i18n Tooling for the Go Language

This is a general purpose internationalization (i18n) tooling for Go language (Golang) programs. It allows you to prepare Go language code for internationalization and localization (l10n). You can also use it to help maintain the resulting i18n-enabled Golang code so that it remains internationalized. This tool was extracted while working on enabling the Cloud Foundry CLI with i18n support.

This tool is licensed under the Apache 2.0 OSS license. We'd love to hear from you if you are using, attempting to use, or planning to use this tool.

Contact us:

Feel free to open an issue (good or bad) here on Github.
Send email to i18n4go at the Gmail domain.

Getting Started

Overview Presentations, Talks, Blogs

Talk at GoSF Meetup on April, 2015. Slides (PDF and PPTX), demo
Blog post on July, 2015 at IBM's developerWorks: i18n4go: Taking your Golang Projects Global for Fun or Profits

Getting Latest Executable: i18n4go

Assuming you have a valid Golang 1.17.x or later installed for your system, you can quickly get the latest i18n4go executable by running the following go command:

$ go install github.com/maximilien/i18n4go/i18n4go

This will build and place the i18n4go executable built for your operating system in your $GOPATH/bin directory.

Yoiu can also download pre-built executable from the repo's release page.

Cloning and Building

Clone this repo and build it. Using the following commands on a Linux or Mac OS X system:

$ mkdir -p i18n4go/src/github.com/maximilien
$ export GOPATH=$(pwd)/i18n4go:$GOPATH
$ cd i18n4go/src/github.com/maximilien
$ git clone https://github.com/maximilien/i18n4go.git
$ cd i18n4go
$ ./bin/build

NOTE: if you get any dependency errors, then use go get path/to/dependency to get it, e.g., go get github.com/onsi/ginkgo and go get github.com/onsi/gomega

The executable output should now be located in: out/i18n4go. Place it wherever you want, e.g., /usr/local/bin on Linux or Mac OS X.

You can now use the i18n4go executable to issue some of the typical i18n tooling processes.

Running Tests

You should run the tests to make sure all is well, do this with: $ ./bin/test in your cloned repository.

The output should be similar to:

$ bin/test

 Cleaning build artifacts...

 Formatting packages...

 Integration Testing packages:
ok  	github.com/maximilien/i18n4go/integration/checkup	1.571s
ok  	github.com/maximilien/i18n4go/integration/create_translations	1.542s
ok  	github.com/maximilien/i18n4go/integration/extract_strings	1.694s
ok  	github.com/maximilien/i18n4go/integration/fixup	1.657s
ok  	github.com/maximilien/i18n4go/integration/merge_strings	1.645s
ok  	github.com/maximilien/i18n4go/integration/rewrite_package	1.853s
ok  	github.com/maximilien/i18n4go/integration/show_missing_strings	1.590s
?   	github.com/maximilien/i18n4go/integration/test_helpers	[no test files]
ok  	github.com/maximilien/i18n4go/integration/verify_strings	1.701s

 Vetting packages for potential issues...

SWEET SUITE SUCCESS

Typical Workflow

The recommended workflow is to use the commands (documented below) in the following order. For each command, use the command's help or this README for details and to experiment for your project. So the nine steps are:

