fix: preserve data immutability and improve count interpolation

- Create new data table for default count value
- Move count default handling to treatNode
- Update tests to verify count interpolation
- Maintain immutability of input data table

Cherry-picked from kikito/i18n.lua#35

i18n/init.lua

@@ -97,7 +97,7 @@ local function pluralize(t, locale, data)
   return t[plural_form]
 end
 
-local function treatNode(node, data)
+local function treatNode(node, loc, data)
   if isArray(node) then
     local iter = {ipairs(node)}
     node = {}
@@ -107,7 +107,18 @@ local function treatNode(node, data)
   elseif type(node) == 'string' then
     return interpolate(node, data)
   elseif isPluralTable(node) then
-    return interpolate(pluralize(node, loc, data), data)
+    -- Make sure that count has a default of 1
+    local newdata
+    if data.count == nil then
+        newdata = {}
+        for key, value in pairs(data) do
+            newdata[key] = value
+        end
+        newdata.count = 1
+    else
+        newdata = data
+    end
+    return interpolate(pluralize(node, loc, newdata), newdata)
   end
   return node
 end

spec/i18n_spec.lua

@@ -95,20 +95,21 @@ describe('i18n', function()
         before_each(function()
           i18n.setLocale('fr')
           i18n.set('fr.message', {
-            one   = "Une chose.",
+            one   = "%{count} chose.",
             other = "%{count} choses."
           })
         end)
 
         it('Ça marche', function()
-          assert.equal("Une chose.", i18n('message', {count = 1}))
-          assert.equal("Une chose.", i18n('message', {count = 1.5}))
+          assert.equal("1 chose.", i18n('message', {count = 1}))
+          -- Note: should actually be '1,5 chose.'
+          assert.equal("1.5 chose.", i18n('message', {count = 1.5}))
           assert.equal("2 choses.", i18n('message', {count = 2}))
-          assert.equal("Une chose.", i18n('message', {count = 0}))
+          assert.equal("0 chose.", i18n('message', {count = 0}))
         end)
 
         it('defaults to 1', function()
-          assert.equal("Une chose.", i18n('message'))
+          assert.equal("1 chose.", i18n('message'))
         end)
       end)