[CHEF-3863] improve error compat with old impl.

1 files changed, 17 insertions, 3 deletions

diff --git a/lib/chef/json_compat.rb b/lib/chef/json_compat.rb
index 80afc163e7..e8f8a75162 100644
--- a/lib/chef/json_compat.rb
+++ b/lib/chef/json_compat.rb
@@ -38,6 +38,7 @@ class Chef
     CHEF_RESOURCECOLLECTION = "Chef::ResourceCollection".freeze
 
     class <<self
+
       # See CHEF-1292/PL-538. Increase the max nesting for JSON, which defaults
       # to 19, and isn't enough for some (for example, a Node within a Node)
       # structures.
@@ -53,6 +54,13 @@ class Chef
       def from_json(source, opts = {})
         obj = ::Yajl::Parser.parse(source)
 
+        # JSON gem requires top level object to be a Hash or Array (otherwise
+        # you get the "must contain two octets" error). Yajl doesn't impose the
+        # same limitation. For compatibility, we re-impose this condition.
+        unless obj.kind_of?(Hash) or obj.kind_of?(Array)
+          raise JSON::ParserError, "Top level JSON object must be a Hash or Array. (actual: #{obj.class})"
+        end
+
         # The old default in the json gem (which we are mimicing because we
         # sadly rely on this misfeature) is to "create additions" i.e., convert
         # JSON objects into ruby objects. Explicit :create_additions => false
@@ -67,7 +75,7 @@ class Chef
       # Look at an object that's a basic type (from json parse) and convert it
       # to an instance of Chef classes if desired.
       def map_to_rb_obj(json_obj)
-        res = case json_obj
+        case json_obj
         when Hash
           mapped_hash = map_hash_to_rb_obj(json_obj)
           if json_obj.has_key?(JSON_CLASS) && (class_to_inflate = class_for_json_class(json_obj[JSON_CLASS]))
@@ -80,7 +88,6 @@ class Chef
         else
           json_obj
         end
-        res
       end
 
       def map_hash_to_rb_obj(json_hash)
@@ -99,6 +106,10 @@ class Chef
       end
 
 
+      # Map +json_class+ to a Class object. We use a +case+ instead of a Hash
+      # assigned to a constant because otherwise this file could not be loaded
+      # until all the constants were defined, which means you'd have to load
+      # the world to get json, which would make knife very slow.
       def class_for_json_class(json_class)
         case json_class
         when CHEF_APICLIENT
@@ -116,6 +127,9 @@ class Chef
         when CHEF_ROLE
           Chef::Role
         when CHEF_SANDBOX
+          # a falsey return here will disable object inflation/"create
+          # additions" in the caller. In Chef 11 this is correct, we just have
+          # a dummy Chef::Sandbox class for compat with Chef 10 servers.
           false
         when CHEF_RESOURCE
           Chef::Resource
@@ -124,7 +138,7 @@ class Chef
         when /^Chef::Resource/
           Chef::Resource.find_subclass_by_name(json_class)
         else
-          raise ArgumentError, "Unsupported `json_class` type '#{json_class}'"
+          raise JSON::ParserError, "Unsupported `json_class` type '#{json_class}'"
         end
       end