Warn when stringsdict→pot drops plural forms other than one/other

The forward conversion only maps `one`/`other` onto gettext
`msgid`/`msgid_plural`. Any other CLDR category in the English source —
most commonly a `zero` literal override, which iOS honors even for
English (Apple's docs return "No homes found" for 0) — has no gettext
slot and was dropped from the `.pot` silently, so it never reached the
translation system and vanished from every localized build.

gettext/GlotPress can't carry a literal-0 override as a plural form (a
2-form locale has nowhere to put it), so the right home for such
count-specific messages is a dedicated string selected in code
(`if count == 0`), not a `zero` key in a `.stringsdict` bound for this
pipeline. Rather than carry it through, surface it: `build_pot_entry`
now logs a `UI.important` warning naming the entry, variable, and
dropped categories, and the action docs state the limitation. The
converted output is unchanged.

Author: jkmassel

CHANGELOG.md

@@ -11,7 +11,7 @@ _None_
 ### New Features
 
 - Added `find_or_create_pull_request` action and `GithubHelper#find_pull_request`: returns the URL of the open Pull Request for a head branch, creating one only if none exists yet. Useful for "rolling" automations (e.g. a daily translations or dependency-update job) that force-push the same head branch on every run. [#733]
-- Added `ios_generate_pot_from_stringsdict` and `ios_generate_stringsdict_from_po` actions to round-trip iOS `.stringsdict` plural files through a gettext `.po`/`.pot`-based translation system (e.g. GlotPress). The forward action turns an English `.stringsdict` into a `.pot` template (one `msgid`/`msgid_plural` per plural variable); the reverse rebuilds a per-locale `.stringsdict` from a translated `.po`, mapping gettext's indexed plural forms back to CLDR plural categories (`one`/`few`/`many`/…) via the new `Ios::PluralRules` table and using the English `.stringsdict` as a structural template. [#739]
+- Added `ios_generate_pot_from_stringsdict` and `ios_generate_stringsdict_from_po` actions to round-trip iOS `.stringsdict` plural files through a gettext `.po`/`.pot`-based translation system (e.g. GlotPress). The forward action turns an English `.stringsdict` into a `.pot` template (one `msgid`/`msgid_plural` per plural variable); the reverse rebuilds a per-locale `.stringsdict` from a translated `.po`, mapping gettext's indexed plural forms back to CLDR plural categories (`one`/`few`/`many`/…) via the new `Ios::PluralRules` table and using the English `.stringsdict` as a structural template. The forward action round-trips only the `one`/`other` forms; other CLDR categories in the source (e.g. a `zero` literal override) are dropped with a warning. [#739]
 
 ### Bug Fixes
 

lib/fastlane/plugin/wpmreleasetoolkit/actions/ios/ios_generate_pot_from_stringsdict.rb

@@ -37,6 +37,13 @@ def self.details
           are keyed by a deterministic `msgctxt` (the `.stringsdict` key for single-variable
           entries, or `key:variable` for entries that reference multiple plural variables).
 
+          Only the `one` and `other` forms are converted. Any other CLDR category in the
+          source — including an explicit `zero` literal override (e.g. "No items" for a
+          count of 0) — has no gettext equivalent, so it is dropped from the `.pot` and a
+          warning is logged. Handle such count-specific messages as dedicated strings
+          selected in code (e.g. `if count == 0`) rather than as `zero`/`two`/… keys in a
+          `.stringsdict` bound for this pipeline.
+
           Use `ios_generate_stringsdict_from_po` to convert the translated `.po` files back
           into per-locale `.stringsdict` files once translation is complete.
         DETAILS

