write out DTS file structure

README.md

@@ -71,7 +71,12 @@ Plugin takes following options:
 
 * `rollupCommonJSResolveHack`: false
 
-	On windows typescript resolver favors POSIX path, while commonjs plugin (and maybe others?) uses native path as module id. This can result in `namedExports` being ignored if rollup happened to use typescript's resolution. Set to true to pass resolved module path through `resolve()` to match up with `rollup-plugin-commonjs`. 
+	On windows typescript resolver favors POSIX path, while commonjs plugin (and maybe others?) uses native path as module id. This can result in `namedExports` being ignored if rollup happened to use typescript's resolution. Set to true to pass resolved module path through `resolve()` to match up with `rollup-plugin-commonjs`.
+
+### Declarations
+
+This plugin respects `declaration: true` in your `tsconfig.json` file. When set, it will emit `*.d.ts` files for your bundle. The resulting file(s) can then be used with the `types`
+property in your `package.json` file as described [here](https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html).
 
 ### Watch mode
 

src/index.ts

@@ -152,6 +152,8 @@ export default function typescript(options: IOptions)
 
 	let noErrors = true;
 
+	const declarations: ts.OutputFile[] = [];
+
 	// printing compiler option errors
 	if (options.check)
 		printDiagnostics(context, convertDiagnostic("options", service.getCompilerOptionsDiagnostics()));
@@ -249,10 +251,12 @@ export default function typescript(options: IOptions)
 
 				const transpiled = _.find(output.outputFiles, (entry) => _.endsWith(entry.name, ".js") );
 				const map = _.find(output.outputFiles, (entry) => _.endsWith(entry.name, ".map") );
+				const dts = _.find(output.outputFiles, (entry) => _.endsWith(entry.name, ".d.ts"));
 
 				return {
 					code: transpiled ? transpiled.text : undefined,
 					map: map ? JSON.parse(map.text) : { mappings: "" },
+					dts,
 				};
 			});
 
@@ -275,6 +279,10 @@ export default function typescript(options: IOptions)
 				printDiagnostics(contextWrapper, diagnostics);
 			}
 
+			if (result && result.dts) {
+				declarations.push(result.dts);
+			}
+
 			return result;
 		},
 
@@ -311,5 +319,11 @@ export default function typescript(options: IOptions)
 
 			round++;
 		},
+
+		onwrite() {
+			declarations.forEach(({ name, text, writeByteOrderMark }) => {
+				ts.sys.writeFile(name, text, writeByteOrderMark);
+			});
+		},
 	};
 }

src/tscache.ts

@@ -12,6 +12,7 @@ export interface ICode
 {
 	code: string | undefined;
 	map: string | undefined;
+	dts?: ts.OutputFile | undefined;
 }
 
 interface INodeLabel