Add BYSETPOS Validation

CHANGELOG.md

@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- some validation for ensuring BYSETPOS rule is used in conjunction with another BY* part rule. ([ignitionapp/ice_cube #5](https://github.com/ignitionapp/ice_cube/pull/5))
+
 ### Added
 - Indonesian translations. ([#505](https://github.com/seejohnrun/ice_cube/pull/505)) by [@achmiral](https://github.com/achmiral)
 - Support for BYSETPOS, including tests, and fixes for minor bugs (ie. Rule.from_hash, and Rule.to_s)

lib/ice_cube/flexible_hash.rb

@@ -25,9 +25,9 @@ def delete(key)
 
     def _match_key(key)
       return key if __getobj__.has_key? key
-      if Symbol == key.class
+      if key.instance_of?(Symbol)
         __getobj__.keys.detect { |k| return k if k == key.to_s }
-      elsif String == key.class
+      elsif key.instance_of(String)
         __getobj__.keys.detect { |k| return k if k.to_s == key }
       end
       key

lib/ice_cube/rule.rb

@@ -84,13 +84,39 @@ def from_hash(original_hash)
           apply_validation(rule, name, args)
         end
 
+        unless hash[:validations][:by_set_pos].nil?
+          unless validate_by_set_pos_by_parts(rule, hash[:validations])
+            raise ArgumentError, "BYSETPOS must be used in conjuction with another BY* rule part"
+          end
+        end
+
         unless hash[:by_set_pos].nil?
           rule.send(:by_set_pos, hash[:by_set_pos])
         end
 
         rule
       end
 
+      def validate_by_set_pos_by_parts(rule, validations)
+        by_parts = [
+          :month_of_year,
+          :week_of_year,
+          :day_of_year,
+          :day_of_month,
+          :day,
+          :day_of_week,
+          :hour_of_day,
+          :minute_of_hour,
+          :second_of_minute
+        ]
+
+        if !!validations[:by_set_pos]
+          by_parts.any? { |part| validations[part] }
+        else
+          true
+        end
+      end
+
       private
 
       def apply_validation(rule, name, args)

spec/examples/from_ical_spec.rb

@@ -410,6 +410,11 @@ def sorted_ical(ical)
         str = "FREQ=DAILY;FAKE=23"
         expect { Rule.from_ical(str) }.to raise_error(ArgumentError, "Invalid rule validation type: FAKE")
       end
+
+      it "should raise ArgumentError when parsing BYSETPOS without another BY* part rule" do
+        str = "FREQ=MONTHLY;BYSETPOS=-1"
+        expect { Rule.from_ical(str) }.to raise_error(ArgumentError, "BYSETPOS must be used in conjuction with another BY* rule part")
+      end
     end
 
     describe "multiple rules" do
@@ -443,6 +448,11 @@ def sorted_ical(ical)
         it_behaves_like "an invalid ical string"
       end
 
+      describe "BYSETPOS without another BY* part rule" do
+        let(:ical_str) { "RRULE:FREQ=MONTHLY;BYSETPOS=-1" }
+        it_behaves_like "an invalid ical string"
+      end
+
       describe "invalid rule with invalid sensitive key" do
         let(:ical_str) { "RRULE:FREQ=WEKLY;WKST=SU" }
         it_behaves_like "an invalid ical string"