There are two primary ways to help:
- Using the issue tracker, and
- Changing the code-base.
Use the issue tracker to suggest feature requests, report bugs, and ask questions. This is also a great way to connect with the developers of the project as well as others who are interested in this solution.
Use the issue tracker to find ways to contribute. Find a bug or a feature, mention in the issue that you will take on that effort, then follow the "Changing the code-base" guidance below.
Generally speaking, you should fork this repository, make changes in your own fork, and then submit a pull-request. All new code should have been thoroughly tested end-to-end in order to validate implemented features and the presence or lack of defects.
- Configure this repository as a remote for your own fork, and
- Sync your fork with this repository before beginning to work on a new pull-request.
All pipeline library coding must come with automated unit tests.
The contract of functionality exposed by a library functionality needs to be documented, so it can be properly used. Implementation of a functionality and its documentation shall happen within the same commit(s).
Pipeline steps must not make use of return values. The pattern for sharing parameters between pipeline steps or between a pipeline step and a pipeline script is sharing values via the commonPipelineEnvironment. Since there is no return value from a pipeline step the return value of a pipeline step is already void rather than def.
The code should follow any stylistic and architectural guidelines prescribed by the project. In the absence of guidelines, mimic the styles and patterns in the existing code-base.
Variables, methods, types and so on shall have meaningful self describing names. Doing so makes understanding code easier and requires less commenting. It helps people who did not write the code to understand it better.
Code shall contain comments to explain the intention of the code when it is unclear what the intention of the author was. In such cases, comments should describe the "why" and not the "what" (that is in the code already).
To ensure a common file format, there is a .editorConfig file in place. To respect this file, check if your editor does support it natively or you need to download a plugin.
Write meaningful commit messages and adhere to standard formatting.
Good commit messages speed up the review process and help to keep this project maintainable in the long term.
The intention of this section is to describe the code style for this project. As reference document, the Groovy's style guide was taken. For further reading about Groovy's syntax and examples, please refer to this guide.
This project is intended to run in Jenkins [2] as part of a Jenkins Pipeline [3]. It is composed by Jenkins Pipeline's syntax, Groovy's syntax and Java's syntax.
Some Groovy's syntax is not yet supported by Jenkins. It is also the intention of this section to remark which Groovy's syntax is not yet supported by Jenkins.
As Groovy supports 99% of Java’s syntax [1], many Java developers tend to write Groovy code using Java's syntax. Such a developer should also consider the following code style for this project.
In Groovy it is optional to use the return keyword. Use explicitly the return keyword for better readability.
When using def in Groovy, the type is Object. Using def simplifies the code, for example imports are not needed, and therefore the development is faster.
By default, classes and methods are public, the use of the public modifier is not needed.
In Groovy is possible to omit parentheses for top-level expressions, but Jenkins Pipeline's syntax use a block, specifically pipeline { } as top-level expression [4]. Do not omit parenthesis for Groovy methods because Jenkins will interpret the method as a Pipeline Step. Conversely, do omit parenthesis for Jenkins Pipeline's Steps.
In Groovy, the .class suffix is not needed. Omit the .class suffix for simplicity and better readability.
e.g. new ExpectedException().expect(AbortException.class)
--> new ExpectedException().expect(AbortException)
When declaring a field without modifier inside a Groovy bean, the Groovy compiler generates a private field and a getter and setter.
Do not initialize beans with named parameters, because it is not supported by Jenkins:
e.g. Version javaVersion = new Version( major: 1, minor: 8)
Initialize beans using Java syntax:
e.g. Version javaVersion = new Version(1, 8)
Use named parameters for Jenkins Pipeline Steps:
e.g. sh returnStdout: true, script: command
The with operator is not yet supported by Jenkins, and it must not be used or encapsulated in a @NonCPS method.
Use Groovy’s == instead of Java equals() to avoid NullPointerExceptions. To compare the references of objects, instead of ==, you should use a.is(b) [1].
In Groovy, single quotes create Java Strings, and double quotes can create Java Strings or GStrings, depending if there is or not interpolation of variables [1]. Using GStrings variable and string concatenation is more simple.
For variables, or variable.property, drop the curly braces:
e.g. echo "[INFO] ${name} version ${version.version} is installed."
--> echo "[INFO] $name version $version.version is installed."
This notation avoids to double escape backslashes, making easier working with regex.
Use the native syntax for data structures provided by Groovy like lists, maps, regex, or ranges of values.
Use the additional methods provided by Groovy to manipulate String, Files, Streams, Collections, and other classes. For a complete description of all available methods, please read the GDK API [5].
Groovy’s switch accepts any kind of type, thereby is more powerful. In this case, the use of def instead of a type is necessary.
In Groovy, it is possible to assign an alias to imported packages. Use alias for imported packages to avoid the use of fully-qualified names and increase readability.
In Groovy a null, void, equal to zero, or empty object evaluates to false, and if not, evaluates to true. Instead of writing null and size checks e.g. if (name != null && name.length > 0) {}, use just the object if (name) {}.
Use the safe dereference operator ?., to simplify the code for accessing objects and object members safely. Using this operator, the Groovy compiler checks null objects and null object members, and returns null if the object or the object member is null and never throws a NullPointerException.
Use Elvis operator ?: to simplify default value validations.
If the type of the exception thrown inside a try block is not important, catch any exception using the any keyword.
To check parameters, return values, and more, use the assert statement.
[1] Groovy's syntax: http://groovy-lang.org/style-guide.html
[2] Jenkins: https://jenkins.io/doc/book/getting-started/
[3] Jenkins Pipeline: https://jenkins.io/doc/book/pipeline/
[4] Jenkins Pipeline's syntax: https://jenkins.io/doc/book/pipeline/syntax/
[5] GDK: Groovy Development Kit: http://groovy-lang.org/groovy-dev-kit.html