Support 2-arity options for Calendar.strftime/3

lib/elixir/lib/calendar.ex

@@ -461,25 +461,30 @@ defmodule Calendar do
       it can't contain the `%X` format and defaults to `"%H:%M:%S"`
       if the option is not received
 
-    * `:am_pm_names` - a function that receives either `:am` or `:pm` and returns
+    * `:am_pm_names` - a function that receives either `:am` or `:pm`
+      (and also the datetime if the function is arity/2) and returns
       the name of the period of the day, if the option is not received it defaults
       to a function that returns `"am"` and `"pm"`, respectively
 
-    *  `:month_names` - a function that receives a number and returns the name of
+    *  `:month_names` - a function that receives a number (and also the
+      datetime if the function is arity/2) and returns the name of
       the corresponding month, if the option is not received it defaults to a
       function that returns the month names in English
 
-    * `:abbreviated_month_names` - a function that receives a number and returns the
+    * `:abbreviated_month_names` - a function that receives a number (and also
+      the datetime if the function is arity/2) and returns the
       abbreviated name of the corresponding month, if the option is not received it
       defaults to a function that returns the abbreviated month names in English
 
-    * `:day_of_week_names` - a function that receives a number and returns the name of
+    * `:day_of_week_names` - a function that receives a number and (and also the
+      datetime if the function is arity/2) returns the name of
       the corresponding day of week, if the option is not received it defaults to a
       function that returns the day of week names in English
 
-    * `:abbreviated_day_of_week_names` - a function that receives a number and returns
-      the abbreviated name of the corresponding day of week, if the option is not received
-      it defaults to a function that returns the abbreviated day of week names in English
+    * `:abbreviated_day_of_week_names` - a function that receives a number (and also
+      the datetime if the function is arity/2) and returns the abbreviated name of
+      the corresponding day of week, if the option is not received it defaults to a
+      function that returns the abbreviated day of week names in English
 
   ## Formatting syntax
 
@@ -650,12 +655,12 @@ defmodule Calendar do
     format_modifiers(rest, width, pad, datetime, format_options, acc)
   end
 
-  defp am_pm(hour, format_options) when hour > 11 do
-    format_options.am_pm_names.(:pm)
+  defp am_pm(hour, format_options, datetime) when hour > 11 do
+    apply_format(:pm, format_options.am_pm_names, datetime)
   end
 
-  defp am_pm(hour, format_options) when hour <= 11 do
-    format_options.am_pm_names.(:am)
+  defp am_pm(hour, format_options, datetime) when hour <= 11 do
+    apply_format(:am, format_options.am_pm_names, datetime)
   end
 
   defp default_pad(format) when format in ~c"aAbBpPZ", do: ?\s
@@ -676,7 +681,7 @@ defmodule Calendar do
     result =
       datetime
       |> Date.day_of_week()
-      |> format_options.abbreviated_day_of_week_names.()
+      |> apply_format(format_options.abbreviated_day_of_week_names, datetime)
       |> pad_leading(width, pad)
 
     parse(rest, datetime, format_options, [result | acc])
@@ -687,7 +692,7 @@ defmodule Calendar do
     result =
       datetime
       |> Date.day_of_week()
-      |> format_options.day_of_week_names.()
+      |> apply_format(format_options.day_of_week_names, datetime)
       |> pad_leading(width, pad)
 
     parse(rest, datetime, format_options, [result | acc])
@@ -697,15 +702,18 @@ defmodule Calendar do
   defp format_modifiers("b" <> rest, width, pad, datetime, format_options, acc) do
     result =
       datetime.month
-      |> format_options.abbreviated_month_names.()
+      |> apply_format(format_options.abbreviated_month_names, datetime)
       |> pad_leading(width, pad)
 
     parse(rest, datetime, format_options, [result | acc])
   end
 
   # Full month name
   defp format_modifiers("B" <> rest, width, pad, datetime, format_options, acc) do
-    result = datetime.month |> format_options.month_names.() |> pad_leading(width, pad)
+    result =
+      datetime.month
+      |> apply_format(format_options.month_names, datetime)
+      |> pad_leading(width, pad)
 
     parse(rest, datetime, format_options, [result | acc])
   end
@@ -783,7 +791,11 @@ defmodule Calendar do
 
