Missing Semester 08 - Metaprogramming

Metaprogramming is processes that surround the work that you do when working with software: how your system is built, how it's tested and how you add dependencies to it.

Written by Eva Dee on (about a 3 minute read).

Build systems

  • Build system: a tool that can help you with the build process (like npm)
  • Build process: some sequence of operations you need to do to go from your inputs to your outputs.

make

The make utility requires a Makefile which defines a set of tasks to be executed.

You may have used make to compile a program from source code.

Most open-source projects use make to compile a final executable binary, which can then be installed using make install.

Create a makefile:

say_hello:
        echo "Hello World"

And then run it:

$ make
echo "Hello World"
Hello World

Tabs are important!

target: prerequisites
<TAB> recipe

Semantic versioning

With semantic versioning, every version number is of the form: major.minor.patch:

  • If a new release does not change the API, increase the patch version. (security fixes)
  • If you add to your API in a backward-compatible way, increase the minor version.
  • If you change the API in a non-backward-compatible way, increase the major version.

Lock files

  • Lock file: a file that lists the exact version you currently depen on for each dependency.

  • Vendoring - a.k.a. dependency locking: when you copy all the code of your dependencies into your own project.

Continuous integration (CI)

Continuous integration, or CI, is an umbrella term for “stuff that runs whenever your code changes” - a.k.a. event-triggered actions. E.g CIs: Travis CI, Azure Pipelines, and GitHub Actions.

They all work in roughly the same way: you add a file to your repository that describes what should happen when various things happen to that repository (e.g. re-run the tests when there are code changes.

Dependabot: checks whether your dependencies are up-to-date and submits an automatic PR if they're not.

The badges in GitHub come from the CI as well: e.g test coverage, dependencies, documentaton versioning.

GitHub pages is a type of a CI action - it builds a blog from your markdown files (using Jeykll).

Testing

  • Test suite: all of the tests in the program
  • Unit test: tests a single feature
  • Integration test: test the interaction between different subsystems of the program
  • Regression test: tests things that were broken in the past. They prevent your projects from regressing to earlier bugs.
  • Mocking: being able to replace the parts of your system with a dummy version of itself.