core: human friendly error for corrupt box metadata

CHANGELOG.md

@@ -22,6 +22,7 @@ BUG FIXES:
   - core: Make sure machine IDs are always strings. [GH-2434]
   - core: 100% CPU spike when waiting for SSH is fixed. [GH-2401]
   - core: Command lookup works on systems where PATH is not valid UTF-8 [GH-2514]
+  - core: Human-friendly error if box metadata.json becomes corrupted. [GH-2305]
   - guests/freebsd: Mounting NFS folders works. [GH-2400]
   - guests/freebsd: Uses `sh` by default for shell. [GH-2485]
   - guests/redhat: Down interface before messing up configuration file

lib/vagrant/box.rb

@@ -47,7 +47,12 @@ module Vagrant
 
       metadata_file = directory.join("metadata.json")
       raise Errors::BoxMetadataFileNotFound, :name => @name if !metadata_file.file?
-      @metadata = JSON.parse(directory.join("metadata.json").read)
+
+      begin
+        @metadata = JSON.parse(directory.join("metadata.json").read)
+      rescue JSON::ParserError
+        raise Errors::BoxMetadataCorrupted, name: @name
+      end
 
       @logger = Log4r::Logger.new("vagrant::box")
     end

lib/vagrant/errors.rb

@@ -124,6 +124,10 @@ module Vagrant
       error_key(:box_config_changing_box)
     end
 
+    class BoxMetadataCorrupted < VagrantError
+      error_key(:box_metadata_corrupted)
+    end
+
     class BoxMetadataFileNotFound < VagrantError
       error_key(:box_metadata_file_not_found)
     end

templates/locales/en.yml

@@ -180,6 +180,10 @@ en:
         a new box. This box, in turn, specified a different box. This isn't
         allowed, as it could lead to infinite recursion of Vagrant configuration
         loading. Please fix this.
+      box_metadata_corrupted: |-
+        The metadata associated with the box '%{name}' appears corrupted.
+        This is most often caused by a disk issue or system crash. Please
+        remove the box, re-add it, and try again.
       box_metadata_file_not_found: |-
         The "metadata.json" file for the box '%{name}' was not found.
         Boxes require this file in order for Vagrant to determine the
@@ -580,7 +584,7 @@ en:
         Port: %{port}
         Username: %{username}
         Private key: %{key_path}
-      synced_folder_unusable: |
+      synced_folder_unusable: |-
         The synced folder type '%{type}' is reporting as unusable for
         your current setup. Please verify you have all the proper
         prerequisites for using this shared folder type and try again.

test/unit/vagrant/box_test.rb

@@ -40,6 +40,19 @@ describe Vagrant::Box do
     instance.metadata.should == data
   end
 
+  context "with a corrupt metadata file" do
+    before do
+      directory.join("metadata.json").open("w") do |f|
+        f.write("")
+      end
+    end
+
+    it "should raise an exception" do
+      expect { subject }.
+        to raise_error(Vagrant::Errors::BoxMetadataCorrupted)
+    end
+  end
+
   context "without a metadata file" do
     before :each do
       directory.join("metadata.json").delete