SearchBuilder#except

Just like #append, but removes processor chain methods instead of
appending them.

lib/blacklight/search_builder.rb

@@ -56,6 +56,27 @@ def append *addl_processor_chain
       builder
     end
 
+    ##
+    # Converse to append, remove processor chain directives,
+    # returning a new builder that's a copy of receiver with
+    # specified change. 
+    #
+    # Methods in argument that aren't currently in processor
+    # chain are ignored as no-ops, rather than raising. 
+    def except *except_processor_chain
+      builder = self.class.new(processor_chain - except_processor_chain, scope)
+          .with(blacklight_params)
+          .merge(@merged_params)
+          .reverse_merge(@reverse_merged_params)
+
+      builder.start(@start) if @start
+      builder.rows(@rows) if @rows
+      builder.page(@page) if @page
+      builder.facet(@facet) if @facet
+
+      builder
+    end
+
     ##
     # Merge additional, repository-specific parameters
     def merge extra_params, &block

spec/lib/blacklight/search_builder_spec.rb

@@ -47,6 +47,17 @@
     end
   end
 
+  describe "#except" do
+    let(:processor_chain) { [:a, :b, :c, :d, :e] }
+    it "should provide a new search builder excepting arguments" do
+      builder = subject.except(:b, :d, :does_not_exist)
+      expect(builder).not_to equal(subject)
+      expect(subject.processor_chain).to eq processor_chain
+      expect(builder.processor_chain).not_to eq subject.processor_chain
+      expect(builder.processor_chain).to match_array [:a, :c, :e]
+    end
+  end
+
   describe "#to_hash" do
     it "should append the extra parameters to the result" do
       Deprecation.silence(Blacklight::SearchBuilder) do