From b483e401b3f5b9aacd3797da3f96b1c664a4e02c Mon Sep 17 00:00:00 2001
From: Luke Edwards <luke.edwards05@gmail.com>
Date: Tue, 26 Oct 2021 19:22:53 -0700
Subject: [PATCH] fix: support new API for ESM loader hooks (#16)

* chore(loader): rename `load` ~> `toConfig` helper

* chore(loader): add deprecated note to self

* fix(loader): add new `load` hook for new API design;

- Closes #13
---
 .github/workflows/ci.yml |  2 +-
 src/loader.ts            | 45 +++++++++++++++++++++++++++++++++++-----
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 08059c4..fec0e23 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -15,7 +15,7 @@ jobs:
     timeout-minutes: 3
     strategy:
       matrix:
-        nodejs: [12, 14, 16]
+        nodejs: [12, 14, 16.11, 16]
         os: [ubuntu-latest, windows-latest]
     steps:
     - uses: actions/checkout@v2
diff --git a/src/loader.ts b/src/loader.ts
index 546c4db..6f0b195 100644
--- a/src/loader.ts
+++ b/src/loader.ts
@@ -1,4 +1,4 @@
-import { existsSync } from 'fs';
+import { existsSync, promises as fs } from 'fs';
 import { fileURLToPath, URL } from 'url';
 import * as tsm from './utils.js';
 
@@ -22,7 +22,10 @@ type Resolve = (
 		parentURL?: string;
 	},
 	fallback: Resolve
-) => Promisable<{ url: string }>;
+) => Promisable<{
+	url: string;
+	format?: Format;
+}>;
 
 type Inspect = (
 	url: string,
@@ -36,7 +39,16 @@ type Transform = (
 	fallback: Transform
 ) => Promisable<{ source: Source }>;
 
-async function load(): Promise<Config> {
+type Load = (
+	url: string,
+	context: { format?: Format },
+	fallback: Load
+) => Promisable<{
+	format: Format;
+	source: Source;
+}>;
+
+async function toConfig(): Promise<Config> {
 	let mod = await setup;
 	mod = mod && mod.default || mod;
 	return (tsm as TSM).$finalize(env, mod);
@@ -46,7 +58,7 @@ const EXTN = /\.\w+(?=\?|$)/;
 const isTS = /\.[mc]?tsx?(?=\?|$)/;
 const isJS = /\.([mc])?js$/;
 async function toOptions(uri: string): Promise<Options|void> {
-	config = config || await load();
+	config = config || await toConfig();
 	let [extn] = EXTN.exec(uri) || [];
 	return config[extn as `.${string}`];
 }
@@ -91,7 +103,7 @@ export const resolve: Resolve = async function (ident, context, fallback) {
 		}
 	}
 
-	config = config || await load();
+	config = config || await toConfig();
 
 	for (ext in config) {
 		path = check(output.href + ext);
@@ -101,12 +113,35 @@ export const resolve: Resolve = async function (ident, context, fallback) {
 	return fallback(ident, context, fallback);
 }
 
+export const load: Load = async function (uri, context, fallback) {
+	// note: inline `getFormat`
+	let options = await toOptions(uri);
+	if (options == null) return fallback(uri, context, fallback);
+	let format: Format = options.format === 'cjs' ? 'commonjs' : 'module';
+
+	// TODO: decode SAB/U8 correctly
+	let path = fileURLToPath(uri);
+	let source = await fs.readFile(path);
+
+	// note: inline `transformSource`
+	esbuild = esbuild || await import('esbuild');
+	let result = await esbuild.transform(source.toString(), {
+		...options,
+		sourcefile: path,
+		format: format === 'module' ? 'esm' : 'cjs',
+	});
+
+	return { format, source: result.code };
+}
+
+/** @deprecated */
 export const getFormat: Inspect = async function (uri, context, fallback) {
 	let options = await toOptions(uri);
 	if (options == null) return fallback(uri, context, fallback);
 	return { format: options.format === 'cjs' ? 'commonjs' : 'module' };
 }
 
+/** @deprecated */
 export const transformSource: Transform = async function (source, context, xform) {
 	let options = await toOptions(context.url);
 	if (options == null) return xform(source, context, xform);