiltinPath = (path: string) => {
+	return path.replace(/^node:/, '').replace(/\/$/, '');
+};
+
+const polyfillPathCache: Map<string, Promise<string>> = new Map();
+export const getCachedPolyfillPath = (_importPath: string): Promise<string> => {
+	const normalizedImportPath = normalizeNodeBuiltinPath(_importPath);
+
+	const cachedPromise = polyfillPathCache.get(normalizedImportPath);
+	if (cachedPromise) {
+		return cachedPromise;
+	}
+
+	const promise = polyfillPath(normalizedImportPath);
+	polyfillPathCache.set(normalizedImportPath, promise);
+	return promise;
+};
+
+const polyfillContentAndTransform = async (importPath: string) => {
+	const content = await polyfillContent(importPath);
+	return content.replace(/eval\(/g, '(0,eval)(');
+};
+
+const polyfillContentCache: Map<string, Promise<string>> = new Map();
+export const getCachedPolyfillContent = (_importPath: string): Promise<string> => {
+	const normalizedImportPath = normalizeNodeBuiltinPath(_importPath);
+
+	const cachedPromise = polyfillContentCache.get(normalizedImportPath);
+	if (cachedPromise) {
+		return cachedPromise;
+	}
+
+	const promise = polyfillContentAndTransform(normalizedImportPath);
+	polyfillContentCache.set(normalizedImportPath, promise);
+	return promise;
+};