fix: preserve ICU exact-match plural selectors (=0, =1) in export

[peterzen]

Two related issues caused push→pull round-trips to produce file diffs:

1. IcuToGenericFormatMessageConvertor.convert() called toIcuPluralString() without optimize=false, relying on the default optimize=true. This triggered optimizePluralForms + orderPluralForms on every export, silently reordering or removing plural forms that the user authored.

2. orderPluralForms sorted unknown keys (including =0, =1, =2 exact-match selectors) alphabetically after 'other', placing them last instead of first. ICU exact-match selectors should precede keyword selectors and appear in ascending numeric order.

Fix: pass optimize=false in the export path so the stored ICU string is emitted verbatim. Also update orderPluralForms to sort =N selectors before keyword forms in numeric order so that explicit optimize calls produce canonical output consistent with the ICU specification.

Fixes: #3267

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed plural form ordering for translations with exact-match selectors (e.g., =1, =0). These selectors now correctly appear before keyword-based plural forms and are sorted in ascending numeric order.

[coderabbitai]

📝 Walkthrough

Walkthrough

These changes fix plural form handling by preventing automatic optimization of plural forms with exact-match selectors (e.g., =0, =1) and implementing proper ordering to preserve their sequence during import and export operations.

Changes

Cohort / File(s)	Summary
Plural Form Ordering Logic backend/data/src/main/kotlin/io/tolgee/formats/pluralFormsUtil.kt, backend/data/src/main/kotlin/io/tolgee/formats/generic/IcuToGenericFormatMessageConvertor.kt	Refactored orderPluralForms to implement two-level sorting: exact-match selectors (keys starting with =) sorted numerically first, followed by keyword forms sorted by formKeywords position. Disabled automatic optimization in conversion path by passing optimize = false to toIcuPluralString.
Plural Form Tests backend/data/src/test/kotlin/io/tolgee/unit/formats/PluralsFormUtilTest.kt	Added comprehensive test coverage for exact-match selector ordering, numeric sorting of multiple =N forms, preservation of exact-match selectors during optimization, and round-trip parsing/serialization validation.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• Anty0
• JanCizmar

Poem

🐰 A plural tale of ordering true,
Exact matches now sort first in view,
No optimization shadows the way,
Forms preserved both night and day,
Tolgee's translations shine bright and new! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: preserve ICU exact-match plural selectors (=0, =1) in export' clearly and concisely summarizes the main change: preserving exact-match selectors in plural exports.
Linked Issues check	✅ Passed	The PR directly addresses issue #3267 by fixing both root causes: disabling optimization on export (optimize=false) and correcting orderPluralForms to place exact-match selectors before keywords in numeric order.
Out of Scope Changes check	✅ Passed	All changes are scoped to the exact-match plural selector preservation fix: modified export behavior, updated sorting logic, and added comprehensive test coverage for the new behavior.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

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📝 Coding Plan

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[coderabbitai]

🧹 Nitpick comments (1)

backend/data/src/test/kotlin/io/tolgee/unit/formats/PluralsFormUtilTest.kt (1)

56-61: Consider using a single combined assertion for clearer test failure messages.

The separate assert calls could be consolidated to improve readability and provide a more informative failure message.

♻️ Optional: Combine ordering assertions

-    assert(output.indexOf("=0") < output.indexOf("one")) {
-      "=0 should come before 'one' in: $output"
-    }
-    assert(output.indexOf("=0") < output.indexOf("other")) {
-      "=0 should come before 'other' in: $output"
-    }
+    val idx0 = output.indexOf("=0")
+    val idxOne = output.indexOf("one")
+    val idxOther = output.indexOf("other")
+    assert(idx0 < idxOne && idx0 < idxOther) {
+      "=0 (at $idx0) should come before 'one' (at $idxOne) and 'other' (at $idxOther) in: $output"
+    }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@backend/data/src/test/kotlin/io/tolgee/unit/formats/PluralsFormUtilTest.kt`
around lines 56 - 61, Replace the two separate assert calls that check ordering
of "=0" vs "one" and "other" with a single combined assertion in
PluralsFormUtilTest that verifies both conditions at once (e.g. check
output.indexOf("=0") < output.indexOf("one") && output.indexOf("=0") <
output.indexOf("other")) and provide a clear failure message that includes the
output and the three indices so test failures show the full ordering info;
update the assertion surrounding the variable output accordingly.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@backend/data/src/test/kotlin/io/tolgee/unit/formats/PluralsFormUtilTest.kt`:
- Around line 56-61: Replace the two separate assert calls that check ordering
of "=0" vs "one" and "other" with a single combined assertion in
PluralsFormUtilTest that verifies both conditions at once (e.g. check
output.indexOf("=0") < output.indexOf("one") && output.indexOf("=0") <
output.indexOf("other")) and provide a clear failure message that includes the
output and the three indices so test failures show the full ordering info;
update the assertion surrounding the variable output accordingly.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 72b94f01-7844-4b10-8f40-3d2eaf2917b0

📥 Commits

Reviewing files that changed from the base of the PR and between b7ad9f2 and 847a382.

📒 Files selected for processing (3)

• backend/data/src/main/kotlin/io/tolgee/formats/generic/IcuToGenericFormatMessageConvertor.kt
• backend/data/src/main/kotlin/io/tolgee/formats/pluralFormsUtil.kt
• backend/data/src/test/kotlin/io/tolgee/unit/formats/PluralsFormUtilTest.kt

[JanCizmar]

Hey! Thanks a lot for the PR. @Anty0 can you please review this?