Allow plural forms to be set for gettext as a whole

Closes #264.
Closes #179.

lib/gettext/compiler.ex

@@ -375,7 +375,9 @@ defmodule Gettext.Compiler do
   # Compiles all the `.po` files in the given directory (`dir`) into `lgettext/4`
   # and `lngettext/6` function clauses.
   defp compile_po_files(env, known_po_files, opts) do
-    plural_mod = Keyword.get(opts, :plural_forms, Gettext.Plural)
+    plural_mod =
+      Keyword.get(opts, :plural_forms) ||
+        Application.get_env(:gettext, :plural_forms, Gettext.Plural)
 
     if Keyword.get(opts, :one_module_per_locale, false) do
       known_po_files

lib/gettext/merger.ex

@@ -219,7 +219,8 @@ defmodule Gettext.Merger do
 
   defp put_plural_forms_opt(opts, headers, locale) do
     Keyword.put_new_lazy(opts, :plural_forms, fn ->
-      read_plural_forms_from_headers(headers) || Gettext.Plural.nplurals(locale)
+      read_plural_forms_from_headers(headers) ||
+        Application.get_env(:gettext, :plural_forms, Gettext.Plural).nplurals(locale)
     end)
   end
 

lib/gettext/plural.ex

@@ -52,16 +52,33 @@ defmodule Gettext.Plural do
         def plural(locale, n), do: Gettext.Plural.plural(locale, n)
       end
 
-      defmodule MyApp.Gettext do
-        use Gettext, otp_app: :my_app, plural_forms: MyApp.Plural
-      end
-
   The mathematical expressions used in this module to determine the plural form
   of a given number of elements are taken from [this
   page](http://localization-guide.readthedocs.org/en/latest/l10n/pluralforms.html#f2)
   as well as from [Mozilla's guide on "Localization and
   plurals"](https://developer.mozilla.org/en-US/docs/Mozilla/Localization/Localization_and_Plurals).
 
+  Now that we have defined our custom plural forms, we can use them
+  in two ways. You can set it for all `:gettext` backends in your
+  config files:
+
+      config :gettext, :plural_forms, MyApp.Plural
+
+  Or to each specific backend:
+
+      defmodule MyApp.Gettext do
+        use Gettext, otp_app: :my_app, plural_forms: MyApp.Plural
+      end
+
+  Notice that tasks such as `mix gettext.merge` use the plural
+  backend configured under the `:gettext` application, so generally
+  speaking the first format is preferred.
+
+  Note some tasks also allow the number of plural forms to be given
+  explicitly, for example:
+
+      mix gettext.merge priv/gettext --locale=gsw_CH --plural-forms=2
+
   ### Unknown locales
 
   Trying to call `Gettext.Plural` functions with unknown locales will result in

mix.exs

@@ -31,7 +31,7 @@ defmodule Gettext.Mixfile do
   def application do
     [
       extra_applications: [:logger],
-      env: [default_locale: "en"],
+      env: [default_locale: "en", plural_forms: Gettext.Plural],
       mod: {Gettext.Application, []}
     ]
   end

test/gettext_test.exs

@@ -11,16 +11,7 @@ defmodule GettextTest.TranslatorWithAllowedLocales do
 end
 
 defmodule GettextTest.TranslatorWithCustomPluralForms do
-  defmodule Plural do
-    @behaviour Gettext.Plural
-    def nplurals("elv"), do: 2
-    def nplurals(other), do: Gettext.Plural.nplurals(other)
-    # Opposite of Italian (where 1 is singular, everything else is plural)
-    def plural("it", 1), do: 1
-    def plural("it", _), do: 0
-  end
-
-  use Gettext, otp_app: :test_application, plural_forms: Plural
+  use Gettext, otp_app: :test_application, plural_forms: GettextTest.CustomPlural
 end
 
 defmodule GettextTest.TranslatorWithDefaultDomain do
@@ -177,6 +168,24 @@ defmodule GettextTest do
              {:ok, "Una nuova email"}
   end
 
+  test "using a custom Gettext.Plural module from app environment" do
+    Application.put_env(:gettext, :plural_forms, GettextTest.CustomPlural)
+
+    defmodule TranslatorWithAppPluralForms do
+      use Gettext, otp_app: :test_application
+    end
+
+    alias TranslatorWithAppPluralForms, as: T
+
+    assert T.lngettext("it", "default", nil, "One new email", "%{count} new emails", 1, %{}) ==
+             {:ok, "1 nuove email"}
+
+    assert T.lngettext("it", "default", nil, "One new email", "%{count} new emails", 2, %{}) ==
+             {:ok, "Una nuova email"}
+  after
+    Application.put_env(:gettext, :plural_forms, Gettext.Plural)
+  end
+
   test "translations can be pluralized" do
     import Translator, only: [lngettext: 7]
 

test/mix/tasks/gettext.merge_test.exs

@@ -110,6 +110,61 @@ defmodule Mix.Tasks.Gettext.MergeTest do
     assert String.starts_with?(new_po, "## \"msgid\"s in this file come from POT")
   end
 
+  test "passing a dir and a --locale opt will update/create PO files in the locale dir with custom plural forms" do
+    write_file("new.pot", """
+    msgid "new"
+    msgstr ""
+    """)
+
+    output =
+      capture_io(fn ->
+        run([@priv_path, "--locale", "it", "--plural-forms", "3"])
+      end)
+
+    assert output =~ "Wrote tmp/gettext.merge/it/LC_MESSAGES/new.po"
+    new_po = read_file("it/LC_MESSAGES/new.po")
+
+    assert new_po =~ ~S"""
+           msgid ""
+           msgstr ""
+           "Language: it\n"
+           "Plural-Forms: nplurals=3\n"
+
+           msgid "new"
+           msgstr ""
+           """
+  end
+
+
+  test "passing a dir and a --locale opt will update/create PO files in the locale dir with app env plural forms" do
+    Application.put_env(:gettext, :plural_forms, GettextTest.CustomPlural)
+
+    write_file("new.pot", """
+    msgid "new"
+    msgstr ""
+    """)
+
+    output =
+      capture_io(fn ->
+        run([@priv_path, "--locale", "elv"])
+      end)
+
+    assert output =~ "Wrote tmp/gettext.merge/elv/LC_MESSAGES/new.po"
+    new_po = read_file("elv/LC_MESSAGES/new.po")
+
+    assert new_po =~ ~S"""
+           msgid ""
+           msgstr ""
+           "Language: elv\n"
+           "Plural-Forms: nplurals=2\n"
+
+           msgid "new"
+           msgstr ""
+           """
+  after
+    Application.put_env(:gettext, :plural_forms, Gettext.Plural)
+  end
+
   test "passing just a dir merges with PO files in every locale" do
     write_file("fr/LC_MESSAGES/foo.po", "")
     write_file("it/LC_MESSAGES/foo.po", "")

test/test_helper.exs

@@ -3,4 +3,13 @@
 |> Path.join()
 |> Code.prepend_path()
 
+defmodule GettextTest.CustomPlural do
+  @behaviour Gettext.Plural
+  def nplurals("elv"), do: 2
+  def nplurals(other), do: Gettext.Plural.nplurals(other)
+  # Opposite of Italian (where 1 is singular, everything else is plural)
+  def plural("it", 1), do: 1
+  def plural("it", _), do: 0
+end
+
 ExUnit.start()