extract-strings which will automatically extract every string from your Go source files and create a JSON and optionally a PO file.
merge-strings to create one file and removing what is not needed and strings you do not want to i18n. This could be important and time consuming but to help this process, we've found that it's good to keep a list of all the strings that you do not want to i18n as well as string patterns (as regex). Take a look at the CF CLI excluded.json for a real world example file you might end up with. The regex in there might be useful to reuse.
might need to do 1 again, but using excluded.json. The outcome should be the file or files for en_US for all the strings that will be i18n for your app. So for instance, if you decide to combine all into one: en_US.all.json
rewrite-package using the file or files in 3. This will rewrite your code to use the T(...) function and also deal with parameters to your strings, using the pattern: Arg0, Arg1, etc. NOTE that this step will rewrite (yes, modify) your code. You can always use go fmt so the code will look fine. All files that contain strings that need to be i18n will be rewritten. You can do this step one package at a time.
create-translations to create initial translation file or files for each language that you want to support. For instance to create fr_FR file(s) for French and every other locale_Language you specify. This could be done manually. The reason to use tool is optional next step and also because the tool may help streamline your build process... The resulting files can be sent to human translators to be officially completed.
[optional] create-translations with Google Translate API. You will need to have a Google Translate API key (NOTE: might require you to pay or at least enter your credit card if usage is above some threshold). Generally the strings generated by Google Translate are OK, but not great. They usually require additional work, however, we have found that they can be a good start when sending files to be officially translated by human translator team(s).
verify-strings this will help you ensure that your translation files, e.g., en_US.all.json and fr_FR.all.json, and others, all have the same keys. This is important since if you are missing a key then for that language you might crash your app. We recommend using this during your build and for CI and not build resulting app in 8 (next step) if this step fails.
package your app with your i18n resource files. The packaging is slightly tricky since one of the great value of Golang is to have one binary file distribution for your app. This means you need to convert your i18n resource files (the JSON files) into binary that can be loaded in code (as source code). We've been using go-bindata for the CF CLI and that seems to work pretty well. See this script on how we used it in the CF CLI. Other alternatives exist but we have not tried them.
ship and profit :)

Typical Workflow Diagram

Help

Printing the usage help: $ i18n4go . Printing usage help for commands: $ i18n4go <command> --help|-h

usage: i18n4go extract-strings [-vpe] [--dry-run] [--output-flat|--output-match-package|-o <outputDir>] -f <fileName>
   or: i18n4go extract-strings [-vpe] [--dry-run] [--output-flat|--output-match-package|-o <outputDir>] -d <dirName> [-r] [--ignore-regexp <fileNameRegexp>]

usage: i18n4go rewrite-package [-v] [-r] -d <dirName> [--i18n-strings-filename <fileName> | --i18n-strings-dirname <dirName>]
   or: i18n4go rewrite-package [-v] [-r] -f <fileName> --i18n-strings-filename <fileName>

usage: i18n4go merge-strings [-v] [-r] [--source-language <language>] -d <dirName>

usage: i18n4go verify-strings [-v] [--source-language <language>] -f <sourceFileName> --language-files <language files>
   or: i18n4go verify-strings [-v] [--source-language <language>] -f <sourceFileName> --languages <lang1,lang2,...>

usage: i18n4go create-translations [-v] [--google-translate-api-key <api key>] [--source-language <language>] -f <fileName> --languages <lang1,lang2,...> -o <outputDir>

  -h | --help                prints the usage
  -v                         verbose
...

extract-strings

The general usage for extract-strings command is:

  ...
  EXTRACT-STRINGS:

  extract-strings            the extract strings command

  -e                         [optional] the JSON file with strings to be excluded, defaults to excluded.json if present
	-s												 [optional] the JSON file with regexp that specify a capturing group to be extracted instead of the full string matching the regexp

  --po                       to generate standard .po files for translation
  --meta                     [optional] create a *.extracted.json file with metadata such as: filename, directory, and positions of the strings in source file
  --dry-run                  [optional] prevents any output files from being created


  -o                         the output directory where the translation files will be placed
  -f                         the go file name to extract strings
  -d                         the directory containing the go files to extract strings
  -r                         [optional] recursesively extract strings from all subdirectories

  --output-flat              generated files are created in the specified output directory (default)
  --output-match-package     generated files are created in directory to match the package name

  --ignore-regexp            [optional] a perl-style regular expression for files to ignore, e.g., ".*test.*"

The command extract-strings pulls strings out of go files. For the examples below we are running the tool on a copy of the the CloudFoundry CLI cloned in the ./tmp

$ i18n4go extract-strings -v --po -f ./tmp/cli/cf/app/app.go -o ./tmp/cli/i18n -output-match-package

i18n4go: extracting strings from file: ./tmp/cli/cf/app/app.go
Could not find: excluded.json
Loaded 0 excluded strings
Could not find: excluded.json
Loaded 0 excluded regexps
Extracted 10 strings from file: ./tmp/cli/cf/app/app.go
Saving extracted i18n strings to file: tmp/cli/i18n/app/app.go.en.json
Creating and saving i18n strings to .po file: ./tmp/cli/cf/app/app.go.en.po
Total time: 3.962ms

