feat: add support for resolve extensions esbuild setting

README.md

@@ -90,6 +90,7 @@ See [example folder](examples) for some example configurations.
 | `watch`                | Watch options for `serverless-offline`.                                                                                                                                                            | [Watch Options](#watch-options)                     |
 | `skipBuild`            | Avoid rebuilding lambda artifacts in favor of reusing previous build artifacts.                                                                                                                    | `false`                                             |
 | `skipBuildExcludeFns` | An array of lambda names that will always be rebuilt if `skipBuild` is set to `true` and bundling individually. This is helpful for dynamically generated functions like serverless-plugin-warmup. | `[]`                                                 |
+| `stripEntryResolveExtensions` | A boolean that determines if entrypoints using custom file extensions provided in the `resolveExtensions` ESbuild setting should be stripped of their custom extension upon packing the final bundle for that file. Example: `myLambda.custom.ts` would result in `myLambda.js` instead of `myLambda.custom.js`.
 
 #### Default Esbuild Options
 

src/bundle.ts

@@ -39,6 +39,7 @@ export async function bundle(this: EsbuildServerlessPlugin): Promise<void> {
     'nodeExternals',
     'skipBuild',
     'skipBuildExcludeFns',
+    'stripEntryResolveExtensions',
   ].reduce<Record<string, any>>((options, optionName) => {
     const { [optionName]: _, ...rest } = options;
 

src/constants.ts

@@ -2,3 +2,4 @@ export const SERVERLESS_FOLDER = '.serverless';
 export const BUILD_FOLDER = '.build';
 export const WORK_FOLDER = '.esbuild';
 export const ONLY_PREFIX = '__only_';
+export const DEFAULT_EXTENSIONS = ['.ts', '.js', '.jsx', '.tsx'];

src/helper.ts

@@ -9,8 +9,9 @@ import { uniq } from 'ramda';
 
 import type Serverless from 'serverless';
 import type ServerlessPlugin from 'serverless/classes/Plugin';
-import type { Configuration, DependencyMap, FunctionEntry } from './types';
+import type { Configuration, DependencyMap, FunctionEntry, IFile } from './types';
 import type { EsbuildFunctionDefinitionHandler } from './types';
+import { DEFAULT_EXTENSIONS } from './constants';
 
 export function asArray<T>(data: T | T[]): T[] {
   return Array.isArray(data) ? data : [data];
@@ -27,7 +28,8 @@ export function assertIsString(input: unknown, message = 'input is not a string'
 export function extractFunctionEntries(
   cwd: string,
   provider: string,
-  functions: Record<string, Serverless.FunctionDefinitionHandler>
+  functions: Record<string, Serverless.FunctionDefinitionHandler>,
+  resolveExtensions?: string[]
 ): FunctionEntry[] {
   // The Google provider will use the entrypoint not from the definition of the
   // handler function, but instead from the package.json:main field, or via a
@@ -69,7 +71,7 @@ export function extractFunctionEntries(
       // replace only last instance to allow the same name for file and handler
       const fileName = handler.substring(0, fnNameLastAppearanceIndex);
 
-      const extensions = ['.ts', '.js', '.jsx', '.tsx'];
+      const extensions = resolveExtensions ?? DEFAULT_EXTENSIONS;
 
       for (const extension of extensions) {
         // Check if the .{extension} files exists. If so return that to watch
@@ -313,3 +315,18 @@ export const buildServerlessV3LoggerFromLegacyLogger = (
   verbose: legacyLogger.log.bind(legacyLogger),
   success: legacyLogger.log.bind(legacyLogger),
 });
+
+export const stripEntryResolveExtensions = (file: IFile, extensions: string[]): IFile => {
+  const resolveExtensionMatch = file.localPath.match(extensions.map((ext) => ext).join('|'));
+
+  if (resolveExtensionMatch?.length && !DEFAULT_EXTENSIONS.includes(resolveExtensionMatch[0])) {
+    const extensionParts = resolveExtensionMatch[0].split('.');
+
+    return {
+      ...file,
+      localPath: file.localPath.replace(resolveExtensionMatch[0], `.${extensionParts[extensionParts.length - 1]}`),
+    };
+  }
+
+  return file;
+};

src/index.ts

@@ -320,6 +320,7 @@ class EsbuildServerlessPlugin implements ServerlessPlugin {
       outputFileExtension: '.js',
       skipBuild: false,
       skipBuildExcludeFns: [],
+      stripEntryResolveExtensions: false,
     };
 
