When an Id can't be resolved, render a 404, per the IIIF spec

app/resolvers/riiif/abstract_file_system_resolver.rb

@@ -25,7 +25,7 @@ def find(id)
     # @return the path of the file
     def path(id)
       search = pattern(id)
-      Dir.glob(search).first || raise(ImageNotFoundError, search)
+      search && Dir.glob(search).first || raise(ImageNotFoundError, search)
     end
 
     def pattern(_id)

app/resolvers/riiif/file_system_file_resolver.rb

@@ -2,8 +2,12 @@ module Riiif
   class FileSystemFileResolver < AbstractFileSystemResolver
     attr_writer :input_types
 
+    # @return nil when the id is not valid
     def pattern(id)
-      raise ArgumentError, "Invalid characters in id `#{id}`" unless id =~ /^[\w\-:]+$/
+      unless id =~ /^[\w\-:]+$/
+        Rails.logger.warn "Invalid characters in id `#{id}`"
+        return
+      end
       ::File.join(base_path, "#{id}.{#{input_types.join(',')}}")
     end
 

spec/models/riiif/file_system_file_resolver_spec.rb

@@ -21,6 +21,14 @@
         expect(subject.path).to eq base_path + '/world.jp2'
       end
     end
+
+    context 'when pattern raises an ArgumentError' do
+      let(:id) { 'foo/bar' } # slashes are not permitted by default
+
+      it 'casts the error to a not found (required by the IIIF spec)' do
+        expect { subject.path }.to raise_error Riiif::ImageNotFoundError
+      end
+    end
   end
 
   describe '#input_types' do
@@ -63,5 +71,12 @@
         expect { subject }.not_to raise_error
       end
     end
+
+    context 'with slashes (unallowed by default)' do
+      let(:id) { 'fo/baz' }
+      it 'returns nil' do
+        expect(subject).to be_nil
+      end
+    end
   end
 end