fix(typescript): change the value of isExternalLibraryImport to false if the resolvedModule should be compiled

packages/typescript/src/index.ts

@@ -42,7 +42,7 @@ export default function typescript(options: RollupTypescriptOptions = {}): Plugi
   parsedOptions.fileNames = parsedOptions.fileNames.filter(filter);
 
   const formatHost = createFormattingHost(ts, parsedOptions.options);
-  const resolveModule = createModuleResolver(ts, formatHost);
+  const resolveModule = createModuleResolver(ts, formatHost, filter);
 
   let program: Watch<unknown> | null = null;
 

packages/typescript/src/moduleResolution.ts

@@ -5,6 +5,7 @@ import type {
   ResolvedProjectReference,
   ModuleKind
 } from 'typescript';
+import type { CreateFilter } from '@rollup/pluginutils';
 
 import type { DiagnosticsHost } from './diagnostics/host';
 
@@ -24,7 +25,8 @@ export type Resolver = (
  */
 export default function createModuleResolver(
   ts: typeof typescript,
-  host: ModuleResolverHost
+  host: ModuleResolverHost,
+  filter: ReturnType<CreateFilter>
 ): Resolver {
   const compilerOptions = host.getCompilationSettings();
   const cache = ts.createModuleResolutionCache(
@@ -35,7 +37,7 @@ export default function createModuleResolver(
   const moduleHost = { ...ts.sys, ...host };
 
   return (moduleName, containingFile, redirectedReference, mode) => {
-    const resolved = ts.resolveModuleName(
+    const { resolvedModule } = ts.resolveModuleName(
       moduleName,
       containingFile,
       compilerOptions,
@@ -44,6 +46,13 @@ export default function createModuleResolver(
       redirectedReference,
       mode
     );
-    return resolved.resolvedModule;
+    /**
+     * If the module's path contains 'node_modules', ts considers it an external library and refuses to compile it,
+     * so we have to change the value of `isExternalLibraryImport` to false if it's true
+     * */
+    if (resolvedModule?.isExternalLibraryImport && filter(resolvedModule?.resolvedFileName)) {
+      resolvedModule.isExternalLibraryImport = false;
+    }
+    return resolvedModule;
   };
 }

packages/typescript/test/fixtures/external-library-import/main.ts

@@ -0,0 +1 @@
+export { dep } from './node_modules/dep';

packages/typescript/test/fixtures/external-library-import/tsconfig.json

@@ -0,0 +1 @@
+{}

packages/typescript/test/test.js

@@ -1393,3 +1393,12 @@ test.serial('noForceEmit option defers to tsconfig.json for noEmit', async (t) =
   const originalCode = fs.readFileSync(path.join(__dirname, input), 'utf8');
   t.is(output[0].code, originalCode);
 });
+
+test.serial('compiled external library', async (t) => {
+  const input = 'fixtures/external-library-import/main.ts';
+  await rollup({
+    input,
+    plugins: [typescript({ tsconfig: 'fixtures/external-library-import/tsconfig.json' })]
+  });
+  t.pass();
+});