Pact Plugin Template

Template project to help bootstrap a new Pact Plugin for the Pact framework.

Features:

• Stubbed gRPC methods ready to implement
• Automated release procedure
• Support for recommended common platform/targets
• Levelled logging for observability

TODO

• Support Matchers and Generators (requires FFI package support)

Repository Structure

├── go.mod            # Go module                              (✅ fill me in!)
├── main.go           # Entrypoint for the application
├── plugin.go         # Stub gRPC methods for you to implement (✅ fill me in!)
├── configuration.go  # Type definitions for your plugin's DSL (✅ fill me in!)
├── Makefile          # Build configuration                    (✅ fill me in!)
├── io_pact_plugin/   # Location of protobuf and gRPC definitions for Plugin Framework
├── log.go            # Logging utility
├── pact-plugin.json  # Plugin configuration file
├── pact.go           # Pact type definitions
├── server.go         # The gRPC server implementation
├── RELEASING.md      # Instructions on how to release 🚀

Developing the plugin

Prerequsites

The protoc compiler must be installed for this plugin

Create your new repository

1. Clone this repository
2. Create a new repository in GitHub. The name of the plugin should be pact-<PROJECT>-plugin e.g. pact-protobuf-plugin
3. Push this code to your new repository

Update the Go module name

Replace github.com/pact-foundation/pact-plugin-template-golang in go.mod with your github URL (without the protocol prefix) to identify the package uniquely.

Similarly, correct the import at the top of plugin.go and server.go.

Or simply do a workspace wide search and replace from github.com/pact-foundation/pact-plugin-template-golang to your go module name.

Run:

go mod tidy
go mod vendor

To ensure the dependencies and vendoring are correct.

Set the name and version

In the top of the Makefile set PROJECT to your plugin's name.

PROJECT should map to <PROJECT> in your GitHub repository.

NOTE: It's important that the name of your go module and the PROJECT variable must align, to create artifacts discoverable to the CLI tooling, such as the Plugin CLI.

Design the consumer interface

This is how the users of your plugin will write the plugin specific interaction details.

For example, take the following HTTP interaction:

await pact
  .addInteraction()
  .given('the Matt protocol exists')
  .uponReceiving('an HTTP request to /matt')
  .usingPlugin({
    plugin: 'matt',
    version: '0.0.4',
  })
  .withRequest('POST', '/matt', (builder) => {
    builder.pluginContents('application/matt', mattRequest); // <- request
  })
  .willRespondWith(200, (builder) => {
    builder.pluginContents('application/matt', mattResponse); // <- response
  })
  .executeTest((mockserver) => {
          ...

The user needs to specify the request and response body portion of the request.

Because the use cases for plugins are so wide and varied, the framework does not impose limits on this data structure and is something you need to design.

This being said, most plugins have opted to use a JSON structure.

This structure should be represented in configuration.go

Think about how you would like your user to specify the interaction details for the various interaction types.

Here is an example for a TCP plugin with a custom text protocol:

Synchronous Messages

Set the expected response from the API:

mattMessage := `{"response": {"body": "hellotcp"}}`

Asynchronous Messages

Set the request/response all in one go:

mattMessage := `{"request": {"body": "hellotcp"}, "response":{"body":"tcpworld"}}`

HTTP

Separate out the body on the request/response part of the interaction:

mattRequest := `{"request": {"body": "hello"}}`
mattResponse := `{"response":{"body":"world"}}`

Write the Plugin!

Implement the relevant RPC functions

Open plugin.go and update the relevant RPC functions.

Depending on your use case, some of the RPC calls won't be required, each method is well signposted to help you along.

Logging

You should log regularly. Debugging gRPC calls from the framework can be challenging, as the plugin is started asynchronously by the Plugin Driver behind the scenes.

There are two ways to log:

1. Stdout - all stdout (e.g. fmt.Print*) is pulled into the general Pact logs for the framework you're running
2. To file. All calls to log.Print* will be written to file

The log setup has three main features:

1. It works with the native Go log package
2. It logs to a file relative to plugin execution in log/plugin.log
3. It is levelled, at the direction of the plugin driver (that is, the log level will pass in from the driver which will restrict the levels logged in this plugin)

To write something to the log file, you simply use the log package, with the level prefixed as per below:

log.Println("[TRACE] ...")
log.Println("[DEBUG] ...")
log.Println("[INFO] ...")
log.Println("[WARN] ...")
log.Println("[ERROR] ...")

Publish your plugin

Follow the steps in Releasing to publish a new version of your Plugin.

Local Development

The following command will build the plugin, and install into the correct plugin directory for local development:

make install_local

You can then reference your plugin in local tests to try it out.

Regenerating the plugin protobuf definitions

If a new protobuf definition is required (e.g. to support a new feature), copy into the io_pact_plugin folder and run the following Make task:

make proto

It will update the definitions in the io_pact_plugin package. Note this may result in a breaking change, depending on the version. So upgrade carefully.

Supported targets

This code base should automatically create artifacts for the following OS/Architecture combiations:

OS	Architecture	Supported
OSX	x86_64	✅
OSX	arm	✅
Linux	x86_64	✅
Linux	arm	✅
Windows	x86_64	✅
Windows	arm	✅