   # "AM" or "PM" (noon is "PM", midnight as "AM")
   defp format_modifiers("p" <> rest, width, pad, datetime, format_options, acc) do
-    result = datetime.hour |> am_pm(format_options) |> String.upcase() |> pad_leading(width, pad)
+    result =
+      datetime.hour
+      |> am_pm(format_options, datetime)
+      |> String.upcase()
+      |> pad_leading(width, pad)
 
     parse(rest, datetime, format_options, [result | acc])
   end
@@ -792,7 +804,7 @@ defmodule Calendar do
   defp format_modifiers("P" <> rest, width, pad, datetime, format_options, acc) do
     result =
       datetime.hour
-      |> am_pm(format_options)
+      |> am_pm(format_options, datetime)
       |> String.downcase()
       |> pad_leading(width, pad)
 
@@ -958,6 +970,19 @@ defmodule Calendar do
   defp do_pad_leading(count, padding, acc),
     do: do_pad_leading(count - 1, padding, [padding | acc])
 
+  defp apply_format(term, formatter, datetime) do
+    case Function.info(formatter, :arity) do
+      {:arity, 1} ->
+        formatter.(term)
+
+      {:arity, 2} ->
+        formatter.(term, datetime)
+
+      {:arity, n} ->
+        raise ArgumentError, "Formatter funtion must be of arity 1 or 2. Found #{inspect(n)}"
+    end
+  end
+
   defp options(user_options) do
     default_options = %{
       preferred_date: "%Y-%m-%d",

lib/elixir/test/elixir/calendar_test.exs

@@ -397,6 +397,39 @@ defmodule CalendarTest do
              ) == "четверг ЧТВ P Agosto Ago % 02019-08-15 07: 1757"
     end
 
+    test "formats according to custom configs with 2-arity functions" do
+      assert Calendar.strftime(
+               ~U[2019-08-15 17:07:57.001Z],
+               "%A %a %p %B %b %c %x %X",
+               am_pm_names: fn
+                 :am, ~U[2019-08-15 17:07:57.001Z] -> "a"
+                 :pm, ~U[2019-08-15 17:07:57.001Z] -> "p"
+               end,
+               month_names: fn month, ~U[2019-08-15 17:07:57.001Z] ->
+                 {"Janeiro", "Fevereiro", "Março", "Abril", "Maio", "Junho", "Julho", "Agosto",
+                  "Setembro", "Outubro", "Novembro", "Dezembro"}
+                 |> elem(month - 1)
+               end,
+               day_of_week_names: fn day_of_week, ~U[2019-08-15 17:07:57.001Z] ->
+                 {"понедельник", "вторник", "среда", "четверг", "пятница", "суббота",
+                  "воскресенье"}
+                 |> elem(day_of_week - 1)
+               end,
+               abbreviated_month_names: fn month, ~U[2019-08-15 17:07:57.001Z] ->
+                 {"Jan", "Fev", "Mar", "Abr", "Mai", "Jun", "Jul", "Ago", "Set", "Out", "Nov",
+                  "Dez"}
+                 |> elem(month - 1)
+               end,
+               abbreviated_day_of_week_names: fn day_of_week, ~U[2019-08-15 17:07:57.001Z] ->
+                 {"ПНД", "ВТР", "СРД", "ЧТВ", "ПТН", "СБТ", "ВСК"}
+                 |> elem(day_of_week - 1)
+               end,
+               preferred_date: "%05Y-%m-%d",
+               preferred_time: "%M:%_3H%S",
+               preferred_datetime: "%%"
+             ) == "четверг ЧТВ P Agosto Ago % 02019-08-15 07: 1757"
+    end
+
     test "raises on unknown option according to custom configs" do
       assert_raise ArgumentError, "unknown option :unknown given to Calendar.strftime/3", fn ->
         Calendar.strftime(~D[2019-08-15], "%D", unknown: "option")