fix(typescript): emit declaration files for type-only source files that are not explicitly included

packages/typescript/src/index.ts

@@ -12,7 +12,13 @@ import createModuleResolver from './moduleResolution';
 import { getPluginOptions } from './options/plugin';
 import { emitParsedOptionsErrors, parseTypescriptConfig } from './options/tsconfig';
 import { validatePaths, validateSourceMap } from './options/validate';
-import findTypescriptOutput, { getEmittedFile, normalizePath, emitFile } from './outputFile';
+import findTypescriptOutput, {
+  getEmittedFile,
+  normalizePath,
+  emitFile,
+  isDeclarationOutputFile,
+  isMapOutputFile
+} from './outputFile';
 import { preflight } from './preflight';
 import createWatchProgram, { WatchProgramHelper } from './watchProgram';
 import TSCache from './tscache';
@@ -150,40 +156,41 @@ export default function typescript(options: RollupTypescriptOptions = {}): Plugi
     },
 
     async generateBundle(outputOptions) {
-      parsedOptions.fileNames.forEach((fileName) => {
-        const output = findTypescriptOutput(ts, parsedOptions, fileName, emittedFiles, tsCache);
-        output.declarations.forEach((id) => {
-          const code = getEmittedFile(id, emittedFiles, tsCache);
-          if (!code || !parsedOptions.options.declaration) {
-            return;
-          }
-
-          let baseDir: string | undefined;
-          if (outputOptions.dir) {
-            baseDir = outputOptions.dir;
-          } else if (outputOptions.file) {
-            // find common path of output.file and configured declation output
-            const outputDir = path.dirname(outputOptions.file);
-            const configured = path.resolve(
-              parsedOptions.options.declarationDir ||
-                parsedOptions.options.outDir ||
-                tsconfig ||
-                process.cwd()
-            );
-            const backwards = path
-              .relative(outputDir, configured)
-              .split(path.sep)
-              .filter((v) => v === '..')
-              .join(path.sep);
-            baseDir = path.normalize(`${outputDir}/${backwards}`);
-          }
-          if (!baseDir) return;
-
-          this.emitFile({
-            type: 'asset',
-            fileName: normalizePath(path.relative(baseDir, id)),
-            source: code
-          });
+      const declarationAndMapFiles = [...emittedFiles.keys()].filter(
+        (fileName) => isDeclarationOutputFile(fileName) || isMapOutputFile(fileName)
+      );
+
+      declarationAndMapFiles.forEach((id) => {
+        const code = getEmittedFile(id, emittedFiles, tsCache);
+        if (!code || !parsedOptions.options.declaration) {
+          return;
+        }
+
+        let baseDir: string | undefined;
+        if (outputOptions.dir) {
+          baseDir = outputOptions.dir;
+        } else if (outputOptions.file) {
+          // find common path of output.file and configured declation output
+          const outputDir = path.dirname(outputOptions.file);
+          const configured = path.resolve(
+            parsedOptions.options.declarationDir ||
+              parsedOptions.options.outDir ||
+              tsconfig ||
+              process.cwd()
+          );
+          const backwards = path
+            .relative(outputDir, configured)
+            .split(path.sep)
+            .filter((v) => v === '..')
+            .join(path.sep);
+          baseDir = path.normalize(`${outputDir}/${backwards}`);
+        }
+        if (!baseDir) return;
+
+        this.emitFile({
+          type: 'asset',
+          fileName: normalizePath(path.relative(baseDir, id)),
+          source: code
         });
       });
 

packages/typescript/src/outputFile.ts

@@ -16,15 +16,22 @@ export interface TypescriptSourceDescription extends Partial<SourceDescription>
 /**
  * Checks if the given OutputFile represents some code
  */
-function isCodeOutputFile(name: string): boolean {
-  return !isMapOutputFile(name) && !name.endsWith('.d.ts');
+export function isCodeOutputFile(name: string): boolean {
+  return !isMapOutputFile(name) && !isDeclarationOutputFile(name);
 }
 
