fix: allow setting custom file types beyond S_IFREG and S_IFDIR (#1082)

Prior to this change, the `mode` argument to `Node` and `Volume`
was only used to set the file permissions.

src/__tests__/node.test.ts

@@ -5,7 +5,7 @@ describe('node.ts', () => {
   describe('Node', () => {
     const node = new Node(1);
     it('properly sets mode with permission respected', () => {
-      const node = new Node(1, 0o755);
+      const node = new Node(1, constants.S_IFREG | 0o755);
       expect(node.perm).toBe(0o755);
       expect(node.mode).toBe(constants.S_IFREG | 0o755);
       expect(node.isFile()).toBe(true); // Make sure we still know it's a file
@@ -72,7 +72,7 @@ describe('node.ts', () => {
       });
     });
     describe('.chmod(perm)', () => {
-      const node = new Node(1);
+      const node = new Node(1, constants.S_IFREG | 0o666);
       expect(node.perm).toBe(0o666);
       expect(node.isFile()).toBe(true);
       node.chmod(0o600);

src/__tests__/volume.test.ts

@@ -447,6 +447,15 @@ describe('volume', () => {
           done();
         });
       });
+      it('Creates a character device at root (/null)', done => {
+        vol.open('/null', 'w', constants.S_IFCHR | 0o666, (err, fd) => {
+          expect(err).toBe(null);
+          expect(vol.root.getChild('null')?.getNode().isCharacterDevice()).toBe(true);
+          expect(typeof fd).toBe('number');
+          expect(fd).toBeGreaterThan(0);
+          done();
+        });
+      }, 100);
       it('Error on file not found', done => {
         vol.open('/non-existing-file.txt', 'r', (err, fd) => {
           expect(err).toHaveProperty('code', 'ENOENT');

src/node.ts

@@ -5,7 +5,7 @@ import { Volume } from './volume';
 import { EventEmitter } from 'events';
 import Stats from './Stats';
 
-const { S_IFMT, S_IFDIR, S_IFREG, S_IFLNK, O_APPEND } = constants;
+const { S_IFMT, S_IFDIR, S_IFREG, S_IFLNK, S_IFCHR, O_APPEND } = constants;
 const getuid = (): number => process.getuid?.() ?? 0;
 const getgid = (): number => process.getgid?.() ?? 0;
 
@@ -29,20 +29,17 @@ export class Node extends EventEmitter {
   // data: string = '';
   buf: Buffer;
 
-  private _perm = 0o666; // Permissions `chmod`, `fchmod`
-
-  mode = S_IFREG; // S_IFDIR, S_IFREG, etc.. (file by default?)
+  mode: number; // S_IFDIR, S_IFREG, etc..
 
   // Number of hard links pointing at this Node.
   private _nlink = 1;
 
   // Path to another node, if this is a symlink.
   symlink: string;
 
-  constructor(ino: number, perm: number = 0o666) {
+  constructor(ino: number, mode: number = 0o666) {
     super();
-    this._perm = perm;
-    this.mode |= perm;
+    this.mode = mode;
     this.ino = ino;
   }
 
@@ -90,13 +87,13 @@ export class Node extends EventEmitter {
     return this._mtime;
   }
 
-  public set perm(perm: number) {
-    this._perm = perm;
-    this.ctime = new Date();
+  public get perm(): number {
+    return this.mode & ~S_IFMT;
   }
 
-  public get perm(): number {
-    return this._perm;
+  public set perm(perm: number) {
+    this.mode = (this.mode & S_IFMT) | (perm & ~S_IFMT);
+    this.ctime = new Date();
   }
 
   public set nlink(nlink: number) {
@@ -135,19 +132,7 @@ export class Node extends EventEmitter {
   }
 
   setModeProperty(property: number) {
-    this.mode = (this.mode & ~S_IFMT) | property;
-  }
-
-  setIsFile() {
-    this.setModeProperty(S_IFREG);
-  }
-
-  setIsDirectory() {
-    this.setModeProperty(S_IFDIR);
-  }
-
-  setIsSymlink() {
-    this.setModeProperty(S_IFLNK);
+    this.mode = property;
   }
 
   isFile() {
@@ -163,8 +148,12 @@ export class Node extends EventEmitter {
     return (this.mode & S_IFMT) === S_IFLNK;
   }
 
