excel_translator 2.1.6

Generate type-safe Flutter localizations from Excel, CSV, and ODS files with multi-sheet support and automatic validation.

excel_translator

Generate type-safe Flutter/Dart localizations from Excel, CSV, or ODS files. Organize translations by feature using sheets, get compile-time safety and auto-completion, and choose between a flexible CLI or a convenient build_runner integration.

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Table of Contents

• Introduction
• Features
• Installation
• Quick Start
• Excel Structure
• CLI Mode
• build_runner Mode
• Why build_runner Output Differs from CLI Output
• Recommended Workflow
• Best Practices
• Performance Notes
• Architecture Overview
• Migration Notes
• FAQ
• Deal Breakers / Important Limitations

---

Introduction

excel_translator generates Dart localization classes directly from spreadsheet files. Instead of managing .arb files or hand-rolling localization boilerplate, you maintain a single Excel workbook where each sheet represents a localization module (e.g., login, home, buttons).

The package supports two generation modes:

Mode	Primary use case
CLI	Advanced projects, per-sheet file output, CI pipelines, full control
build_runner	Convenience, watch mode, simple projects that can accept a single merged output

Both modes produce type-safe Dart code from the same Excel source. They differ in how many files they emit and whether dynamic per-sheet filenames are possible — this distinction is explained in detail below.

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Features

• Multi-format support — Excel (.xlsx), CSV (.csv), and ODS (.ods)
• Multi-sheet support — Organize translations by feature (Excel & ODS)
• Type-safe generated code — Compile-time safety with IDE auto-completion
• String interpolation — Dynamic values via {variable} or %variable$s syntax
• 184+ language codes — Full ISO 639-1 with country variants (en_US, pt_BR, zh_CN)
• CamelCase accessors — app_title → .appTitle
• Language validation — Validates codes at generation time with clear error messages
• Zero-config CLI — Reads configuration from pubspec.yaml
• Global instance — Access translations outside BuildContext (services, repositories)
• Watch mode — Re-generates automatically on file change via build_runner

Format Comparison

Format	Extension	Multi-sheet	Best for
Excel	.xlsx	Yes	Complex projects with many modules
CSV	.csv	No	Simple projects, single-language modules
ODS	.ods	Yes	Teams using LibreOffice Calc

---

Installation

Add to pubspec.yaml:

dependencies:
  excel_translator: ^2.1.6

For build_runner integration, also add to dev_dependencies:

dev_dependencies:
  build_runner: ^2.4.0

Then run:

dart pub get

---

Quick Start

1. Create Your Spreadsheet

Excel (.xlsx) with multiple sheets:

Sheet login:

key	en	id	es
title	Login	Masuk	Iniciar sesión
forgot_password	Forgot Password?	Lupa Kata Sandi?	¿Olvidó su contraseña?
welcome_message	Welcome {name}!	Selamat datang {name}!	¡Bienvenido {name}!

Sheet buttons:

key	en	id	es
submit	Submit	Kirim	Enviar
cancel	Cancel	Batal	Cancelar

CSV (.csv) — single sheet only:

key,en,id,es
title,Login,Masuk,"Iniciar sesión"
forgot_password,Forgot Password?,Lupa Kata Sandi?,¿Olvidó su contraseña?

2. Configure pubspec.yaml

excel_translator:
  excel_file: assets/localizations.xlsx   # .xlsx, .csv, or .ods
  output_dir: lib/generated
  class_name: AppLocalizations            # optional, default: AppLocalizations
  include_flutter_delegates: true         # optional, default: true

3. Generate

# CLI mode (recommended)
dart run excel_translator

# build_runner mode
dart run build_runner build

4. Use in Your App

import 'lib/generated/generated_localizations.dart';

// In a widget
final loc = AppLocalizations.of(context);
print(loc.login.title);                           // "Login"
print(loc.login.forgotPassword);                  // "Forgot Password?"
print(loc.login.welcomeMessage(name: 'Alice'));   // "Welcome Alice!"
print(loc.buttons.submit);                        // "Submit"

// By language code
final id = AppLocalizations('id');
print(id.login.title);   // "Masuk"

// Named getters (first 5 languages in your workbook)
AppLocalizations.english.login.title;
AppLocalizations.en.login.title;

// System language auto-detection (no BuildContext needed)
AppLocalizations.current.login.title;

5. Flutter App Setup

MaterialApp(
  localizationsDelegates: AppLocalizations.delegates,
  supportedLocales: AppLocalizations.supportedLanguages
      .map((code) => Locale(code))
      .toList(),
  home: const MyHomePage(),
);

---

Excel Structure

Single-sheet workbook

One sheet with any name. All translations live in one class.

key	en	id
app_title	My App	Aplikasi Saya
save_button	Save	Simpan

Multi-sheet workbook

Each sheet becomes its own class, accessible as a named property on AppLocalizations.

