feat(volume): fromJSON now accepts Buffer as volume content (#880)

This commit resolves cases when you want to inject raw binary (`Buffer`)
data into your virtual volumes. For example when you want to validate
an archive extracts files correctly.

docs/node/reference.md

@@ -71,6 +71,7 @@ vol.fromJSON(
   {
     './index.js': '...',
     './package.json': '...',
+    './index.node': new Buffer(),
   },
   '/app',
 );

src/__tests__/volume.test.ts

@@ -274,6 +274,16 @@ describe('volume', () => {
         expect(stat.isDirectory()).toBe(true);
         expect(vol.readdirSync('/dir')).toEqual([]);
       });
+
+      it('supports using buffers for file content', () => {
+        const vol = new Volume();
+        const text = 'bip-boup';
+        const buffer = Buffer.from(text, 'utf-8');
+        vol.fromJSON({ '/buffer': buffer });
+        expect(vol.toJSON()).toStrictEqual({ '/buffer': text });
+        expect(vol.readFileSync('/buffer')).toStrictEqual(buffer);
+        expect(vol.readFileSync('/buffer', 'utf-8')).toStrictEqual(text);
+      });
     });
 
     describe('.fromNestedJSON(nestedJSON[, cwd])', () => {

src/volume.ts

@@ -188,13 +188,13 @@ function validateGid(gid: number) {
 }
 
 // ---------------------------------------- Volume
-type DirectoryContent = string | null;
+type DirectoryContent = string | Buffer | null;
 
-export interface DirectoryJSON {
-  [key: string]: DirectoryContent;
+export interface DirectoryJSON<T extends DirectoryContent = DirectoryContent> {
+  [key: string]: T;
 }
-export interface NestedDirectoryJSON {
-  [key: string]: DirectoryContent | NestedDirectoryJSON;
+export interface NestedDirectoryJSON<T extends DirectoryContent = DirectoryContent> {
+  [key: string]: T | NestedDirectoryJSON;
 }
 
 function flattenJSON(nestedJSON: NestedDirectoryJSON): DirectoryJSON {
@@ -206,7 +206,7 @@ function flattenJSON(nestedJSON: NestedDirectoryJSON): DirectoryJSON {
 
       const joinedPath = join(pathPrefix, path);
 
-      if (typeof contentOrNode === 'string') {
+      if (typeof contentOrNode === 'string' || contentOrNode instanceof Buffer) {
         flatJSON[joinedPath] = contentOrNode;
       } else if (typeof contentOrNode === 'object' && contentOrNode !== null && Object.keys(contentOrNode).length > 0) {
         // empty directories need an explicit entry and therefore get handled in `else`, non-empty ones are implicitly considered
@@ -526,7 +526,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
     });
   }
 
-  private _toJSON(link = this.root, json = {}, path?: string, asBuffer?: boolean): DirectoryJSON {
+  private _toJSON(link = this.root, json = {}, path?: string, asBuffer?: boolean): DirectoryJSON<string | null> {
     let isEmpty = true;
 
     let children = link.children;
@@ -568,7 +568,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
     return json;
   }
 
-  toJSON(paths?: PathLike | PathLike[], json = {}, isRelative = false, asBuffer = false): DirectoryJSON {
+  toJSON(paths?: PathLike | PathLike[], json = {}, isRelative = false, asBuffer = false): DirectoryJSON<string | null> {
     const links: Link[] = [];
 
     if (paths) {
@@ -595,7 +595,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
 
       filename = resolve(filename, cwd);
 
-      if (typeof data === 'string') {
+      if (typeof data === 'string' || data instanceof Buffer) {
         const dir = dirname(filename);
         this.mkdirpBase(dir, MODE.DIR);