+  isCharacterDevice() {
+    return (this.mode & S_IFMT) === S_IFCHR;
+  }
+
   makeSymlink(symlink: string) {
-    this.mode = S_IFLNK;
+    this.mode = S_IFLNK | 0o666;
     this.symlink = symlink;
   }
 
@@ -223,8 +212,7 @@ export class Node extends EventEmitter {
   }
 
   chmod(perm: number) {
-    this.perm = perm;
-    this.mode = (this.mode & ~0o777) | perm;
+    this.mode = (this.mode & S_IFMT) | (perm & ~S_IFMT);
     this.touch();
   }
 
@@ -376,7 +364,7 @@ export class Link extends EventEmitter {
     return this.node;
   }
 
-  createChild(name: string, node: Node = this.vol.createNode()): Link {
+  createChild(name: string, node: Node = this.vol.createNode(S_IFREG | 0o666)): Link {
     const link = new Link(this.vol, this, name);
     link.setNode(node);
 

src/volume.ts

@@ -309,7 +309,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
     this.props = Object.assign({ Node, Link, File }, props);
 
     const root = this.createLink();
-    root.setNode(this.createNode(true));
+    root.setNode(this.createNode(constants.S_IFDIR | 0o777));
 
     const self = this; // tslint:disable-line no-this-assignment
 
@@ -349,8 +349,8 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
   }
 
   createLink(): Link;
-  createLink(parent: Link, name: string, isDirectory?: boolean, perm?: number): Link;
-  createLink(parent?: Link, name?: string, isDirectory: boolean = false, perm?: number): Link {
+  createLink(parent: Link, name: string, isDirectory?: boolean, mode?: number): Link;
+  createLink(parent?: Link, name?: string, isDirectory: boolean = false, mode?: number): Link {
     if (!parent) {
       return new this.props.Link(this, null, '');
     }
@@ -359,7 +359,14 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
       throw new Error('createLink: name cannot be empty');
     }
 
-    return parent.createChild(name, this.createNode(isDirectory, perm));
+    // If no explicit permission is provided, use defaults based on type
+    const finalPerm = mode ?? (isDirectory ? 0o777 : 0o666);
+    // To prevent making a breaking change, `mode` can also just be a permission number
+    // and the file type is set based on `isDirectory`
+    const hasFileType = mode && mode & constants.S_IFMT;
+    const modeType = hasFileType ? mode & constants.S_IFMT : isDirectory ? constants.S_IFDIR : constants.S_IFREG;
+    const finalMode = (finalPerm & ~constants.S_IFMT) | modeType;
+    return parent.createChild(name, this.createNode(finalMode));
   }
 
   deleteLink(link: Link): boolean {
@@ -387,10 +394,8 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
     return typeof releasedFd === 'number' ? releasedFd : Volume.fd--;
   }
 
-  createNode(isDirectory: boolean = false, perm?: number): Node {
-    perm ??= isDirectory ? 0o777 : 0o666;
-    const node = new this.props.Node(this.newInoNumber(), perm);
-    if (isDirectory) node.setIsDirectory();
+  createNode(mode: number): Node {
+    const node = new this.props.Node(this.newInoNumber(), mode);
     this.inodes[node.ino] = node;
     return node;
   }
@@ -685,7 +690,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
     this.openFiles = 0;
 
     this.root = this.createLink();
-    this.root.setNode(this.createNode(true));
+    this.root.setNode(this.createNode(constants.S_IFDIR | 0o777));
   }
 
   // Legacy interface
@@ -1798,7 +1803,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
     const node = dir.getNode();
     if (!node.canWrite() || !node.canExecute()) throw createError(EACCES, 'mkdir', filename);
 
-    dir.createChild(name, this.createNode(true, modeNum));
+    dir.createChild(name, this.createNode(constants.S_IFDIR | modeNum));
   }
 
   /**
@@ -1836,7 +1841,7 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
       }
 
       created = true;
-      curr = curr.createChild(steps[i], this.createNode(true, modeNum));
+      curr = curr.createChild(steps[i], this.createNode(constants.S_IFDIR | modeNum));
     }
     return created ? filename : undefined;
   }