lib/fastlane/plugin/wpmreleasetoolkit/helper/ios/ios_stringsdict_helper.rb

@@ -17,7 +17,10 @@ module Ios
       # **Forward** ({generate_pot}): an English `.stringsdict` becomes a `.pot`
       # template. Each plural variable becomes one `msgid`/`msgid_plural` entry
       # (English `one` → `msgid`, English `other` → `msgid_plural`), keyed by a
-      # deterministic `msgctxt`.
+      # deterministic `msgctxt`. Only `one`/`other` map to gettext; any other CLDR
+      # category present in the source — most notably an explicit `zero` literal
+      # override (which iOS honors even for English, e.g. "No items" for a count
+      # of 0) — has no gettext slot and is dropped from the `.pot` with a warning.
       #
       # **Reverse** ({generate_stringsdict_from_po}): a translated `.po` for a
       # locale, plus the original English `.stringsdict` as a structural template,
@@ -100,7 +103,7 @@ def self.generate_pot(stringsdict_paths:, output_path:)
                         "`#{seen_contexts[context]}`). Stringsdict keys must be unique across the files being converted."
                 end
                 seen_contexts[context] = path
-                entries << build_pot_entry(context: context, var_dict: var_dict, key: key)
+                entries << build_pot_entry(context: context, var_dict: var_dict, key: key, variable: var_name)
               end
             end
           end
@@ -197,14 +200,16 @@ def self.context_for(key:, variable:, single_variable:)
           single_variable ? key : "#{key}:#{variable}"
         end
 
-        def self.build_pot_entry(context:, var_dict:, key:)
+        def self.build_pot_entry(context:, var_dict:, key:, variable:)
           singular = var_dict['one'] || var_dict['other']
           plural = var_dict['other']
           if singular.nil? || plural.nil?
             raise "Stringsdict entry '#{key}' is missing a required plural form " \
                   "(needs at least 'other'; 'one' recommended for the singular)."
           end
 
+          warn_dropped_categories(key: key, variable: variable, var_dict: var_dict)
+
           entry = GetText::POEntry.new(:msgctxt_plural)
           entry.msgctxt = context
           entry.msgid = singular
@@ -214,6 +219,26 @@ def self.build_pot_entry(context:, var_dict:, key:)
           entry
         end
 
+        # Only `one`/`other` survive the gettext round-trip (as `msgid`/
+        # `msgid_plural`). Any other CLDR category in the source variable — most
+        # commonly a `zero` literal override, which iOS honors even for English
+        # (Apple's docs: an English `zero` returns "No homes found" for `0`) — has
+        # no gettext equivalent and is dropped from the `.pot`. Warn so it isn't
+        # lost silently.
+        def self.warn_dropped_categories(key:, variable:, var_dict:)
+          dropped = (CLDR_CATEGORIES - %w[one other]) & var_dict.keys
+          return if dropped.empty?
+
+          UI.important(
+            "Stringsdict entry '#{key}' (variable '#{variable}') has plural form(s) " \
+            "[#{dropped.join(', ')}] that gettext can't represent — they will be dropped " \
+            "from the `.pot` and won't be translated. Only 'one' and 'other' round-trip; " \
+            "handle a count-specific message (e.g. a 'zero'/empty-state string) as a dedicated " \
+            'string selected in code (`if count == 0`), not as a plural key in a `.stringsdict` ' \
+            'bound for this pipeline.'
+          )
+        end
+
         # The translated plural forms for a context, or `[]` if untranslated.
         def self.translated_forms(parsed_po:, context:, source_var:)
           msgid = source_var['one'] || source_var['other']

spec/ios_stringsdict_helper_spec.rb

@@ -132,6 +132,43 @@ def convert_po_to_stringsdict(po_content, template:, locale:)
           .to raise_error(/missing a required plural form/)
       end
     end
+
+    it 'warns and drops source plural forms other than one/other (e.g. a `zero` override)' do
+      in_tmp_dir do |dir|
+        src = File.join(dir, 'zero.stringsdict')
+        described_class.write(
+          data: {
+            'homes' => {
+              'NSStringLocalizedFormatKey' => '%#@count@',
+              'count' => {
+                'NSStringFormatSpecTypeKey' => 'NSStringPluralRuleType',
+                # iOS honors an English `zero` override (Apple: returns "No homes found" for 0),
+                # but gettext has no slot for it — so it must be dropped *loudly*.
+                'zero' => 'No homes found',
+                'one' => '%d home found',
+                'other' => '%d homes found'
+              }
+            }
+          },
+          path: src
+        )
+        pot = File.join(dir, 'out.pot')
+
+        expect(FastlaneCore::UI).to receive(:important) do |message|
+          expect(message).to include('zero')
+          expect(message).to match(/drop/i)
+        end
+
+        described_class.generate_pot(stringsdict_paths: src, output_path: pot)
+
+        content = File.read(pot)
+        # `one`/`other` still convert…
+        expect(content).to include('msgid "%d home found"')
+        expect(content).to include('msgid_plural "%d homes found"')
+        # …but the `zero` literal override is dropped.
+        expect(content).not_to include('No homes found')
+      end
+    end
   end
 
   describe '.generate_stringsdict_from_po' do