fix: don't shift output when a dependency resolves to a .ts file (#502)

Author: dsherret

mod.ts

@@ -342,6 +342,7 @@ export async function build(options: BuildOptions): Promise<void> {
   const esmOutDir = path.join(options.outDir, "esm");
   const scriptOutDir = path.join(options.outDir, "script");
   const typesOutDir = path.join(options.outDir, "types");
+  const srcOutDir = path.join(options.outDir, "src");
   const compilerScriptTarget = getCompilerScriptTarget(scriptTarget);
   // TypeScript 6.0 no longer automatically discovers the `@types` packages
   // installed in the output's node_modules, so resolve and include them
@@ -352,6 +353,10 @@ export async function build(options: BuildOptions): Promise<void> {
   const project = createProjectSync({
     compilerOptions: {
       outDir: typesOutDir,
+      // pin the root so that a dependency resolving to a file outside the
+      // sources (ex. a package that ships a .ts file) can't shift the output
+      // down a directory and leave the package.json paths dangling
+      rootDir: srcOutDir,
       allowJs: true,
       alwaysStrict: true,
       stripInternal: options.compilerOptions?.stripInternal,
@@ -588,10 +593,20 @@ export async function build(options: BuildOptions): Promise<void> {
         d.code !== 1343 &&
         // 1470: The_import_meta_meta_property_is_not_allowed_in_files_which_will_build_into_CommonJS_output
         d.code !== 1470 &&
+        !isInNodeModules(d) &&
         (options.filterDiagnostic?.(d) ?? true)
       );
     }
 
+    /** A dependency shipping a .ts file that resolution lands on is compiled
+     * as a source rather than a declaration file, so `skipLibCheck` doesn't
+     * cover it. Its code is no more the package author's problem than a .d.ts
+     * would be, so ignore it all the same. */
+    function isInNodeModules(diagnostic: ts.Diagnostic) {
+      const fileName = diagnostic.file?.fileName;
+      return fileName != null && fileName.includes("/node_modules/");
+    }
+
     function shouldTypeCheck() {
       const typeCheck = options.typeCheck!;
       switch (typeCheck) {

tests/integration.test.ts

@@ -1180,6 +1180,34 @@ Deno.test("should build undici project", async () => {
   });
 });
 
+Deno.test("should build a project with a dependency that resolves to a .ts file", async () => {
+  await runTest("node_modules_ts_project", {
+    entryPoints: ["mod.ts", "nested/other.ts"],
+    outDir: "./npm",
+    scriptModule: false,
+    declaration: "separate",
+    test: false,
+    shims: {},
+    package: {
+      name: "node-modules-ts-project",
+      version: "1.0.0",
+    },
+  }, (output) => {
+    // see issue #460 -- the dependency's own .ts file must not shift the
+    // output down a directory, which would leave the package.json paths
+    // pointing at files that don't exist
+    output.assertExists("esm/mod.js");
+    output.assertExists("esm/nested/other.js");
+    output.assertNotExists("esm/src/mod.js");
+    output.assertNotExists("esm/node_modules");
+    assertEquals(output.packageJson.module, "./esm/mod.js");
+    assertEquals(
+      output.packageJson.exports["."].import.default,
+      "./esm/mod.js",
+    );
+  });
+});
+
 Deno.test("should run the test preload module", async () => {
   await runTest("test_preload_project", {
     entryPoints: ["mod.ts"],
@@ -1453,6 +1481,7 @@ async function runTest(
     | "polyfill_promise_with_resolvers_project"
     | "polyfill_import_meta_project"
     | "module_mappings_project"
+    | "node_modules_ts_project"
     | "node_types_project"
     | "undici_project"
     | "shim_project"

tests/node_modules_ts_project/mod.ts

@@ -0,0 +1,9 @@
+// Copyright 2018-2024 the Deno authors. MIT license.
+
+// `type-detect` ships an `index.ts` that TypeScript's resolution lands on, so
+// it ends up in the program as a source file rather than a declaration file
+import typeDetect from "npm:type-detect@^4.1.0";
+
+export function detect(value: unknown): string {
+  return typeDetect(value);
+}

tests/node_modules_ts_project/nested/other.ts

@@ -0,0 +1,3 @@
+// Copyright 2018-2024 the Deno authors. MIT license.
+
+export const other = "other";