Sheet home:

key	en	id
greeting	Good morning!	Selamat pagi!
subtitle	What would you like to do?	Apa yang ingin Anda lakukan?

Sheet errors:

key	en	id
network_error	No internet connection	Tidak ada koneksi internet
not_found	Resource not found	Sumber daya tidak ditemukan

Accessed as:

loc.home.greeting
loc.errors.networkError

Rules

• First column must be key
• Remaining columns are language codes (en, id, es, pt_BR, …)
• Language codes are validated against ISO 639-1 at generation time
• Empty rows are skipped
• Sheet names become class names and property names (sanitized to camelCase)

---

CLI Mode

How it Works

The CLI reads your spreadsheet, parses every sheet, and writes one .dart file per sheet plus a main entry-point file. The main file imports each sheet file and composes them into a single AppLocalizations class.

┌─────────────────────────────┐
│  localizations.xlsx         │
│  ├── sheet: login           │
│  ├── sheet: buttons         │
│  └── sheet: errors          │
└──────────────┬──────────────┘
               │  dart run excel_translator
               ▼
┌─────────────────────────────────────────┐
│  lib/generated/                         │
│  ├── generated_localizations.dart       │  ← main class + imports
│  ├── build_context_extension.dart       │  ← context.loc extension
│  ├── login_localizations.dart           │  ← LoginLocalizations class
│  ├── buttons_localizations.dart         │  ← ButtonsLocalizations class
│  └── errors_localizations.dart          │  ← ErrorsLocalizations class
└─────────────────────────────────────────┘

Commands

# Zero-config — reads pubspec.yaml
dart run excel_translator

# Explicit file and output dir
dart run excel_translator assets/localizations.xlsx lib/generated

# Custom class name
dart run excel_translator assets/localizations.xlsx lib/generated --class-name=L10n

# Disable Flutter delegates (pure Dart projects)
dart run excel_translator assets/localizations.xlsx lib/generated --no-delegates

# Show current configuration
dart run excel_translator log

# Show help
dart run excel_translator --help

# Show version
dart run excel_translator --version

Global installation (run from any directory):

dart pub global activate excel_translator

excel_translator                                          # pubspec.yaml config
excel_translator assets/localizations.xlsx lib/generated
excel_translator assets/l10n.csv lib/generated --class-name=L10n

dart pub global deactivate excel_translator              # uninstall

Options

Flag	Short	Default	Description
--class-name=NAME	-c=NAME	AppLocalizations	Generated root class name
--no-delegates	-nd	—	Omit Flutter delegates
--delegates=BOOL	-d=BOOL	true	Toggle delegates
--help	-h	—	Show help
--version	-v	—	Show version

Generated Output Structure (CLI)

lib/generated/
├── generated_localizations.dart     # Root class — imports all sheet files
├── build_context_extension.dart     # Optional BuildContext extension
├── login_localizations.dart         # One file per sheet
├── buttons_localizations.dart
└── errors_localizations.dart

generated_localizations.dart imports the sheet files:

// GENERATED CODE - DO NOT MODIFY BY HAND
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:excel_translator/excel_translator.dart';
import 'dart:ui' show PlatformDispatcher;

import 'login_localizations.dart';
import 'buttons_localizations.dart';
import 'errors_localizations.dart';

class AppLocalizations { ... }
class AppLocalizationsDelegate extends LocalizationsDelegate<AppLocalizations> { ... }

CLI Advantages

• Per-sheet files keep diffs small and readable in code review
• Sheet files can be individually inspected or linted
• Full control over when generation runs
• Works in CI pipelines without build_runner overhead
• Supports all CLI flags not available in build_runner
• No constraints on output file naming

---

build_runner Mode

When to Use It

Use build_runner when you want automatic regeneration on file save during development — the watch mode integration is its main value. It is not a replacement for CLI mode in production pipelines.