 /**
  * Checks if the given OutputFile represents some source map
  */
-function isMapOutputFile(name: string): boolean {
-  return name.endsWith('.map');
+export function isMapOutputFile(name: string): boolean {
+  return name.endsWith('ts.map');
+}
+
+/**
+ * Checks if the given OutputFile represents some declaration
+ */
+export function isDeclarationOutputFile(name: string): boolean {
+  return /\.d\.[cm]?ts$/.test(name);
 }
 
 /**

packages/typescript/test/declarations.ts

@@ -48,11 +48,11 @@ test.serial('supports creating declaration files in subfolder', async (t) => {
     onwarn
   });
   const output = await getCode(bundle, { format: 'es', dir: 'fixtures/basic/dist' }, true);
-  const declaration = output[1].source as string;
+  const declaration = output[2].source as string;
 
   t.deepEqual(
     output.map((out) => out.fileName),
-    ['main.js', 'types/main.d.ts', 'types/main.d.ts.map']
+    ['main.js', 'types/main.d.ts.map', 'types/main.d.ts']
   );
 
   t.true(declaration.includes('declare const answer = 42;'), declaration);
@@ -100,23 +100,54 @@ test.serial('supports creating declaration files for interface only source file'
     { format: 'es', dir: 'fixtures/export-interface-only/dist' },
     true
   );
-  const declaration = output[1].source as string;
+  const declaration = output[2].source as string;
 
   t.deepEqual(
     output.map((out) => out.fileName),
     [
       'main.js',
-      'types/interface.d.ts',
       'types/interface.d.ts.map',
-      'types/main.d.ts',
-      'types/main.d.ts.map'
+      'types/interface.d.ts',
+      'types/main.d.ts.map',
+      'types/main.d.ts'
     ]
   );
 
   t.true(declaration.includes('export interface ITest'), declaration);
   t.true(declaration.includes('//# sourceMappingURL=interface.d.ts.map'), declaration);
 });
 
+test.serial(
+  'supports creating declaration files for type-only source files that are implicitly included',
+  async (t) => {
+    const bundle = await rollup({
+      input: 'fixtures/implicitly-included-type-only-file/main.ts',
+      plugins: [
+        typescript({
+          tsconfig: 'fixtures/implicitly-included-type-only-file/tsconfig.json',
+          declarationDir: 'fixtures/implicitly-included-type-only-file/dist/types',
+          declaration: true
+        }),
+        onwarn
+      ]
+    });
+    const output = await getCode(
+      bundle,
+      { format: 'es', dir: 'fixtures/implicitly-included-type-only-file/dist' },
+      true
+    );
+    const declaration = output[1].source as string;
+
+    t.deepEqual(
+      output.map((out) => out.fileName),
+      // 'types/should-not-be-emitted-types.d.ts' should not be emitted because 'main.ts' does not import/export from it.
+      ['main.js', 'types/should-be-emitted-types.d.ts', 'types/main.d.ts']
+    );
+
+    t.true(declaration.includes('export declare type MyNumber = number;'), declaration);
+  }
+);
+
 test.serial('supports creating declaration files in declarationDir', async (t) => {
   const bundle = await rollup({
     input: 'fixtures/basic/main.ts',

packages/typescript/test/fixtures/implicitly-included-type-only-file/main.ts

@@ -0,0 +1 @@
+export { MyNumber } from './should-be-emitted-types';

packages/typescript/test/fixtures/implicitly-included-type-only-file/should-be-emitted-types.ts

@@ -0,0 +1 @@
+export type MyNumber = number;

packages/typescript/test/fixtures/implicitly-included-type-only-file/should-not-be-emitted-types.ts

@@ -0,0 +1,2 @@
+// This file is intentionally not imported from.
+export type MyString = string;

packages/typescript/test/fixtures/implicitly-included-type-only-file/tsconfig.json

@@ -0,0 +1,3 @@
+{
+  "include": ["main.ts"]
+}