Merge pull request #83 from reflector-six/allow-file-postprocessors

Allow file postprocessors like Prettier

Author: Quramy

README.md

@@ -143,10 +143,18 @@ Returns `DtsContent` instance.
 ### class DtsContent
 DtsContent instance has `*.d.ts` content, final output path, and function to write file.
 
-#### `writeFile() => Promise(dtsContent)`
-Writes the DtsContent instance's content to a file.
+#### `writeFile(postprocessor) => Promise(dtsContent)`
+Writes the DtsContent instance's content to a file. Returns the DtsContent instance.
 
-* `dtsContent`: the DtsContent instance itself.
+* `postprocessor` (optional): a function that takes the formatted definition string and returns a modified string that will be the final content written to the file.
+
+  You could use this, for example, to pass generated definitions through a formatter like Prettier, or to add a comment to the top of generated files:
+
+  ```js
+  dtsContent.writeFile(
+    definition => `// Generated automatically, do not edit\n${definition}`
+  )
+  ```
 
 #### `tokens`
 An array of tokens retrieved from input CSS file.

src/dts-content.ts

@@ -68,13 +68,15 @@ export class DtsContent {
         return path.join(this.rootDir, this.searchDir, this.rInputPath);
     }
 
-    public async writeFile(): Promise<void> {
+    public async writeFile(postprocessor = (formatted: string) => formatted): Promise<void> {
+        const finalOutput = postprocessor(this.formatted);
+
         const outPathDir = path.dirname(this.outputFilePath);
         if(!isThere(outPathDir)) {
             mkdirp.sync(outPathDir);
         }
 
-        await writeFile(this.outputFilePath, this.formatted, 'utf8');
+        await writeFile(this.outputFilePath, finalOutput, 'utf8');
     }
 }
 

test/dts-creator.spec.ts

@@ -180,6 +180,19 @@ export = styles;
   });
 
   describe('#writeFile', () => {
+    it('accepts a postprocessor function', done => {
+      new DtsCreator()
+        .create('test/testStyle.css')
+        .then(content => {
+          return content.writeFile(
+            formatted => `// this banner was added to the .d.ts file automatically.\n${formatted}`
+          );
+        })
+        .then(() => {
+          done();
+        });
+    });
+
     it('writes a file', done => {
       new DtsCreator()
         .create('test/testStyle.css')