sap-jenkins-library/DEVELOPMENT.md

Development

Table of contents:

1. Getting started
2. Build the project
3. Generating step framework
4. Best practices for writing piper-go steps
5. Testing
6. Debugging
7. Release

Getting started

1. Ramp up your development environment
2. Get familiar with Go language
3. Create a GitHub account
4. Setup GitHub access via SSH
5. Create and checkout a repo fork
6. Optional: Get Jenkins related environment
7. Optional: Get familiar with Jenkins Pipelines as Code

Ramp up

First you need to set up an appropriate development environment:

1. Install Go, see GO Getting Started
2. Install an IDE with Go plugins, see for example Go in Visual Studio Code

Go basics

In order to get yourself started, there is a lot of useful information out there.

As a first step to take we highly recommend the Golang documentation, especially A Tour of Go.

We have a strong focus on high quality software and contributions without adequate tests will not be accepted. There is an excellent resource which teaches Go using a test-driven approach: Learn Go with Tests

Checkout your fork

The project uses Go modules. Thus please make sure to NOT checkout the project into your GOPATH.

To check out this repository:

1. Create your own fork of this repo
2. Clone it to your machine, for example like:

mkdir -p ${HOME}/projects/jenkins-library
cd ${HOME}/projects
git clone git@github.com:${YOUR_GITHUB_USERNAME}/jenkins-library.git
cd jenkins-library
git remote add upstream git@github.com:sap/jenkins-library.git
git remote set-url --push upstream no_push

Jenkins environment

If you want to contribute also to the Jenkins-specific parts like

• Jenkins library step
• Jenkins pipeline integration

you need to do the following in addition:

• Install Groovy
• Install Maven
• Get a local Jenkins installed: Use for example cx-server

Jenkins pipelines

The Jenkins related parts depend on

• Jenkins Pipelines as Code
• Jenkins Shared Libraries

You should get familiar with these concepts for contributing to the Jenkins-specific parts.

Build the project

Build the executable suitable for the CI/CD Linux target environments

Use Docker:

docker build -t piper:latest .

You can extract the binary using Docker means to your local filesystem:

docker create --name piper piper:latest
docker cp piper:/piper .
docker rm piper

Generating step framework

The steps are generated based on the yaml files in resources/metadata/ with the following command go run pkg/generator/step-metadata.go.

The yaml format is kept pretty close to Tekton's task format. Where the Tekton format was not sufficient some extenstions have been made.

Examples are:

• matadata - longDescription
• spec - inputs - secrets
• spec - containers
• spec - sidecars

There are certain extensions:

• aliases allow alternative parameter names also supporting deeper configuration structures. Example

• resources allow to read for example from a shared commonPipelineEnvironment which contains information which has been provided by a previous step in the pipeline via an output. Example

• secrets allow to specify references to Jenkins credentials which can be used in the groovy library. Example

• outputs allow to write to dedicated outputs like

  • Influx metrics. Example
  • Sharing data via commonPipelineEnvironment which can be used by another step as input

• conditions allow for example to specify in which case a certain container is used (depending on a configuration parameter). Example

Best practices for writing piper-go steps

1. Logging
2. Error handling

Implementing a new step starts by adding a new yaml file in resources/metadata/ and running the step generator. This creates most of the boiler-plate code for the step's implementation in cmd/. There are four files per step based on the name given within the yaml:

1. cmd/<step>.go - contains the skeleton of your step implementation.
2. cmd/<step>_test.go - write your unit tests here.
3. cmd/<step>_generated.go - contains the generated boiler plate code, and a dedicated type definition for your step's options.
4. cmd/<step>_generated_test.go - contains a simple unit test for the generated part.

You never edit in the generated parts. If you need to make changes, you make them in the yaml and re-run the step generator (which will of course not overwrite your implementation).

The file cmd/<step>.go initially contains two functions:

func step(options stepOptions, telemetryData *telemetry.CustomData) {
    err := runStep(&options, telemetryData)
    if err != nil {
        log.Entry().WithError(err).Fatal("step execution failed")
    }
}

func runStep(options *stepOptions, telemetryData *telemetry.CustomData) error {
}

The separation into these two functions facilitates unit tests and mocking. From your tests, you could call runStep() with mocking instances of needed objects, while inside step(), you create runtime instances of these objects.

Logging

Logging is done via the sirupsen/logrus framework. It can conveniently be accessed through:

import (
    "github.com/SAP/jenkins-library/pkg/log"
)

func myStep ...
    ...
    log.Entry().Info("This is my info.")
    ...
}

If a fatal error occurs your code should act similar to:

    ...
    if err != nil {
        log.Entry().
            WithError(err).
            Fatal("failed to execute step ...")
    }

Calling Fatal results in an os.Exit(0) and before exiting some cleanup actions (e.g. writing output data, writing telemetry data if not deactivated by the user, ...) are performed.

Error handling

In order to better understand the root cause of errors that occur, we wrap errors like

    f, err := os.Open(path)
    if err != nil {
        return errors.Wrapf(err, "open failed for %v", path)
    }
    defer f.Close()

We use github.com/pkg/errors for that.

It has proven a good practice to bubble up errors until the runtime entry function and only there exit via the logging framework (see also logging).

Testing

1. Mocking
2. Mockable Interface
3. Global function pointers

Unit tests are done using basic golang means.