The output for the command above are three files, of which two are important for translation:

a. ./tmp/cli/i18n/app/app.go.en.json

This file is the JSON formatted translation file for English. Some of its content is as follows:

[
  ...
    {
        "id": "Show help",
        "translation": "Show help"
    },
    {
        "id": "%s help [COMMAND]",
        "translation": "%s help [COMMAND]"
    },
  ...
]

b. Optionaly, using -p flag, it will generate ./tmp/cli/i18n/app/app.go.en.po

This file is the PO formatted translation file for English. Some of its content is as follows:

# filename: ../tmp/cli/cf/app/app.go, offset: 1617, line: 48, column: 16
msgid "Show help"
msgstr "Show help"

# filename: ../tmp/cli/cf/app/app.go, offset: 1657, line: 49, column: 28
msgid "%s help [COMMAND]"
msgstr "%s help [COMMAND]"
...

To extract multiples files that are in one directory, use the following:

$ i18n4go extract-strings -v --po -d ./tmp/cli/cf/app/ -o ./tmp/cli/i18n -output-match-package -ignore-regexp ".*test.*"

...

The generated output JSON files are in: ./tmp/cli/i18n/app

merge-strings

The general usage for merge-strings command is:

  ...
  MERGE STRINGS:

  merge-strings              merges multiple <filename>.go.<language>.json files into a <language>.all.json

  -d                         the directory containing the json files to combine
  -r                         [optional] recursesively combine files from all subdirectories

  --source-language          [optional] the source language of the file, typically also part of the file name, e.g., "en_US" (default to 'en')

The command merge-strings combines strings in multiple *.go.[lang].json files generated by Extract Strings into one file. Using the same example source as above.

$ i18n4go merge-strings -v -d ./tmp/cli/i18n/app -source-language en

i18n4go: scanning file: tmp/cli/i18n/app/app.go.en.json
i18n4go: scanning file: tmp/cli/i18n/app/flag_helper.go.en.json
i18n4go: scanning file: tmp/cli/i18n/app/help.go.en.json
i18n4go: saving combined language file: tmp/cli/i18n/app/en.all.json
Total time: 1.283116ms

The output for the command above is one file placed in the same directory as the JSON files being merged: en.all.json. This file containes one formatted translation for each translation generated by extract-strings for English. The -source-language flag must match the language portion of the files in the directory, e.g., app.go.en.json, where the language is "en".

rewrite-package

The general usage for rewrite-package command is:

  ...
  REWRITE-PACKAGE:

  rewrite-package            the rewrite package command

  -f                         the source go file to be rewritten
  -d                         the directory containing the go files to rewrite
  -o                         [optional] output diretory for rewritten file. If not specified, the original file will be overwritten

  --i18n-strings-filename    a JSON file with the strings that should be i18n enabled, typically the output of -extract-strings command
  --i18n-strings-dirname     a directory with the extracted JSON files, using -output-match-package with -extract-strings this directory should match the input files package name
  --root-path                the root path to the Go source files whose packages are being rewritten, defaults to working directory, if not specified

The command rewrite-package will modify the go source files such that every string identified in the JSON translation files are wrapped with the T() function. There are two cases:

a. running it on one source file

$ i18n4go rewrite-package -v -f tmp/cli/cf/app/help.go -i18n-strings-dirname tmp/cli/i18n/app/ -o tmp/cli/cf/app/

i18n4go: rewriting strings for source file: tmp/cli/cf/app/help.go
i18n4go: adding init func to package: app  to output dir: tmp/cli/cf/app
i18n4go: inserting T() calls for strings that need to be translated
saving file to path tmp/cli/cf/app/help.go