     const providerRuntime = this.serverless.service.provider.runtime;
@@ -345,7 +346,12 @@ class EsbuildServerlessPlugin implements ServerlessPlugin {
   }
 
   get functionEntries() {
-    return extractFunctionEntries(this.serviceDirPath, this.serverless.service.provider.name, this.functions);
+    return extractFunctionEntries(
+      this.serviceDirPath,
+      this.serverless.service.provider.name,
+      this.functions,
+      this.buildOptions?.resolveExtensions
+    );
   }
 
   watch(): void {

src/pack.ts

@@ -9,7 +9,7 @@ import semver from 'semver';
 import type Serverless from 'serverless';
 
 import { ONLY_PREFIX, SERVERLESS_FOLDER } from './constants';
-import { assertIsString, doSharePath, flatDep, getDepsFromBundle, isESM } from './helper';
+import { assertIsString, doSharePath, flatDep, getDepsFromBundle, isESM, stripEntryResolveExtensions } from './helper';
 import { getPackager } from './packagers';
 import { humanSize, trimExtension, zip } from './utils';
 
@@ -114,7 +114,16 @@ export async function pack(this: EsbuildServerlessPlugin) {
       onlyFiles: true,
     })
     .filter((file) => !excludedFiles.includes(file))
-    .map((localPath) => ({ localPath, rootPath: path.join(buildDirPath, localPath) }));
+    .map((localPath) => ({ localPath, rootPath: path.join(buildDirPath, localPath) }))
+    .map((file) => {
+      if (this.buildOptions?.resolveExtensions && this.buildOptions.resolveExtensions.length > 0) {
+        if (this.buildOptions.stripEntryResolveExtensions) {
+          return stripEntryResolveExtensions(file, this.buildOptions.resolveExtensions);
+        }
+      }
+
+      return file;
+    });
 
   if (isEmpty(files)) {
     this.log.verbose('Packaging: No files found. Skipping esbuild.');

src/tests/helper.test.ts

@@ -2,9 +2,9 @@ import fs from 'fs-extra';
 import os from 'os';
 import path from 'path';
 
-import { extractFunctionEntries, flatDep, getDepsFromBundle, isESM } from '../helper';
+import { extractFunctionEntries, flatDep, getDepsFromBundle, isESM, stripEntryResolveExtensions } from '../helper';
 
-import type { Configuration, DependencyMap } from '../types';
+import type { Configuration, DependencyMap, IFile } from '../types';
 
 jest.mock('fs-extra');
 
@@ -135,6 +135,35 @@ describe('extractFunctionEntries', () => {
       ]);
     });
 
+    it('should allow resolve extensions custom Esbuild setting', () => {
+      jest.mocked(fs.existsSync).mockReturnValue(true);
+      const functionDefinitions = {
+        function1: {
+          events: [],
+          handler: './file1.handler',
+        },
+        function2: {
+          events: [],
+          handler: './file2.handler',
+        },
+      };
+
+      const fileNames = extractFunctionEntries(cwd, 'aws', functionDefinitions, ['.custom.ts']);
+
+      expect(fileNames).toStrictEqual([
+        {
+          entry: 'file1.custom.ts',
+          func: functionDefinitions.function1,
+          functionAlias: 'function1',
+        },
+        {
+          entry: 'file2.custom.ts',
+          func: functionDefinitions.function2,
+          functionAlias: 'function2',
+        },
+      ]);
+    });
+
     it('should not return entries for handlers which have skipEsbuild set to true', async () => {
       jest.mocked(fs.existsSync).mockReturnValue(true);
       const functionDefinitions = {
@@ -614,3 +643,15 @@ describe('flatDeps', () => {
     });
   });
 });
+
+describe('stripEntryResolveExtensions', () => {
+  it('should remove custom extension prefixes', () => {
+    const result = stripEntryResolveExtensions({ localPath: 'test.custom.js' } as IFile, ['.custom.js']);
+    expect(result.localPath).toEqual('test.js');
+  });
+
+  it('should ignore prefixes not inside the resolve extensions list', () => {
+    const result = stripEntryResolveExtensions({ localPath: 'test.other.js' } as IFile, ['.custom.js']);
+    expect(result.localPath).toEqual('test.other.js');
+  });
+});

src/types.ts

@@ -47,6 +47,7 @@ export interface Configuration extends EsbuildOptions {
   nodeExternals?: NodeExternalsOptions;
   skipBuild?: boolean;
   skipBuildExcludeFns: string[];
+  stripEntryResolveExtensions?: boolean;
 }
 
 export interface EsbuildFunctionDefinitionHandler extends Serverless.FunctionDefinitionHandler {