feat: support declarationDir

Author: s-panferov

src/__test__/declaration.ts

@@ -15,6 +15,7 @@ spec(__filename, async function() {
     `);
 
     tsconfig({
+        declarationDir: 'decl',
         declaration: true
     });
 
@@ -24,11 +25,11 @@ spec(__filename, async function() {
 
     expectErrors(stats, 0);
 
-    checkOutput('src/index.d.ts', `
+    checkOutput('../decl/index.d.ts', `
         export { default as sum } from './utils/sum'
     `);
 
-    checkOutput('src/utils/sum.d.ts', `
+    checkOutput('../decl/utils/sum.d.ts', `
         export default function sum(a: number, b: number): number
     `);
 
@@ -45,11 +46,11 @@ spec(__filename, async function() {
 
     await watcher.wait();
 
-    checkOutput('src/utils/mul.d.ts', `
+    checkOutput('../decl/utils/mul.d.ts', `
         export default function mul(a: number, b: number): number
     `);
 
-    checkOutput('src/index.d.ts', `
+    checkOutput('../decl/index.d.ts', `
         export { default as sum } from './utils/sum';
         export { default as mul } from './utils/mul';
     `);

src/helpers.ts

@@ -14,7 +14,7 @@ export function toUnix(fileName: string): string {
 }
 
 function withoutExt(fileName: string): string {
-    return path.join(path.dirname(fileName), path.basename(fileName).split('.')[0]);
+    return path.basename(fileName).split('.')[0];
 }
 
 function isFileEmit(fileName, outputFileName, sourceFileName) {

src/index.ts

@@ -1,5 +1,6 @@
 import * as _ from 'lodash';
 import * as path from 'path';
+import * as fs from 'fs';
 
 import { findCompiledModule, cache } from './cache';
 import * as helpers from './helpers';
@@ -8,6 +9,7 @@ import { PathPlugin } from './paths-plugin';
 import { CheckerPlugin as _CheckerPlugin } from './watch-mode';
 
 const loaderUtils = require('loader-utils');
+const mkdirp = require('mkdirp');
 
 function loader(text) {
     try {
@@ -163,13 +165,9 @@ function transform(
         }
 
         if (emitResult.declaration) {
-            const declPath = path.relative(
-                instance.context,
-                emitResult.declaration.name
-            );
-
-            webpack.emitFile(
-                declPath,
+            mkdirp.sync(path.dirname(emitResult.declaration.name));
+            fs.writeFileSync(
+                emitResult.declaration.name,
                 emitResult.declaration.text
             );
         }

src/instance.ts

@@ -235,6 +235,7 @@ function applyDefaults(
     _.defaults(compilerConfig.options, {
         sourceMap: true,
         verbose: false,
+        declarationDir: compilerConfig.options.outDir,
         skipDefaultLibCheck: true,
         suppressOutputPathCheck: true
     });