Total files parsed: 1
Total extracted strings: 17
Total time: 9.986963ms

b. running it on a directory

$ i18n4go rewrite-package -v -d tmp/cli/cf/app/ -i18n-strings-dirname tmp/cli/i18n/app/ -o tmp/cli/cf/app/

i18n4go: rewriting strings in dir tmp/cli/cf/app/, recursive: false

i18n4go: loading JSON strings from file: tmp/cli/i18n/app/app.go.en.json
i18n4go: rewriting strings for source file: tmp/cli/cf/app/app.go
i18n4go: adding init func to package: app  to output dir: tmp/cli/cf/app
i18n4go: inserting T() calls for strings that need to be translated
saving file to path tmp/cli/cf/app/app.go
i18n4go: loading JSON strings from file: tmp/cli/i18n/app/flag_helper.go.en.json
i18n4go: rewriting strings for source file: tmp/cli/cf/app/flag_helper.go
i18n4go: adding init func to package: app  to output dir: tmp/cli/cf/app
i18n4go: inserting T() calls for strings that need to be translated
saving file to path tmp/cli/cf/app/flag_helper.go
i18n4go: loading JSON strings from file: tmp/cli/i18n/app/help.go.en.json
i18n4go: rewriting strings for source file: tmp/cli/cf/app/help.go
i18n4go: adding init func to package: app  to output dir: tmp/cli/cf/app
i18n4go: inserting T() calls for strings that need to be translated
saving file to path tmp/cli/cf/app/help.go

Total files parsed: 3
Total extracted strings: 21
Total time: 16.648105ms

In both cases above the -i18n-strings-dirname specifies the directory containing the <source.go>.en.json file with the strings to process. However, this can be replaced with -i18n-strings-filename and specify one JSON file (e.g., en.all.json) which contains all the strings.

The result in each case is that the source files are rewritten with the wrapped T() function but also dealing with converting interpolated strings into Go-style templated strings. For instance:

The following interpolated string: "%s help [COMMAND]" is templated to: "{{.Arg0}} help [COMMAND]" and rewritten automaticall as:

T("{{.Arg0}} help [COMMAND]", map[string]interface{}{"Arg0": cf.Name()})

So in essence the strings in the JSON files that where interpolated become templated, that is new IDs for the default language.

create-translations

The general usage for -c create-translations command is:

  ...
  CREATE-TRANSLATIONS:

  create-translations     the create translations command

  -f                         the source translation file
  -o                         the output directory where the newly created translation files will be placed

  --languages                a comma separated list of valid languages with optional territory, e.g., \"en, en_US, fr_FR, es\"
  --source-language          [optional] the source language of the file, typically also part of the file name, e.g., \"en_US\"
  --google-translate-api-key [optional] your public Google Translate API key which is used to generate translations (charge is applicable)

The command create-translations generates copies of the -source-language file, one per language specified in the -languages flag (seperated by comma).

$ i18n4go create-translations -v -f tmp/cli/i18n/app/en.all.json -source-language en -languages "en_US,fr_FR,es_ES,de_DE" -o tmp/cli/i18n/app/

i18n4go: creating translation files for: tmp/cli/i18n/app/en.all.json

i18n4go: creating translation file copy for language: en_US
i18n4go: creating translation file: tmp/cli/i18n/app/en_US.all.json
i18n4go: created default translation file: tmp/cli/i18n/app/en_US.all.json
i18n4go: creating translation file copy for language: fr_FR
i18n4go: creating translation file: tmp/cli/i18n/app/fr_FR.all.json
i18n4go: created default translation file: tmp/cli/i18n/app/fr_FR.all.json
i18n4go: creating translation file copy for language: es_ES
i18n4go: creating translation file: tmp/cli/i18n/app/es_ES.all.json
i18n4go: created default translation file: tmp/cli/i18n/app/es_ES.all.json
i18n4go: creating translation file copy for language: de_DE
i18n4go: creating translation file: tmp/cli/i18n/app/de_DE.all.json
i18n4go: created default translation file: tmp/cli/i18n/app/de_DE.all.json

Total time: 2.143251ms

Optionally, we can create automated translations for the generated copies using Google Translate[link] passing the google-translate-api-key flag.

verify-strings

The general usage for verify-strings command is:

  ...
  VERIFY-STRINGS:

  verify-strings             the verify strings command


  -f                         the source translation file

  --source-language          [optional] the source language of the source translation file (default to 'en')
  --languages                a comma separated list of valid languages with optional territory, e.g., "en, en_US, fr_FR, es"
  --language-files           a comma separated list of target files for different languages to compare, e.g., "en, en_US, fr_FR, es"
                             if not specified then the languages flag is used to find target files in same directory as source

The command verify-strings assures that combined language files have exactly the same keys.

