133 lines
4.9 KiB
Markdown
133 lines
4.9 KiB
Markdown
# `protoc-gen-gotemplate`
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:open_file_folder: protocol generator + golang text/template (protobuf)
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A generic **code**/script/data generator based on [Protobuf](https://developers.google.com/protocol-buffers/).
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---
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This project is a generator plugin for the Google Protocol Buffers compiler (`protoc`).
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The plugin parses **protobuf** files, generates an **ast**, and walks a local **templates directory** to generate files using the [Golang's `text/template` engine](https://golang.org/pkg/text/template/).
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## Philosophy
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* protobuf-first
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* no built-in template, only user defined templates
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* kiss, *keep it stupid simple*
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## Under the hood
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1. the *user* `protobuf` files are parsed by [`protoc`](https://github.com/google/protobuf/releases)
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2. the `ast` is generated by [`protoc-gen-go` helpers](https://github.com/golang/protobuf/tree/master/protoc-gen-go)
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3. the `ast` is given to [Golang's `text/template` engine](https://golang.org/pkg/text/template/) for each *user* template files
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4. the *funcmap* enriching the template engine is based on [Masterminds/sprig](https://github.com/Masterminds/sprig), and contains type-manipulation, iteration and language-specific helpers
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## Web editor
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[Demo server](http://protoc-gen-gotemplate.m.42.am/)
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## Usage
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`protoc-gen-gotemplate` requires a **template_dir** directory *(by default `./templates`)*.
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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.
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---
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```console
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$> ls -R
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input.proto templates/doc.txt.tmpl templates/config.json.tmpl
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$> protoc --gotemplate_out=. input.proto
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$> ls -R
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input.proto templates/doc.txt.tmpl templates/config.json.tmpl
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doc.txt config.json
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```
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### Options
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You can specify custom options, as follow:
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```console
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$> protoc --gotemplate_out=debug=true,template_dir=/path/to/template/directory:. input.proto
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```
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| Option | Default Value | Accepted Values | Description
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|-----------------------|---------------|---------------------------|-----------------------
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| `template_dir` | `./template` | absolute or relative path | path to look for templates
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| `destination_dir` | `.` | absolute or relative path | base path to write output
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| `single-package-mode` | *false* | `true` or `false` | if *true*, `protoc` won't accept multiple packages to be compiled at once (*!= from `all`*), but will support `Message` lookup across the imported protobuf dependencies
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| `debug` | *false* | `true` or `false` | if *true*, `protoc` will generate a more verbose output
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| `all` | *false* | `true` or `false` | if *true*, protobuf files without `Service` will also be parsed
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##### Hints
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Shipping the templates with your project is very smart and useful when contributing on git-based projects.
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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, ...)
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See [examples](./examples).
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## Funcmap
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This project uses [Masterminds/sprig](https://github.com/Masterminds/sprig) library and additional functions to extend the builtin [text/template](https://golang.org/pkg/text/template) helpers.
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Non-exhaustive list of new helpers:s
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* **all the functions from [sprig](https://github.com/Masterminds/sprig)**
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* `json`
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* `prettyjson`
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* `first`
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* `last`
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* `splitArray`
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* `upperFirst`
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* `lowerFirst`
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* `camelCase`
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* `lowerCamelCase`
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* `kebabCase`
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* `snakeCase`
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* `getProtoFile`
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* `getMessageType`
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* `getEnumValue`
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* `isFieldMessage`
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* `isFieldRepeated`
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* `goType`
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* `goTypeWithPackage`
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* `jsType`
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* `jsSuffixReserved`
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* `namespacedFlowType`
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* `httpVerb`
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* `httpPath`
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* `shortType`
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* `urlHasVarsFromMessage`
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See the project helpers for the complete list.
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## Install
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* Install the **Go** compiler and tools from https://golang.org/doc/install
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* Install **protobuf**: `go get -u github.com/golang/protobuf/{proto,protoc-gen-go}`
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* Install **protoc-gen-gotemplate**: `go get -u github.com/moul/protoc-gen-gotemplate`
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## Docker
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* automated docker hub build: [https://hub.docker.com/r/moul/protoc-gen-gotemplate/](https://hub.docker.com/r/moul/protoc-gen-gotemplate/)
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* Based on [http://github.com/znly/protoc](http://github.com/znly/protoc)
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Usage:
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```console
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$> docker run --rm -v "$(pwd):$(pwd)" -w "$(pwd)" moul/protoc-gen-gotemplate -I. --gotemplate_out=./output/ ./*.proto
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```
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## Projects using `protoc-gen-gotemplate`
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* [kafka-gateway](https://github.com/moul/kafka-gateway/): Kafka gateway/proxy (gRPC + http) using Go-Kit
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* [translator](https://github.com/moul/translator): Translator Micro-service using Gettext and Go-Kit
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* [acl](https://github.com/moul/acl): ACL micro-service (gRPC/protobuf + http/json)
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## License
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MIT
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