Merge pull request #342 from lambdalisue/fix/datetime_improve_response

DateTime: Fix 'strftime()' to follow timezone of the DateTime object

autoload/vital/__latest__/DateTime.vim

@@ -46,6 +46,7 @@ function! s:_vital_loaded(V) abort
   \   '_days': 0,
   \   '_seconds': 0,
   \ })
+  let s:tz_default_offset = s:timezone().offset()
 endfunction
 
 function! s:_vital_depends() abort
@@ -454,8 +455,18 @@ function! s:DateTime.format(format, ...) abort
 endfunction
 " @vimlint(EVL102, 0, l:locale)
 function! s:DateTime.strftime(format, ...) abort
-  let expr = printf('strftime(%s, %d)', string(a:format), self.unix_time())
-  return s:_with_locale(expr, a:0 ? a:1 : '')
+  let tz = self.timezone()
+  let ts = self.unix_time() + tz.offset() - s:tz_default_offset
+  let locale = get(a:000, 0, '')
+  let format = a:format =~? '%z'
+        \ ? substitute(a:format, '%z', tz.offset_string(), 'g')
+        \ : a:format
+  if empty(locale)
+    return strftime(format, ts)
+  else
+    let expr = printf('strftime(%s, %d)', string(format), ts)
+    return s:_with_locale(expr, locale)
+  endif
 endfunction
 function! s:DateTime.to_string() abort
   return self.format('%c')

doc/vital-date_time.txt

@@ -192,9 +192,19 @@ DateTime.format({format} [, {locale}])
 	See |Vital.DateTime-format| about {format}.
 
 				*Vital.DateTime-DateTime.strftime()*
-DateTime.strftime({format} [, {locate}])
-	Same as "strftime({format}, dt.unix_time())".
-	Note that timezone is always converted to current timezone.
+DateTime.strftime({format} [, {locale}])
+	An alternative version of |Vital.DateTime-DateTime.format()| which
+	use |strftime()| internally. While |Vital.DateTime-DateTime.format()|
+	parse {format}, it is really slow compared to using |strftime()|.
+	However |Vital.DateTime-DateTime.format()| is required while accepted
+	{format} and a return value of |strftime()| depends on the system.
+	That's why this function exists for user who need performance but the
+	accuracy.
+	It substitutes '%z' in {format} into the value returned from
+	|Vital.DateTime-TimeZone.offset_string()| while |strftime()| always
+	return the system default timezone offset string.
+	See https://gist.github.com/lambdalisue/e73bd722ca8840e82bd8
+	for benchmarking.
 
 DateTime.to_string()		*Vital.DateTime-DateTime.to_string()*
 	Same as "format('%c')".

test/DateTime.vimspec

@@ -671,8 +671,19 @@ Describe DateTime
     End
 
     Describe .strftime()
-      It is same as "strftime({format}, dt.unix_time())"
-        Assert Equals(dt.strftime('%c'), strftime('%c', dt.unix_time()))
+      Before
+        " Use non default timezone
+        let tz = DT.timezone().offset_string() ==# '+0300' ? '+0500' : '+0300'
+        let dt = DT.from_date(2012, 1, 2, 3, 4, 5, tz)
+      End
+
+      It is same as "format('%z')"
+        Assert Equals(dt.strftime('%z'), dt.format('%z'))
+      End
+
+      It is same as "format('%Y-%m-%d %H:%M:%S')"
+        let ft = '%Y-%m-%d %H:%M:%S'
+        Assert Equals(dt.strftime(ft), dt.format(ft))
       End
     End