For instance, in the example in merge-strings we created a combined language file called ./tmp/cli/i18n/app/en.all.json and if we also had a ./tmp/cli/i18n/app/fr.all.json for French and that file had missing strings then running the verify-strings would generate a tmp/cli/i18n/app/fr.all.json.missing.diff.json, as in the following:

$ i18n4go verify-strings -v -f tmp/cli/i18n/app/en.all.json -languages "fr"

targetFilenames: [tmp/cli/i18n/app/fr.all.json]
i18n4go: ERROR input file does not match target file: tmp/cli/i18n/app/fr.all.json
i18n4go: generated diff file: tmp/cli/i18n/app/fr.all.json.missing.diff.json
i18n4go: Error verifying target filename:  tmp/cli/i18n/app/fr.all.json
i18n4go: Could not verify strings for input filename, err: i18n4go: target file is missing i18n strings with IDs: --,'%v',-

Similarly, verify-strings will make sure that no additonal strings are added. So if we had an additional German de.all.json file that included additional strings running verify-strings would include a tmp/cli/i18n/app/de.all.json.extra.diff.json.

$ i18n4go verify-strings -v -f tmp/cli/i18n/app/en.all.json -languages "fr,de"

targetFilenames: [tmp/cli/i18n/app/fr.all.json tmp/cli/i18n/app/de.all.json]
i18n4go: ERROR input file does not match target file: tmp/cli/i18n/app/fr.all.json
i18n4go: generated diff file: tmp/cli/i18n/app/fr.all.json.missing.diff.json
i18n4go: Error verifying target filename:  tmp/cli/i18n/app/fr.all.json
i18n4go: WARNING target file has extra key with ID:  advanced
i18n4go: WARNING target file has extra key with ID:  apps
i18n4go: WARNING target file contains total of extra keys: 2
i18n4go: generated diff file: tmp/cli/i18n/app/de.all.json.extra.diff.json
i18n4go: Error verifying target filename:  tmp/cli/i18n/app/de.all.json
i18n4go: Could not verify strings for input filename, err: i18n4go: target file has extra i18n strings with IDs: advanced,apps

Finally, if a combined language file contains both extra and missing keys then verify-strings will generate two diff files: missing and extra.

checkup

The general usage for checkup command is:

  ...
  CHECKUP:

  checkup               the checkup command


  -q                    the qualifier to use when calling the T(...), defaults to empty but can be used to set to something like i18n for example, such that, i18n.T(...) is used for T(...) function

  --ignore-regexp       [optional] a perl-style regular expression for files to ignore, e.g., ".*test.*"

The checkup command ensures that the strings in code match strings in resource files and vice versa.

fixup

The general usage for fixup command is:

  ...
  FIXUP:

  -c fixup            the fixup command

The fixup command interactively lets users add, update, or remove translations keys from code and resource files.

Specifying `excluded.json` File

The exclude.json file can be used to manage which strings should not be extract with the extracting-strings command. In the excluded.json file, you can specifie string literals to ignore as well as classes of strings using a Perl-style regular expression. We have provided an example file exclude to demonstrate the string and regexp cases.

string literals

String literals are defined within the excludedStrings array. Any strings in your source files that exactly matches one of these will not be extracted to the generated files from extracted strings.

  ...
  "excludedStrings" : [
    "",
    " ",
    "\n",
    "help",
    ...
  ]
}

As an example run, generate an extracted string files useing the command:

$ i18n4go extract-strings -p -d ./tmp/cli/cf/app/ -o ./tmp/cli/i18n -output-match-package -ignore-regexp ".*test.*" -e ./example/excluded.json

If we inspect the ./tmp/cli/i18n/app/app.go.en.json file there should not be an entry for "id": "help", but you should still see an entry for "id": "show help"

regular expressions

Regular expressions can be defined using the same JSON annotation as string literals with the tag "excludedRegexps".

