fix: obeys esbuild's external argument

mod_test.ts

@@ -6,7 +6,7 @@ import {
 } from "./mod.ts";
 import { denoLoaderPlugin } from "./src/plugin_deno_loader.ts";
 import { esbuildNative, esbuildWasm, join } from "./test_deps.ts";
-import { assert, assertEquals } from "./test_deps.ts";
+import { assert, assertEquals, assertStringIncludes } from "./test_deps.ts";
 
 await esbuildNative.initialize({});
 await esbuildWasm.initialize({});
@@ -657,3 +657,25 @@ Deno.test("uncached data url", async (t) => {
     assertEquals(value, rand);
   });
 });
+
+Deno.test("externals", async (t) => {
+  await testLoader(t, LOADERS, async (esbuild, loader) => {
+    const configPath = join(Deno.cwd(), "testdata", "config_ref.json");
+    const res = await esbuild.build({
+      ...DEFAULT_OPTS,
+      plugins: [
+        ...denoPlugins({ configPath, loader }),
+      ],
+      bundle: true,
+      platform: "neutral",
+      entryPoints: ["./testdata/externals.ts"],
+      external: ["foo:bar", "foo:baz/*", "bar"],
+    });
+    assertEquals(res.warnings, []);
+    assertEquals(res.errors, []);
+    assertEquals(res.outputFiles.length, 1);
+    const output = res.outputFiles[0];
+    assertStringIncludes(output.text, "foo:bar");
+    assertStringIncludes(output.text, "foo:baz/bar");
+  });
+});

src/plugin_deno_resolver.ts

@@ -47,6 +47,17 @@ export function denoResolverPlugin(
       let importMap: ImportMap | null = null;
       let nodeModulesPaths: Set<string>;
 
+      const externalRegexps: RegExp[] = (build.initialOptions.external ?? [])
+        .map((external) => {
+          const regexp = new RegExp(
+            "^" + external.replace(/[-/\\^$+?.()|[\]{}]/g, "\\$&").replace(
+              /\*/g,
+              ".*",
+            ) + "$",
+          );
+          return regexp;
+        });
+
       build.onStart(async function onStart() {
         nodeModulesPaths = new Set<string>();
 
@@ -139,6 +150,15 @@ export function denoResolverPlugin(
           resolved = new URL(args.path, referrer);
         }
 
+        for (const externalRegexp of externalRegexps) {
+          if (externalRegexp.test(resolved.href)) {
+            return {
+              path: resolved.href,
+              external: true,
+            };
+          }
+        }
+
         // Now pass the resolved specifier back into the resolver, for a second
         // pass. Now plugins can perform any resolution they want on the fully
         // resolved specifier.

test_deps.ts

@@ -4,6 +4,7 @@ export { esbuildNative, esbuildWasm };
 export {
   assert,
   assertEquals,
+  assertStringIncludes,
   assertThrows,
 } from "https://deno.land/[email protected]/assert/mod.ts";
 export { join } from "https://deno.land/[email protected]/path/mod.ts";

testdata/externals.ts

@@ -0,0 +1,2 @@
+export { a } from "foo:bar";
+export { b } from "foo:baz/bar";