fix: get block with empty data (#789)

* Fix for empty data in block.

Found this very strange bug when creating DAGNode's with empty buffers for data.

streamToValue returns an empty array when the data is empty, which down the line triggers an exception in ipfs-block because this sends an empty array instead of a buffer.

* fix: get empty block for response without X-Stream-Output

js-ipfs currently does not set the X-Stream-Output header on block.get responses so we also need a check for an empty array on our buffered res.

License: MIT
Signed-off-by: Alan Shaw <alan@tableflip.io>

* chore: update to latest interface-ipfs-core

License: MIT
Signed-off-by: Alan Shaw <alan@tableflip.io>

package.json

@@ -79,7 +79,7 @@
     "eslint-plugin-react": "^7.9.1",
     "go-ipfs-dep": "~0.4.15",
     "gulp": "^3.9.1",
-    "interface-ipfs-core": "~0.68.1",
+    "interface-ipfs-core": "~0.69.0",
     "ipfsd-ctl": "~0.37.3",
     "pull-stream": "^3.6.8",
     "socket.io": "^2.1.1",

src/block/get.js

@@ -34,11 +34,18 @@ module.exports = (send) => {
     const transform = (res, callback) => {
       if (Buffer.isBuffer(res)) {
         callback(null, new Block(res, cid))
+      // For empty blocks, concat-stream can't infer the encoding so we are
+      // passed back an empty array
+      } else if (Array.isArray(res) && res.length === 0) {
+        callback(null, new Block(Buffer.alloc(0), cid))
       } else {
         streamToValue(res, (err, data) => {
           if (err) {
             return callback(err)
           }
+          // For empty blocks, concat-stream can't infer the encoding so we are
+          // passed back an empty array
+          if (!data.length) data = Buffer.alloc(0)
           callback(null, new Block(data, cid))
         })
       }