{
...
"excludedRegexps" : [
   "^\\w$",
   "^json:"
 ]
}

As an example for regular expressions, let us consider the ^json:. This expression will remove any string containg json: which would be useful when parsing the ./tmp/cli/cf/api/resources/events.go file such as: ExitDescription string json:"exit_description"`. After running the command:

$ i18n4go extract-strings -v -d ./tmp/cli/cf/api/resources -o ./tmp/cli/i18n -output-match-package -ignore-regexp ".*test.*" -e ./example/excluded.json

We can inspect the ./tmp/cli/i18n/resources/events.go.en.json file and see that there are no strings with the expression json:.

Troubleshooting / FAQs

None for now. Submit questions/comments as issues and we will update here

Filing Bugs

For simple bugs (eg: text formatting, help messages, etc), please provide

the command options you ran
what occurred
what you expected to occur

For panics and other crashes, please provide

the command you ran
the stack trace generated (if any)
any other relevant information

Cloning the repository

Install Go
Clone (Forking beforehand for development).
Ensure your $GOPATH is set correctly

Building

Run ./bin/build
The binary will be built into the ./out directory

Optionally, you can use bin/run to compile and run the executable in one step.

Developing

Run go get golang.org/x/tools/cmd/vet
Run go get github.com/xxx ... to install test dependencies (as you see errors)
Write a Ginkgo test
Run bin/test and watch the test fail
Make the test pass
Submit a pull request

Contributing

We gratefully acknowledge and thank the current contributors
We welcome any and all contributions as Pull Requests (PR)
We also welcome issues and bug report and new feature request. We will address as time permits
Follow the steps above in Developing to get your system setup correctly
Please make sure your PR is passing Travis before submitting
Feel free to email me or the current collaborators if you have additional questions about contributions
Before submitting your first PR, please read and follow steps in CONTRIBUTING.md

Managing dependencies

All dependencies managed via gvt

Short `gvt` Guide

If you ever import a new package foo/bar (after you go get foo/bar, so that foo/bar is in $GOPATH), you can type gvt get foo/bar to add it to the vendor directory.
If you ever remove a dependency or a link becomes deprecated, the easiest way is probably to remove your entire vendors/foo/bar directory
To update an existing dependency, you can use gvt update foo/bar

Current conventions

Basic Go conventions
Strict TDD for any code added or changed
Go fakes when needing to mock objects

(*) these items are in the works, we will remove the * once they are available

Name		Name	Last commit message	Last commit date
Latest commit History 553 Commits
.github		.github
bin		bin
docs		docs
examples		examples
i18n4go		i18n4go
integration		integration
slack		slack
test_fixtures		test_fixtures
.gitignore		.gitignore
.travis.yml		.travis.yml
CHANGELOG.md		CHANGELOG.md
CONTRIBUTING.md		CONTRIBUTING.md
LICENSE		LICENSE
README.md		README.md
go.mod		go.mod
go.sum		go.sum

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i18n Tooling for the Go Language

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verify-strings

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fixup

Specifying `excluded.json` File

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For simple bugs (eg: text formatting, help messages, etc), please provide

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i18n Tooling for the Go Language

Getting Started

Overview Presentations, Talks, Blogs

Getting Latest Executable: i18n4go

Cloning and Building

Running Tests

Typical Workflow

Typical Workflow Diagram

Help

extract-strings

merge-strings

rewrite-package

create-translations

verify-strings

checkup

fixup

Specifying excluded.json File

string literals

regular expressions

Troubleshooting / FAQs

Filing Bugs

For simple bugs (eg: text formatting, help messages, etc), please provide

For panics and other crashes, please provide

Cloning the repository

Building

Developing

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Managing dependencies

Short gvt Guide

Current conventions

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Languages

Specifying `excluded.json` File

Short `gvt` Guide

Packages