[messages] Fix incomplete translations, reordered placeholders, and placeholders next to plurals by mosuem · Pull Request #1120 · dart-lang/i18n

mosuem · 2026-10-30T07:45:19Z

Note

This PR was generated by an AI coding agent (Jetski) on behalf of @mosuem.

Fixes several bugs that make translated messages render incorrectly. They all
show up as soon as translations come from a translation pipeline, where
translations are often incomplete and reorder placeholders.

Bugs

Case	Before	After
A translation is missing a message (`fr.arb` has no `banana`)	Lookups after the gap shift: `banana` returns "Cerise", `cherry` throws a `RangeError`	Falls back to the template's message
A translation has a message which is not in the template	Same shift	Dropped, with a warning
A translation reorders placeholders (`Bonjour {last} {first}`)	`Bonjour Ada Lovelace`	`Bonjour Lovelace Ada`
A message mixes placeholders with a plural or select (`{name} has {count, plural, ...}`)	The placeholder is dropped: `has 3 messages`	`Ada has 3 messages`
A `cleaner` on a message with arguments	Ignored, or a `RangeError` if it changes the length	Applied to each literal segment, arguments are untouched

Changes

messages_builder: groupIntoFamilies (new, lib/message_family.dart)
groups the ARB files by context and aligns every translation with its
template: the same messages in the same order (missing ones fall back to
the template, extra ones are dropped), with argument indices remapped to the
template's placeholder order. Both the data file builder and the code
generator use it, so data files and generated code agree.
messages_builder: all data files of a context now share a hash of the
template's message names and placeholders. Updating a translation no longer
changes the generated code; changing the template's API still does.
messages_builder: MessageParser.parseNode combines text and placeholders
next to plurals and selects into StringMessages, instead of dropping the
placeholders.
messages: StringMessage.generateString applies the cleaner to each
literal segment.
Regenerated pkgs/messages/example; only the hashes change.

The commits can be reviewed one by one.

Testing

New tests: messages/test/string_message_test.dart,
messages_builder/test/message_parser_test.dart, and
messages_builder/test/message_family_test.dart. The cleaner and parser
tests fail on main.
dart analyze --fatal-infos, dart format, and dart test pass for
messages, messages_builder, messages_serializer, and
messages_shrinker. The example regenerates without a diff and runs.

Notes

The package:messages workflow currently fails on main because of an
unrelated info in examples_flutter/my_application/lib/main.dart
(package:flutter/material.dart is deprecated on Flutter beta).
This overlaps with the draft Update messages #1081, which touches the same files in
messages_builder. I will rebase that one on top of this.

The cleaner was ignored for messages with arguments, and threw a RangeError if it changed the length of the text. It is now applied to each literal segment, and the arguments are inserted unchanged.

Placeholders were dropped from messages which also contain a plural or select at the same level, such as `{name} has {count, plural, ...}`. Text and placeholders between plurals and selects are now combined into StringMessages.

The generated code looks up messages by their index in the template and passes arguments in the order of the template's placeholders, but each data file was serialized on its own. So a translation which was missing a message, or had an extra one, returned the wrong messages, and a translation which reordered placeholders got the wrong arguments. Translations are now aligned with their template: missing messages fall back to the template, extra messages are dropped, and argument indices are remapped to the template's placeholder order. All data files of a context now share a hash of the template's message names and placeholders, so updating a translation does not change the generated code.

gemini-code-assist · 2026-10-30T07:45:31Z

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses several critical issues in the message translation pipeline, specifically targeting incorrect rendering caused by incomplete translations, reordered placeholders, and complex message structures involving plurals or selects. By introducing a family-based alignment system, the builder now ensures that all translations strictly adhere to the template's structure and argument ordering. Additionally, the parser and generator logic have been improved to correctly handle placeholders adjacent to conditional logic and to ensure deterministic code generation.

Highlights

Message Alignment: Introduced groupIntoFamilies to align translation files with their templates, ensuring consistent message ordering, handling missing messages via fallback, and dropping extraneous entries.
Placeholder Handling: Fixed bugs where placeholders were dropped when appearing alongside plurals or selects, and ensured argument indices are correctly remapped when translations reorder placeholders.
Deterministic Generation: Updated data file hashing to depend only on template structure, preventing unnecessary code regeneration when only translations are updated.
Message Cleaning: Updated StringMessage.generateString to apply cleaners to literal segments individually, preserving argument integrity.

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github-actions · 2026-10-30T07:46:39Z

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// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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gemini-code-assist

Code Review

This pull request aligns translations with their templates to ensure consistent message ordering, correct argument indexing (even when placeholders are reordered), and stable hashes that only depend on the template's structure. It also fixes an issue where placeholders were dropped from messages containing plurals or selects, and updates StringMessage.generateString to apply the cleaner function to each literal segment. Feedback highlights a potential non-determinism issue in groupIntoFamilies due to file system loading order, which could lead to flaky builds and unstable generated filenames; sorting the files by path is recommended to ensure deterministic builds.

gemini-code-assist · 2026-10-30T07:47:47Z

+List<MessageFamily> groupIntoFamilies(
+  List<LocatedMessageFile> messageFiles, {
+  void Function(String message)? warn,
+}) {
+  final groups = messageFiles
+      .groupListsBy((messageFile) => findTemplate(messageFiles, messageFile));
+  return [
+    for (final MapEntry(key: template, value: members) in groups.entries)
+      _alignFamily(template, members, warn),
+  ];
+}


The order of messageFiles can be non-deterministic because it is loaded from the file system (via Directory.list()). This non-determinism can propagate to the order of MessageFamily groups returned by groupIntoFamilies. In builder.dart, if the message context is null, the generator uses a counter to name the files (e.g., m${counter++}_messages.g.dart). A non-deterministic family order will result in non-deterministic filenames across builds, causing flaky builds and unnecessary git diffs. Sorting messageFiles by their path at the beginning of groupIntoFamilies ensures deterministic grouping and file generation.

Suggested change

List<MessageFamily> groupIntoFamilies(

List<LocatedMessageFile> messageFiles, {

void Function(String message)? warn,

}) {

final groups = messageFiles

.groupListsBy((messageFile) => findTemplate(messageFiles, messageFile));

return [

for (final MapEntry(key: template, value: members) in groups.entries)

_alignFamily(template, members, warn),

];

}

List<MessageFamily> groupIntoFamilies(

List<LocatedMessageFile> messageFiles, {

void Function(String message)? warn,

}) {

final sortedFiles = messageFiles.toList()..sortBy((file) => file.path);

final groups = sortedFiles

.groupListsBy((messageFile) => findTemplate(sortedFiles, messageFile));

return [

for (final MapEntry(key: template, value: members) in groups.entries)

_alignFamily(template, members, warn),

];

}

mosuem added 4 commits October 30, 2026 07:44

[messages] Apply the cleaner to each literal segment of a StringMessage

757dae3

The cleaner was ignored for messages with arguments, and threw a RangeError if it changed the length of the text. It is now applied to each literal segment, and the arguments are inserted unchanged.

[messages] Regenerate the example

dcbe744

github-actions Bot added package:messages package:messages_builder labels Oct 30, 2026

gemini-code-assist Bot reviewed Oct 30, 2026

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mosuem mentioned this pull request Oct 30, 2026

Add resource identifiers to package:messages #844

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[messages] Fix incomplete translations, reordered placeholders, and placeholders next to plurals - #1120

[messages] Fix incomplete translations, reordered placeholders, and placeholders next to plurals#1120
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fixTranslationAlignment

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mosuem commented Oct 30, 2026

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