fix(typescript): add composite to validation checks (#618)

Author: dummdidumm

packages/typescript/src/options/validate.ts

@@ -83,7 +83,7 @@ export function validatePaths(
     }
   }
 
-  if (compilerOptions.declaration || compilerOptions.declarationMap) {
+  if (compilerOptions.declaration || compilerOptions.declarationMap || compilerOptions.composite) {
     if (DIRECTORY_PROPS.every((dirProperty) => !compilerOptions[dirProperty])) {
       context.error(
         `@rollup/plugin-typescript: 'outDir' or 'declarationDir' must be specified to generate declaration files.`

packages/typescript/test/test.js

@@ -162,13 +162,13 @@ test.serial('supports creating declaration files in declarationDir', async (t) =
   t.true(output[1].source.includes('declare const answer = 42;'), output[1].source);
 });
 
-test.serial('ensures outDir is set when creating declaration files', async (t) => {
+async function ensureOutDirWhenCreatingDeclarationFiles(t, compilerOptionName) {
   const bundle = await rollup({
     input: 'fixtures/basic/main.ts',
     plugins: [
       typescript({
         tsconfig: 'fixtures/basic/tsconfig.json',
-        declaration: true
+        [compilerOptionName]: true
       })
     ],
     onwarn
@@ -183,6 +183,14 @@ test.serial('ensures outDir is set when creating declaration files', async (t) =
     ),
     `Unexpected error message: ${caughtError.message}`
   );
+}
+
+test.serial('ensures outDir is set when creating declaration files (declaration)', async (t) => {
+  await ensureOutDirWhenCreatingDeclarationFiles(t, 'declaration');
+});
+
+test.serial('ensures outDir is set when creating declaration files (composite)', async (t) => {
+  await ensureOutDirWhenCreatingDeclarationFiles(t, 'composite');
 });
 
 test.serial('ensures outDir is located in Rollup output dir', async (t) => {