Setup

1. Add build_runner to dev_dependencies (already shown in Installation).
2. Ensure pubspec.yaml has an excel_translator section with at least excel_file and output_dir.

The package ships a build.yaml that registers the builder automatically for the root package — no manual build.yaml changes are required in your project.

Your pubspec.yaml:

excel_translator:
  excel_file: assets/localizations.xlsx
  output_dir: lib/generated
  class_name: AppLocalizations           # optional
  include_flutter_delegates: true        # optional

Commands

# One-time build
dart run build_runner build

# Watch mode — regenerates on Excel file change
dart run build_runner watch

# Force rebuild (clears cache)
dart run build_runner build --delete-conflicting-outputs

Generated Output Structure (build_runner)

lib/generated/
├── generated_localizations.dart     # All sheet classes inlined here
└── build_context_extension.dart     # Optional BuildContext extension

All sheet classes are inlined into generated_localizations.dart. There are no separate per-sheet files.

// GENERATED CODE - DO NOT MODIFY BY HAND
import 'package:flutter/material.dart';
...

class LoginLocalizations { ... }    // inlined
class ButtonsLocalizations { ... }  // inlined
class ErrorsLocalizations { ... }   // inlined

class AppLocalizations { ... }
class AppLocalizationsDelegate { ... }

build_runner Limitations

• Always produces exactly 2 output files regardless of sheet count
• Per-sheet file output is not possible (see Why build_runner Output Differs)
• output_dir must match the hardcoded lib/generated path (the build extensions are declared statically)
• No support for --class-name or --no-delegates flags at build time; configure via pubspec.yaml instead
• All build_runner constraints apply: outputs must be under lib/, cannot write outside the package

---

Why build_runner Output Differs from CLI Output

This is the most important architectural difference to understand.

The Core Constraint

build_runner requires every builder to declare its output files before the build runs. This declaration is called buildExtensions and it must be a static, compile-time constant:

@override
final buildExtensions = const {
  'pubspec.yaml': [
    'lib/generated/generated_localizations.dart',
    'lib/generated/build_context_extension.dart',
  ],
};

This is how build_runner constructs its asset graph, tracks dependencies, and decides which builders to invalidate on change. The output file list cannot be computed dynamically.

Why Per-Sheet Files Are Not Possible

To generate per-sheet files, the builder would need to declare output names like:

// This is NOT possible in build_runner
'lib/generated/login_localizations.dart',
'lib/generated/buttons_localizations.dart',
'lib/generated/errors_localizations.dart',

But sheet names (login, buttons, errors) are only known after parsing the Excel file — which happens inside the build() method at runtime, long after buildExtensions has been evaluated.

Timeline:
  build graph construction → buildExtensions evaluated   ← sheet names unknown here
  build execution          → build() called, Excel parsed ← sheet names known here

There is no mechanism in the build package to emit files with names determined at runtime. Any attempt to write to an undeclared asset path would be rejected by the build system.

The Solution: Inline Mode

The builder resolves this by inlining all sheet classes into a single file with a deterministic, pre-declared name (generated_localizations.dart). The content is dynamic; the filename is not. This satisfies build_runner's requirements while still producing fully functional generated code.

CLI Has No Such Constraint

The CLI runs as a plain Dart script with full filesystem access. It parses the Excel file first, discovers sheet names, then writes one file per sheet. The output list is determined at runtime — exactly what build_runner disallows.

---

Recommended Workflow

For Most Projects

Use CLI mode as the primary workflow.

# Add to pubspec.yaml, then run:
dart run excel_translator

Re-run whenever you update your Excel file. This fits naturally into existing workflows: run before committing, add to CI, or wire to a Makefile / justfile target.

For Active Development (watch mode)

Use build_runner watch during development for automatic regeneration:

dart run build_runner watch

Accept the trade-off: output will be a single merged file instead of per-sheet files. Switch back to CLI mode before committing if per-sheet output is required.

Mixed Workflow

A practical pattern for teams:

1. Use build_runner watch locally during active translation work
2. Run dart run excel_translator in CI to produce the canonical per-sheet output
3. Commit the CLI-generated files

This avoids friction locally while keeping clean, reviewable per-sheet diffs in version control.

---

Best Practices

Spreadsheet organization

• Group related keys into the same sheet (e.g., one sheet per feature screen)
• Use consistent key naming: snake_case throughout
• Keep keys short and self-documenting: login_title not lt
• Add a fallback language column (usually en) as the first language column

Key naming

• Keys become method or getter names after camelCase conversion
• Avoid Dart reserved words as key names (class, void, return, etc.)
• String interpolation keys: welcome_message with value Welcome {name}! → welcomeMessage(name: ...)

