Support L in dom field

Author: ojab

lib/cron_parser.rb

@@ -136,14 +136,18 @@ def last(now = @time_source.now, num=1)
   end
 
 
-  SUBELEMENT_REGEX = %r{^(\d+)(-(\d+)(/(\d+))?)?$}
-  def parse_element(elem, allowed_range)
+  SUBELEMENT_REGEX = %r{^(\d+|l)(-(\d+)(/(\d+))?)?$}
+  def parse_element(elem, allowed_range, field_name = nil)
     values = elem.split(',').map do |subel|
       if subel =~ /^\*/
         step = subel.length > 1 ? subel[2..-1].to_i : 1
         stepped_range(allowed_range, step)
       else
         if SUBELEMENT_REGEX === subel
+          if field_name != :dom && $1.include?('l')
+            raise ArgumentError, "'L' specification is supported only for DOM field"
+          end
+
           if $5 # with range
             stepped_range($1.to_i..$3.to_i, $5.to_i)
           elsif $3 # range without step
@@ -186,6 +190,7 @@ def interpolate_weekdays_without_cache(year, month)
     # then we only need to match *one* for cron to run the job:
     if not (mday_field == '*' and wday_field == '*')
       valid_mday = [] if mday_field == '*'
+      valid_mday = [(t.next_month - 1).day] if mday_field == 'l'
       valid_wday = [] if wday_field == '*'
     end
     # Careful: crontabs may use either 0 or 7 for Sunday:
@@ -251,7 +256,7 @@ def time_specs
       {
         :minute => parse_element(tokens[0], 0..59), #minute
         :hour   => parse_element(tokens[1], 0..23), #hour
-        :dom    => parse_element(tokens[2], 1..31), #DOM
+        :dom    => parse_element(tokens[2], 1..31, :dom), #DOM
         :month  => parse_element(tokens[3], 1..12), #mon
         :dow    => parse_element(tokens[4], 0..6)  #DOW
       }

spec/cron_parser_spec.rb

@@ -77,6 +77,8 @@ def parse_date(str)
     ["15-59/15 * * * *",      "2014-02-01 15:45",  "2014-02-01 16:15",4],
     ["15-59/15 * * * *",      "2014-02-01 15:46",  "2014-02-01 16:15",3],
     ["15-59/15 * * * *",      "2014-02-01 15:46",  "2014-02-01 16:15",2],
+    ["* * L 2 *",             "2015-02-01 15:36",  "2015-02-28 00:00",1],
+    ["* * L 2 *",             "2016-02-01 15:36",  "2016-02-29 00:00",1]
   ].each do |line, now, expected_next,num|
     it "returns #{expected_next} for '#{line}' when now is #{now}" do
       parsed_now = parse_date(now)
@@ -156,6 +158,8 @@ def parse_date(str)
     ["15-59/15 * * * *",      "2014-02-01 15:36",  "2014-02-01 15:30"],
     ["15-59/15 * * * *",      "2014-02-01 15:45",  "2014-02-01 15:30"],
     ["15-59/15 * * * *",      "2014-02-01 15:46",  "2014-02-01 15:45"],
+    ["* * L 2 *",             "2014-02-01 15:36",  "2013-02-28 23:59"],
+    ["* * L 2 *",             "2017-02-01 15:36",  "2016-02-29 23:59"]
   ].each do |line, now, expected_next|
     it "should return #{expected_next} for '#{line}' when now is #{now}" do
       now = parse_date(now)
@@ -176,6 +180,19 @@ def parse_date(str)
   it 'should raise error when given an invalid cronline' do
     expect { CronParser.new('* * * *') }.to raise_error('not a valid cronline')
   end
+
+  it 'should not raise error when L is passed in DOM field' do
+    expect { CronParser.new('* * L * *').next }.not_to raise_error
+  end
+
+  (0..4).each do |n|
+    next if n == 2
+    it "should raise error when L is passed in #{n} field" do
+      spec = Array.new(5) { '*' }
+      spec[n] = 'L'
+      expect { CronParser.new(spec.join(' ')).next }.to raise_error("'L' specification is supported only for DOM field")
+    end
+  end
 end
 
 RSpec.describe "time source" do