luatz/timetable.lua: Fix incorrect normalisation logic for negative day field

Fixes #13

diff --git a/NEWS b/NEWS
index d49c3427e8de2150ea36612b7d42b0222a23cf29..b4cc02dd90c80a11842e82504f434ac5d0f93c2c 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,6 @@
 UNRELEASED
 
-  - Fix timetable normalisation carry bug (#10)
+  - Fix timetable normalisation carry bugs (#10, #13)
   - Clean up of docs
   - No longer throw errors in parse module on error (now return nil, err)
   - Support version 3 tzfiles

diff --git a/luatz/timetable.lua b/luatz/timetable.lua
index 0dbf4c8eedb5d6fdce95d0f80187ef08e1363de0..6bae913470bbd151ea4f2384210b448391f2547e 100644 (file)
--- a/luatz/timetable.lua
+++ b/luatz/timetable.lua
@@ -107,8 +107,12 @@ local function normalise ( year , month , day , hour , min , sec )
        -- Add a whole year of days at a time, this is later resolved by adding months
        -- TODO[OPTIMIZE]: This could be slow if `day` is far out of range
        while day < 0 do
-               year = year - 1
-               day  = day + year_length ( year )
+               month = month - 1
+               if month < 0 then
+                       year = year - 1
+                       month = 11
+               end
+               day = day + month_length ( month + 1 , year )
        end
        year , month = carry ( year , month , 12 )
 

diff --git a/spec/timetable_spec.lua b/spec/timetable_spec.lua
index 930d36b32b94f398f260580352ee980a6e4497d8..6c9617e2c2dcce2a1e59dc94a0f0407c6534568b 100644 (file)
--- a/spec/timetable_spec.lua
+++ b/spec/timetable_spec.lua
@@ -77,8 +77,8 @@ describe ( "Timetable library" , function ( )
                assert.same({ 2012,3,23,0,0,0 }, { timetable.normalise(2012,2,52,0,0,0) })
                assert.same({ 2013,3,24,0,0,0 }, { timetable.normalise(2013,2,52,0,0,0) })
 
-               assert.same({ 2012,2,26,0,0,0 }, { timetable.normalise(2012,3,-2,0,0,0) })
-               assert.same({ 2013,2,27,0,0,0 }, { timetable.normalise(2013,3,-2,0,0,0) })
+               assert.same({ 2012,2,27,0,0,0 }, { timetable.normalise(2012,3,-2,0,0,0) })
+               assert.same({ 2013,2,26,0,0,0 }, { timetable.normalise(2013,3,-2,0,0,0) })
 
                -- Also when more fields are out of range
                assert.same({ 2016,7,22,0,0,0 }, { timetable.normalise(2013,42,52,0,0,0) })
@@ -98,6 +98,12 @@ describe ( "Timetable library" , function ( )
                assert.same({ 2017,02,3,0,0,0 }, { timetable.normalise(2017,02,13,0,-14400,0) })
        end )
 
+       it ( "#normalise handles negative day carry (issue #13)", function()
+               assert.same({ 2016,11,30,00,00,00 }, { timetable.normalise(2016,12,0,0,0,0) })
+               assert.same({ 2017,11,30,00,00,00 }, { timetable.normalise(2017,12,0,0,0,0) })
+               assert.same({ 2018,11,30,00,00,00 }, { timetable.normalise(2018,12,0,0,0,0) })
+       end )
+
        local function round_trip_add(t, field, x)
                local before = t:clone()
                t[field]=t[field]+x;