protoc-gen-gotemplate

📂 protocol generator + golang text/template (protobuf)

A generic code/script/data generator based on Protobuf.

This project is a generator plugin for the Google Protocol Buffers compiler (protoc).

The plugin parses protobuf files, generates an ast, and walks a local templates directory to generate files using the Golang's text/template engine.

Philosophy

• protobuf-first
• no built-in template, only user defined templates
• kiss, keep it stupid simple

Under the hood

1. the user protobuf files are parsed by protoc
2. the ast is generated by protoc-gen-go helpers
3. the ast is given to Golang's text/template engine for each user template files
4. the funcmap enriching the template engine is based on Masterminds/sprig, and contains type-manipulation, iteration and language-specific helpers

Dev helpers

1. Pre-commit script for install: https://pre-commit.com

Web editor

Demo server

Usage

protoc-gen-gotemplate requires a template_dir directory (by default ./templates).

Every file ending with .tmpl will be processed and written to the destination folder, following the file hierarchy of the template_dir, and remove the .tmpl extension.

$> ls -R
input.proto     templates/doc.txt.tmpl      templates/config.json.tmpl
$> protoc --gotemplate_out=. input.proto
$> ls -R
input.proto     templates/doc.txt.tmpl      templates/config.json.tmpl
doc.txt         config.json

Options

You can specify custom options, as follow:

$> protoc --gotemplate_out=debug=true,template_dir=/path/to/template/directory:. input.proto

Hints

Shipping the templates with your project is very smart and useful when contributing on git-based projects.

Another workflow consists in having a dedicated repository for generic templates which is then versioned and vendored with multiple projects (npm package, golang vendor package, ...)

See examples.

Funcmap

This project uses Masterminds/sprig library and additional functions to extend the builtin text/template helpers.

Non-exhaustive list of new helpers:

• all the functions from sprig
• add
• boolFieldExtension
• camelCase
• contains
• divide
• fieldMapKeyType
• fieldMapValueType
• first
• getEnumValue
• getMessageType
• getProtoFile
• goNormalize
• goTypeWithPackage
• goType
• goZeroValue
• haskellType
• httpBody
• httpPath
• httpPathsAdditionalBindings
• httpVerb
• index
• int64FieldExtension
• isFieldMap
• isFieldMessageTimeStamp
• isFieldMessage
• isFieldRepeated
• jsSuffixReserved
• jsType
• json
• kebabCase
• last
• leadingComment
• leadingDetachedComments
• lowerCamelCase
• lowerFirst
• lowerGoNormalize
• multiply
• namespacedFlowType
• prettyjson
• replaceDict
• shortType
• snakeCase
• splitArray
• stringFieldExtension
• stringMethodOptionsExtension
• string
• subtract
• trailingComment
• trimstr
• upperFirst
• urlHasVarsFromMessage

See the project helpers for the complete list.

Install

• Install the Go compiler and tools from https://golang.org/doc/install
• Install protobuf: go install github.com/golang/protobuf/protoc-gen-go@latest
• Install protoc-gen-gotemplate: go install moul.io/protoc-gen-gotemplate@latest

Docker

• automated docker hub build: https://hub.docker.com/r/moul/protoc-gen-gotemplate/
• Based on http://github.com/znly/protoc

Usage:

$> docker run --rm -v "$(pwd):$(pwd)" -w "$(pwd)" moul/protoc-gen-gotemplate -I. --gotemplate_out=./output/ ./*.proto

Projects using protoc-gen-gotemplate

• kafka-gateway: Kafka gateway/proxy (gRPC + http) using Go-Kit
• translator: Translator Micro-service using Gettext and Go-Kit
• acl: ACL micro-service (gRPC/protobuf + http/json)

See also

• pbhbs: protobuf gen based on handlebarjs template

License

MIT