Add serialize_persistent_params helper method (#493)

app/helpers/trestle/params_helper.rb

@@ -17,5 +17,26 @@ def persistent_params
 
       params.slice(*(flat + nested.keys)).permit(*(flat << nested))
     end
+
+    # Converts the current set of persistent params into hidden form fields, suitable
+    # for inclusion within a form tag (e.g for search or filtering).
+    #
+    # except - List of param keys to exclude
+    # only   - List of param keys to only include
+    #
+    # Returns a HTML-safe String.
+    def serialize_persistent_params(except: [], only: [])
+      params = persistent_params
+
+      if Array(only).any?
+        params = params.slice(*only)
+      elsif Array(except).any?
+        params = params.except(*except)
+      end
+
+      safe_join(to_form_params(params).map { |param|
+        tag.input(type: "hidden", name: param[:name], value: param[:value], autocomplete: "off")
+      }, "\n")
+    end
   end
 end

spec/trestle/helpers/params_helper_spec.rb

@@ -1,9 +1,9 @@
 require 'spec_helper'
 
 describe Trestle::ParamsHelper, type: :helper do
-  let(:params) { ActionController::Parameters.new(sort: :field, order: "asc", ignore: "me") }
-
   describe "#persistent_params" do
+    let(:params) { ActionController::Parameters.new(sort: :field, order: "asc", ignore: "me") }
+
     it "only returns params that should be persistent" do
       expect(persistent_params).to eq(ActionController::Parameters.new(sort: :field, order: "asc").permit!)
     end
@@ -48,4 +48,66 @@
       end
     end
   end
+
+  describe "#serialize_persistent_params" do
+    before(:each) do
+      allow(Trestle.config).to receive(:persistent_params).and_return([:sort, { array: [] }, :order, { hash: {} }])
+    end
+
+    let(:params) { ActionController::Parameters.new(sort: :field, order: "asc", ignore: "me", array: ["foo", "bar", "baz"], hash: { key1: "value1", key2: "value2" },) }
+
+    it "returns hidden input tags for each parameter" do
+      result = serialize_persistent_params
+
+      expect(result).to have_tag("input", with: { type: "hidden", name: "sort", value: "field" })
+      expect(result).to have_tag("input", with: { type: "hidden", name: "order", value: "asc" })
+      expect(result).not_to have_tag("input", with: { type: "hidden", name: "ignore", value: "me" })
+    end
+
+    it "returns a hidden input tag for each individual array parameter" do
+      result = serialize_persistent_params
+
+      expect(result).to have_tag("input", with: { type: "hidden", name: "array[]", value: "foo" })
+      expect(result).to have_tag("input", with: { type: "hidden", name: "array[]", value: "bar" })
+      expect(result).to have_tag("input", with: { type: "hidden", name: "array[]", value: "baz" })
+    end
+
+    it "returns a hidden input tag for each individual hash parameter" do
+      result = serialize_persistent_params
+
+      expect(result).to have_tag("input", with: { type: "hidden", name: "hash[key1]", value: "value1" })
+      expect(result).to have_tag("input", with: { type: "hidden", name: "hash[key2]", value: "value2" })
+    end
+
+    it "does not include specific params matching the :except option (singular)" do
+      result = serialize_persistent_params(except: :order)
+
+      expect(result).not_to have_tag("input", with: { type: "hidden", name: "order", value: "asc" })
+    end
+
+    it "does not include specific params matching the :except option (array)" do
+      result = serialize_persistent_params(except: [:order, :array])
+
+      expect(result).not_to have_tag("input", with: { type: "hidden", name: "order", value: "asc" })
+      expect(result).not_to have_tag("input", with: { type: "hidden", name: "array[]", value: "foo" })
+      expect(result).not_to have_tag("input", with: { type: "hidden", name: "array[]", value: "bar" })
+      expect(result).not_to have_tag("input", with: { type: "hidden", name: "array[]", value: "baz" })
+    end
+
+    it "only includes params matching the :only option (singular)" do
+      result = serialize_persistent_params(only: :sort)
+
+      expect(result).to have_tag("input", count: 1)
+      expect(result).to have_tag("input", with: { type: "hidden", name: "sort", value: "field" })
+    end
+
+    it "only includes params matching the :only option (array)" do
+      result = serialize_persistent_params(only: [:sort, :hash])
+
+      expect(result).to have_tag("input", count: 3)
+      expect(result).to have_tag("input", with: { type: "hidden", name: "sort", value: "field" })
+      expect(result).to have_tag("input", with: { type: "hidden", name: "hash[key1]", value: "value1" })
+      expect(result).to have_tag("input", with: { type: "hidden", name: "hash[key2]", value: "value2" })
+    end
+  end
 end