fix: ignore high mode bits passed to constructor (#53)

The UnixFS Spec [says](https://github.com/ipfs/specs/blob/master/UNIXFS.md#metadata) high mode bits not defined in the version of the spec supported by a given implementation should be ignored but also persisted to ensure forwards compatibility.  The change here:

1. Ignores high bits passed to the constructor
1. Respects high bits read out of a protobuf though does not expose them
1. Writes high bits back to a protobuf but only if they were read from a protobuf to begin with

Author: achingbrain

packages/ipfs-unixfs-exporter/package.json

@@ -36,7 +36,7 @@
   "homepage": "https://github.com/ipfs/js-ipfs-unixfs#readme",
   "devDependencies": {
     "abort-controller": "^3.0.0",
-    "aegir": "^21.9.0",
+    "aegir": "^22.0.0",
     "chai": "^4.2.0",
     "chai-as-promised": "^7.1.1",
     "detect-node": "^2.0.4",

packages/ipfs-unixfs-importer/package.json

@@ -35,7 +35,7 @@
   },
   "homepage": "https://github.com/ipfs/js-ipfs-unixfs#readme",
   "devDependencies": {
-    "aegir": "^21.9.0",
+    "aegir": "^22.0.0",
     "chai": "^4.2.0",
     "cids": "^0.8.0",
     "detect-node": "^2.0.4",

packages/ipfs-unixfs/package.json

@@ -35,7 +35,7 @@
   },
   "homepage": "https://github.com/ipfs/js-ipfs-unixfs#readme",
   "devDependencies": {
-    "aegir": "^21.9.0",
+    "aegir": "^22.0.0",
     "chai": "^4.2.0",
     "dirty-chai": "^2.0.1",
     "nyc": "^15.0.0"

packages/ipfs-unixfs/src/index.js

@@ -129,13 +129,18 @@ class Data {
   static unmarshal (marshaled) {
     const decoded = unixfsData.decode(marshaled)
 
-    return new Data({
+    const data = new Data({
       type: types[decoded.Type],
       data: decoded.hasData() ? decoded.Data : undefined,
       blockSizes: decoded.blocksizes,
       mode: decoded.hasMode() ? decoded.mode : undefined,
       mtime: decoded.hasMtime() ? decoded.mtime : undefined
     })
+
+    // make sure we honor the original mode
+    data._originalMode = decoded.hasMode() ? decoded.mode : undefined
+
+    return data
   }
 
   constructor (...args) {
@@ -158,7 +163,6 @@ class Data {
     this.hashType = hashType
     this.fanout = fanout
     this.blockSizes = blockSizes || []
-    this._originalMode = mode
 
     const parsedMode = parseMode(mode)
 

packages/ipfs-unixfs/test/unixfs-format.spec.js

@@ -331,6 +331,67 @@ describe('unixfs-format', () => {
     expect(entry).to.have.property('mode', mode)
   })
 
+  it('omits default file mode from protobuf', () => {
+    const entry = new UnixFS({
+      type: 'file',
+      mode: 0o644
+    })
+
+    const marshaled = entry.marshal()
+
+    const protobuf = unixfsData.decode(marshaled)
+    expect(protobuf.hasMode()).to.be.false()
+  })
+
+  it('omits default directory mode from protobuf', () => {
+    const entry = new UnixFS({
+      type: 'directory',
+      mode: 0o755
+    })
+
+    const marshaled = entry.marshal()
+
+    const protobuf = unixfsData.decode(marshaled)
+    expect(protobuf.hasMode()).to.be.false()
+  })
+
+  it('respects high bits in mode read from buffer', () => {
+    const mode = 0o0100644 // similar to output from fs.stat
+    const buf = unixfsData.encode({
+      Type: unixfsData.DataType.File,
+      mode
+    })
+
+    const entry = UnixFS.unmarshal(buf)
+
+    // should have truncated mode to bits in the version of the spec this module supports
+    expect(entry).to.have.property('mode', 0o644)
+
+    const marshaled = entry.marshal()
+
+    const protobuf = unixfsData.decode(marshaled)
+    expect(protobuf).to.have.property('mode', mode)
+  })
+
+  it('ignores high bits in mode passed to constructor', () => {
+    const mode = 0o0100644 // similar to output from fs.stat
+    const entry = new UnixFS({
+      type: 'file',
+      mode
+    })
+
+    // should have truncated mode to bits in the version of the spec this module supports
+    expect(entry).to.have.property('mode', 0o644)
+
+    const marshaled = entry.marshal()
+    const unmarshaled = UnixFS.unmarshal(marshaled)
+
+    expect(unmarshaled).to.have.property('mode', 0o644)
+
+    const protobuf = unixfsData.decode(marshaled)
+    expect(protobuf.hasMode()).to.be.false()
+  })
+
   // figuring out what is this metadata for https://github.com/ipfs/js-ipfs-data-importing/issues/3#issuecomment-182336526
   it('metadata', () => {
     const entry = new UnixFS({