Additionally, we encourage you to use github.com/stretchr/testify/assert in order to have slimmer assertions if you like. A good pattern to follow is this:

func TestNameOfFunctionUnderTest(t *testing.T) {
    t.Run("A description of the test case", func(t *testing.T) {
        // init
        // test
        // assert
    })
    t.Run("Another test case", func(t *testing.T) {
        // init
        // test
        // assert
    })
}

This will also structure the test output for better readability.

Mocking

Tests should be written only for the code of your step implementation, while any external functionality should be mocked, in order to test all code paths including the error cases.

There are (at least) two approaches for this:

Mockable Interface

In this approach you declare an interface that contains every external function used within your step that you need to be able to mock. In addition, you declare a struct which holds the data you need during runtime, and implement the interface with the "real" functions. Here is an example to illustrate:

import (
    "github.com/SAP/jenkins-library/pkg/piperutils"
)

type myStepUtils interface {
    fileExists(path string) (bool, error)
    fileRead(path string) ([]byte, error)
}

type myUtilsData struct {
    fileUtils piperutils.Files
}

func (u *myUtilsData) fileExists(path string) (bool, error) {
    return u.fileUtils.FileExists(path)
}

func (u *myUtilsData) fileRead(path string) ([]byte, error) {
    return u.fileUtils.FileRead(path)
}

Then you create the runtime version of the utils data in your top-level entry function and pass it to your run*() function:

func step(options stepOptions, _ *telemetry.CustomData) {
    utils := myUtilsData{
        fileUtils: piperutils.Files{},
    }
    err := runStep(&options, &utils)
    ...
}

func runStep(options *stepOptions, utils myStepUtils) error {
    ...
    exists, err := utils.fileExists(path)
    ...
}

In your tests, you would provide a mocking implementation of this interface and pass instances of that to the functions under test. To better illustrate this, here is an example for the interface above implemented in the <step>_test.go file:

type mockUtilsBundle struct {
    files map[string][]byte
}

func newMockUtilsBundle() mockUtilsBundle {
    utils := mockUtilsBundle{}
    utils.files = map[string][]byte{}
    return utils
}

func (m *mockUtilsBundle) fileExists(path string) (bool, error) {
    content := m.files[path]
    return content != nil, nil
}

func (m *mockUtilsBundle) fileRead(path string) ([]byte, error) {
    content := m.files[path]
    if content == nil {
        return nil, fmt.Errorf("could not read '%s': %w", path, os.ErrNotExist)
    }
    return content, nil
}

// This is how it would be used in tests:

func TestSomeFunction() {
    t.Run("Happy path", func(t *testing.T) {
        // init
        utils := newMockUtilsBundle()
        utils.files["some/path/file.xml"] = []byte(´content of the file´)
        // test
        err := someFunction(&utils)
        // assert
        assert.NoError(t, err)
    })
    t.Run("Error path", func(t *testing.T) {
        // init
        utils := newMockUtilsBundle()
        // test
        err := someFunction(&utils)
        // assert
        assert.EqualError(t, err, "could not read 'some/path/file.xml'")
    })
}

Global Function Pointers

An alternative approach are global function pointers:

import (
    FileUtils "github.com/SAP/jenkins-library/pkg/piperutils"
)

var fileUtilsExists = FileUtils.FileExists

func someFunction(options *stepOptions) error {
    ...
    exists, err := fileUtilsExists(path)
    ...
}

In your tests, you can then simply set the function pointer to a mocking implementation:

func TestSomeFunction() {
    t.Run("Happy path", func(t *testing.T) {
        // init
        originalFileExists := fileUtilsExists
        fileUtilsExists = func(filename string) (bool, error) {
            return true, nil
        }
        defer fileUtilsExists = originalFileExists
        // test
        err := someFunction(...)
        // assert
        assert.NoError(t, err)
    })
    t.Run("Error path", func(t *testing.T) {
        // init
        originalFileExists := fileUtilsExists
        fileUtilsExists = func(filename string) (bool, error) {
            return false, errors.New("something happened")
        }
        defer fileUtilsExists = originalFileExists
        // test
        err := someFunction(...)
        // assert
        assert.EqualError(t, err, "something happened")
    })
}

Both approaches have their own benefits. Global function pointers require less preparation in the actual implementation and give great flexibility in the tests, while mocking interfaces tend to result in more code re-use and slim down the tests. The mocking implementation of a utils interface can facilitate implementations of related functions to be based on shared data.

Debugging

Debugging can be initiated with VS code fairly easily. Compile the binary with specific compiler flags to turn off optimizations go build -gcflags "all=-N -l" -o piper.exe.

Modify the launch.json located in folder .vscode of your project root to point with program exactly to the binary that you just built with above command - must be an absolute path. Add any arguments required for the execution of the Piper step to args. What is separated with a blank on the command line must go into a separate string.

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Launch",
            "type": "go",
            "request": "launch",
            "mode": "exec",
            "program": "C:/CF@HCP/git/jenkins-library-public/piper.exe",
            "env": {},
            "args": ["checkmarxExecuteScan", "--password", "abcd", "--username", "1234", "--projectName", "testProject4711", "--serverUrl", "https://cx.server.com/"]
        }
    ]
}

Finally, set your breakpoints and use the Launch button in the VS code UI to start debugging.

Release

Releases are performed using Project "Piper" Action. We release on schedule (once a week) and on demand. To perform a release, the respective action must be invoked for which a convenience script is available in contrib/perform-release.sh. It requires a personal access token for GitHub with repo scope. Example usage PIPER_RELEASE_TOKEN=THIS_IS_MY_TOKEN contrib/perform-release.sh.