Attach URI to Read Error

When getting a `404` or `500` error it was impossible to know which
file was causing the problem with a schema that had many external
references.  This attaches the uri that failed to the error if it's
an OpenURI error, which makes is easy to know what refrenced file
was the culprit.

CHANGELOG.md

@@ -16,6 +16,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 - Made all `validate*` methods on `JSON::Validator` ultimately call `validate!`
 - Updated addressable dependency to 2.4.0
+- Attached failed `uri` or `pathname` to read errors for more meaning
 
 ## [2.6.2] - 2016-05-13
 

CONTRIBUTORS.md

@@ -32,3 +32,4 @@ CONTRIBUTORS
 * Ben Kirzhner - @benkirzhner
 * RST-J - @RST-J
 * Christian Treppo - @treppo
+* Benjamin Falk - @benfalk

lib/json-schema/schema/reader.rb

@@ -3,9 +3,8 @@
 
 module JSON
   class Schema
-    # Raised by {JSON::Schema::Reader} when one of its settings indicate
-    # a schema should not be readed.
-    class ReadRefused < StandardError
+    # Base for any reading exceptions encountered by {JSON::Schema::Reader}
+    class ReadError < StandardError
       # @return [String] the requested schema location which was refused
       attr_reader :location
 
@@ -15,7 +14,30 @@ class ReadRefused < StandardError
       def initialize(location, type)
         @location = location
         @type = type
-        super("Read of #{type == :uri ? 'URI' : type} at #{location} refused!")
+        super(error_message)
+      end
+
+      private
+
+      def type_string
+        type == :uri ? 'URI' : type.to_s
+      end
+    end
+
+    # Raised by {JSON::Schema::Reader} when one of its settings indicate
+    # a schema should not be read.
+    class ReadRefused < ReadError
+      private
+      def error_message
+        "Read of #{type_string} at #{location} refused"
+      end
+    end
+
+    # Raised by {JSON::Schema::Reader} when an attempt to read a schema fails
+    class ReadFailed < ReadError
+      private
+      def error_message
+        "Read of #{type_string} at #{location} failed"
       end
     end
 
@@ -58,6 +80,8 @@ def initialize(options = {})
       # @raise [JSON::Schema::ReadRefused] if +accept_uri+ or +accept_file+
       #   indicated the schema could not be read
       # @raise [JSON::Schema::ParseError] if the schema was not a valid JSON object
+      # @raise [JSON::Schema::ReadFailed] if reading the location was acceptable but the
+      #   attempt to retrieve it failed
       def read(location)
         uri  = JSON::Util::URI.parse(location.to_s)
         body = if uri.scheme.nil? || uri.scheme == 'file'
@@ -98,6 +122,8 @@ def read_uri(uri)
         else
           raise JSON::Schema::ReadRefused.new(uri.to_s, :uri)
         end
+      rescue OpenURI::HTTPError, SocketError
+        raise JSON::Schema::ReadFailed.new(uri.to_s, :uri)
       end
 
       def read_file(pathname)
@@ -106,6 +132,8 @@ def read_file(pathname)
         else
           raise JSON::Schema::ReadRefused.new(pathname.to_s, :file)
         end
+      rescue Errno::ENOENT
+        raise JSON::Schema::ReadFailed.new(pathname.to_s, :file)
       end
     end
   end

test/bad_schema_ref_test.rb

@@ -19,9 +19,15 @@ def test_bad_uri_ref
     }
 
     data = [1,2,3]
-    assert_raises(Errno::ENOENT) do
+    error = assert_raises(JSON::Schema::ReadFailed) do
       JSON::Validator.validate(schema,data)
     end
+
+    expanded_path = File.expand_path("../../google.json", __FILE__)
+
+    assert_equal(:file, error.type)
+    assert_equal(expanded_path, error.location)
+    assert_equal("Read of file at #{expanded_path} failed", error.message)
   end
 
   def test_bad_host_ref
@@ -32,8 +38,12 @@ def test_bad_host_ref
     }
 
     data = [1,2,3]
-    assert_raises(SocketError, OpenURI::HTTPError) do
+    error = assert_raises(JSON::Schema::ReadFailed) do
       JSON::Validator.validate(schema,data)
     end
+
+    assert_equal(:uri, error.type)
+    assert_equal("http://ppcheesecheseunicornnuuuurrrrr.example.invalid/json.schema", error.location)
+    assert_equal("Read of URI at http://ppcheesecheseunicornnuuuurrrrr.example.invalid/json.schema failed", error.message)
   end
 end

test/schema_reader_test.rb

@@ -57,9 +57,13 @@ def test_accept_file_proc
 
   def test_file_scheme
     reader = JSON::Schema::Reader.new(:accept_uri => true, :accept_file => false)
-    assert_raises(JSON::Schema::ReadRefused) do
+    error = assert_raises(JSON::Schema::ReadRefused) do
       reader.read('file://' + ADDRESS_SCHEMA_PATH)
     end
+
+    assert_equal(:file, error.type)
+    assert_equal(ADDRESS_SCHEMA_PATH, error.location)
+    assert_equal("Read of file at #{ADDRESS_SCHEMA_PATH} refused", error.message)
   end
 
   def test_parse_error