fix: take DST into account in augend.date["%H:%M"]

When trying to increase/decrease a time from a Europe/Paris time zone,
dial cannot find the time pattern because `os.date` will take DST into
account and will return a time increased by 1 hour.

By preserving DST value from the host, consistency is ensured between
the calls to `os.date`.

Run the date_spec.lua file with different time zones in order to
correctly test DST during the whole year.

Link: https://en.wikipedia.org/wiki/Daylight_saving_time_by_country
Signed-off-by: Thomas Faivre <[email protected]>

lua/dial/augend/date.lua

@@ -461,6 +461,7 @@ function DateFormat:find(line, cursor)
         local now = os.date("*t", os.time()) --[[@as osdate]]
         dt_info.month = now.month
         dt_info.year = now.year
+        dt_info.isdst = now.isdst
     end
 
     local datekind = self.default_kind

run

@@ -1,16 +1,56 @@
 #!/usr/bin/env bash
 
 TESTS_INIT=tests/minimal_init.lua
-TESTS_DIR=tests/
+TESTS_DIR=tests
 
+function _test_tz {
+	# DST always in effect
+	echo "Checking with $1 time zone (DST always enable)"
+	TZ=$1
+	export TZ
+	nvim \
+		--headless \
+		--noplugin \
+		-u ${TESTS_INIT} \
+		-c "PlenaryBustedDirectory ${TESTS_DIR}/dial/augend/date_spec.lua \
+	    { minimal_init = '${TESTS_INIT}' }"
+}
 
 function test {
 
+	# Force TimeZone to ensure consistent behavior of os.date regarding Daylight
+	# Saving Time
+
+	# Standard case (No DST)
+	# Full test case
+	TZ='GMT+0'
+	export TZ
 	nvim \
 		--headless \
 		--noplugin \
 		-u ${TESTS_INIT} \
-		-c "PlenaryBustedDirectory ${TESTS_DIR} { minimal_init = '${TESTS_INIT}' }"
+		-c "PlenaryBustedDirectory ${TESTS_DIR} \
+	   { minimal_init = '${TESTS_INIT}' }" ||
+		return 1
+
+	# permanent DST: os.date always returns `isdst == false`
+	_test_tz "Asia/Tokyo" || return 1
+
+	# Check standard DST. Since the date is not controlled, we might have
+	# periods of time without any timezone with `isdst == true`.
+	# Therefore, select timezones that overlap so that DST is actually
+	# tested.
+
+	# DST in Northern hemisphere
+	# Start: Second Sunday in March at 2:00
+	# End: First Sunday in November at 2:00
+	_test_tz "America/New_York" || return 1
+
+	# DST in Southern hemisphere
+	# Start: First Sunday in October at 2:00
+	# End: First Sunday in April at 3:00
+	_test_tz "Australia/Sidney" || return 1
+
 }
 
 

tests/dial/augend/date_spec.lua

@@ -158,6 +158,22 @@ describe([[Test of date with format "%Y年%-m月%-d日(%ja)":]], function()
     end)
 end)
 
+describe([[Test of date with format %H:%M:]], function()
+    local augend = date.alias["%H:%M"]
+    describe("find function", function()
+        it("can find dates in a given format with Time Zones", function()
+            assert.are.same(augend:find_stateful("date: 11:50", 1), { from = 7, to = 11 })
+            assert.are.same(augend.kind, "min")
+            assert.are.same(augend:find_stateful("date: 11:50", 6), { from = 7, to = 11 })
+            assert.are.same(augend.kind, "min")
+            assert.are.same(augend:find_stateful("date: 11:50", 7), { from = 7, to = 11 })
+            assert.are.same(augend.kind, "hour")
+            assert.are.same(augend:find_stateful("date: 11:50", 10), { from = 7, to = 11 })
+            assert.are.same(augend.kind, "min")
+        end)
+    end)
+end)
+
 describe([[Test of clamp & end_sensitive option:]], function()
     describe("{clamp = false and end_sensitive = false}", function()
         local augend = date.new {