Version control

• Commit the generated files; do not .gitignore them
• This ensures the app builds without running the generator and makes diffs reviewable
• Generated files are clearly marked // GENERATED CODE - DO NOT MODIFY BY HAND

CI integration

# Example CI step (GitHub Actions)
- name: Generate localizations
  run: dart run excel_translator

- name: Check for uncommitted changes
  run: git diff --exit-code lib/generated/

Multiple environments

• Keep one authoritative Excel file in the repository under assets/
• Avoid maintaining parallel CSV exports — they will drift from the source

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Performance Notes

• Parse time scales with workbook size, not sheet count. A 50-sheet workbook with 20 keys each parses faster than a 1-sheet workbook with 10,000 keys.
• Generation time is negligible; the bottleneck is always parsing.
• build_runner adds overhead per build due to asset graph evaluation. For large projects, dart run excel_translator is faster for one-off generation.
• Watch mode only re-parses when the Excel file changes (the asset is registered as a build dependency), so incremental rebuilds are fast.
• Generated code uses switch statements per key, not maps. This is intentional: switch compiles to jump tables, avoids heap allocation, and performs better under tree-shaking.

---

Architecture Overview

excel_translator/
├── bin/
│   └── excel_translator.dart        # CLI entry point
│
├── lib/
│   ├── builder.dart                 # build_runner Builder implementation
│   ├── cli.dart                     # Public CLI API
│   ├── excel_translator.dart        # Public library exports
│   │
│   └── src/
│       ├── cli.dart                 # ExcelTranslatorCLI — argument parsing
│       ├── translator_service.dart  # Orchestration layer
│       │
│       ├── parsers/
│       │   ├── file_parser_interface.dart   # FileParser interface
│       │   ├── parser_factory.dart          # Format detection
│       │   ├── excel_parser.dart            # .xlsx via table_parser
│       │   ├── csv_parser.dart              # .csv (RFC 4180 + quoted commas)
│       │   └── ods_parser.dart              # .ods via table_parser
│       │
│       ├── generators/
│       │   ├── sheet_class_generator.dart   # Per-sheet class generation
│       │   ├── main_class_generator.dart    # Root AppLocalizations class
│       │   └── extension_generator.dart     # BuildContext extension
│       │
│       ├── services/
│       │   ├── config_service.dart          # pubspec.yaml config loading
│       │   └── language_service.dart        # ISO 639-1 validation + names
│       │
│       ├── models/
│       │   ├── localization_sheet.dart      # Sheet + translations model
│       │   ├── translation.dart             # Key + language map
│       │   ├── language.dart                # Language metadata
│       │   └── config.dart                  # Configuration model
│       │
│       └── utils/
│           ├── string_utils.dart            # camelCase, sanitization
│           ├── validators.dart              # Input validation
│           ├── logger.dart                  # Structured output
│           └── errors.dart                  # Typed exceptions

Data Flow

Excel/CSV/ODS file
       │
       ▼
  FileParserFactory.createParser()
       │  selects parser by file extension
       ▼
  FileParser.parseFile() / parseFileFromBytes()
       │  produces List<LocalizationSheet>
       ▼
  Generators (SheetClassGenerator, MainClassGenerator, ExtensionGenerator)
       │
       ├─── CLI mode  → writes N+2 files (N sheets + main + extension)
       │
       └─── Builder   → writes 2 files (inline merged + extension)

Generator Modes Side by Side

CLI mode                          build_runner mode
─────────────────────────────     ─────────────────────────────
login_localizations.dart          ┐
buttons_localizations.dart        │ inlined into
errors_localizations.dart         ┘ generated_localizations.dart
generated_localizations.dart      generated_localizations.dart
build_context_extension.dart      build_context_extension.dart

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Migration Notes

From 2.0.x to 2.1.x

• Dart SDK minimum raised to >=3.8.0. Update your pubspec.yaml environment constraint if needed.
• build_runner mode now inlines all sheet classes into generated_localizations.dart. If you were importing per-sheet files generated by a previous build_runner run, update those imports to point to generated_localizations.dart instead.
• initializeGlobal(), initializeGlobalWithLanguage(), and related global instance methods have been removed in favour of AppLocalizations.current and the constructor AppLocalizations(languageCode). Replace call sites accordingly.
• CSV parser now correctly handles commas inside quoted fields (RFC 4180 compliance).

