importing multiple roots yields an error

Author: pgte

src/builder/create-build-stream.js

@@ -14,12 +14,11 @@ module.exports = function createBuildStream (createStrategy, ipldResolver, flush
     options.highWaterMark,
     (err) => {
       if (err) {
-        return source.end(err)
+        source.end(err)
+        return // early
       }
 
-      flushTree(files, ipldResolver, source, () => {
-        source.end()
-      })
+      flushTree(files, ipldResolver, source, source.end)
     }
   )
 

src/importer/flush-tree.js

@@ -13,6 +13,11 @@ module.exports = (files, ipldResolver, source, callback) => {
   // 1) convert files to a tree
   const fileTree = createTree(files)
 
+  if (Object.keys(fileTree).length > 1) {
+    callback(new Error('detected more than one root'))
+    return
+  }
+
   if (Object.keys(fileTree).length === 0) {
     return callback()// no dirs to be created
   }

test/test-importer.js

@@ -170,7 +170,7 @@ module.exports = (repo) => {
         ipldResolver = new IPLDResolver(bs)
       })
 
-      it('bad input', (done) => {
+      it('fails on bad input', (done) => {
         pull(
           pull.values([{
             path: '200Bytes.txt',
@@ -184,6 +184,27 @@ module.exports = (repo) => {
         )
       })
 
+      it('fails on more than one root', (done) => {
+        pull(
+          pull.values([
+            {
+              path: '/beep/200Bytes.txt',
+              content: pull.values([smallFile])
+            },
+            {
+              path: '/boop/200Bytes.txt',
+              content: pull.values([smallFile])
+            }
+          ]),
+          importer(ipldResolver, options),
+          pull.onEnd((err) => {
+            expect(err).to.exist
+            expect(err.message).to.be.eql('detected more than one root')
+            done()
+          })
+        )
+      })
+
       it('small file (smaller than a chunk)', (done) => {
         pull(
           pull.values([{