From 1.x to 2.x

• Configuration moved from CLI flags to pubspec.yaml. The excel_translator section is now the canonical configuration source.
• Sheet name sanitization changed: hyphens and spaces in sheet names are now converted to underscores before camelCasing. A sheet named My Sheet becomes .mySheet, not .mysheet. Audit your access sites.
• The global executable name is now excel_translator (previously varied by install method). Update scripts accordingly.

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FAQ

Can I use this without Flutter?

Yes. Pass --no-delegates to the CLI or set include_flutter_delegates: false in pubspec.yaml. The generated classes have no Flutter dependency and work in any Dart project.

Does CSV support multiple sheets?

No. CSV is a single-sheet format. Use Excel or ODS if you need per-module organization.

Can I customise the output directory in build_runner mode?

Partially. You can set output_dir in pubspec.yaml, but it must be lib/generated. The builder's buildExtensions declares the output paths statically. Changing output_dir to a different value in pubspec.yaml affects the content of the generated file but not its location on disk — the file is always written to lib/generated/.

Can I run both CLI and build_runner in the same project?

Yes, but they will both write to lib/generated/. CLI generates per-sheet files; build_runner generates a single merged file. Running one after the other will leave stale files from whichever ran first. Pick one mode as canonical and delete the other's outputs.

Why are language getters only generated for the first 5 languages?

Named getters like AppLocalizations.english and AppLocalizations.en are generated for the first 5 language codes found in the workbook, to avoid unbounded code growth. All languages remain accessible via the constructor: AppLocalizations('pt_BR').

How do I add a new language?

Add a new column to your Excel sheet with the ISO 639-1 language code as the header. Re-run the generator. The new language appears in supportedLanguages and is immediately accessible.

What happens if a translation is missing for a key?

The generated switch statement includes a default: case that falls back to the first language value found for that key (typically en). No exception is thrown.

Can I rename the root class from AppLocalizations?

Yes. Use --class-name=MyL10n with the CLI or set class_name: MyL10n in pubspec.yaml.

Are the generated files safe to commit?

Yes, and it is recommended. Committing generated files means your project builds without requiring contributors to run the generator, and generated diffs are reviewable in pull requests.

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Deal Breakers / Important Limitations

Read this section before choosing build_runner mode for a production project.

build_runner Cannot Generate Per-Sheet Files

This is a fundamental, non-negotiable constraint of the build package — not a bug or a missing feature in excel_translator.

The build_runner asset graph requires that every builder declares its output files statically, before any code runs. Sheet names exist only inside the Excel binary. There is no way to declare login_localizations.dart as an output before reading the file, because the string "login" is only discovered during parsing.

There is no workaround. Per-sheet file output requires the CLI.

build_runner output_dir Is Effectively Fixed at lib/generated

The buildExtensions map in builder.dart is declared as a Dart const. The paths lib/generated/generated_localizations.dart and lib/generated/build_context_extension.dart are hardcoded. Setting output_dir to a different value in pubspec.yaml does not change where build_runner writes the files.

If your project requires output in a path other than lib/generated, use CLI mode.

build_runner Mode Is Not Suitable as the Sole Generation Method in CI

build_runner is designed for development-time use. In CI:

• It requires installing build_runner as a dev dependency
• It performs cache invalidation checks that slow down cold builds
• The merged single-file output makes pull request diffs harder to review for translation changes

The CLI is faster, has no extra dependencies, and produces cleaner per-sheet diffs. Use CLI in CI.

Single Excel Workbook Constraint

Both modes consume a single source file. There is no built-in support for merging multiple Excel files into one set of generated classes. If your project needs multi-file sources, merge them at the spreadsheet level before generation.

Sheet Names Drive Public API Shape

Sheet names become Dart class names and property names. Renaming a sheet is a breaking change in the generated API. All call sites (loc.login.title) must be updated. Plan your sheet naming convention early.

Language Names in Getters Are Capped at 5

Named convenience getters (AppLocalizations.english, AppLocalizations.en) are only generated for the first 5 languages. Projects with more than 5 languages should use the constructor (AppLocalizations('fr')) or AppLocalizations.current for all language access beyond the first 5.

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License

MIT