Git Pre-commit

W hether you are doing Software development or writing Infrastructure code in a team, it is of utmost importance to define some standards for the codebase. There are plenty of plugins for code linting, formatting and much more integrated with IDEs such as VSCode, JetBrains etc. But the problem is that everyone has their own IDE setup. For example, some developers add config to "delete trailing spaces", while others do not. Secondly, not every developer uses the same IDE. In order to eliminate such problems, Git pre-commit hooks can be useful. Even though people on the Internet have different opinions, I am going to list some benefits of it.

Allows developers to see and fix their code almost instantly.
It keeps the codebase clean and standardized independently of the IDE being used.
Besides linting, it also performs secret checks and many other things…

However, using it intensively could disrupt the developer’s workflow. It can shift their focus from bug fixing and adding new features to linting.

In this blog post, I will walk you through, how we can add pre-commit hooks to our IaC codebase.

Install pre-commit

Since pre-commit written in python you need to install the pre-commit module.

pip install pre-commit

Add a pre-commit Configuration

create .pre-commit-config.yaml file. For demonstration purposes, I will add some basic hooks such as check-yaml, end-of-file-fixer, trailing-whitespace and terraform_fmt hook to format terraform files.

repos:
- repo: https://github.com/pre-commit/pre-commit-hooks
  rev: v6.0.0
  hooks:
  -   id: check-yaml
  -   id: end-of-file-fixer
  -   id: trailing-whitespace
- repo: https://github.com/antonbabenko/pre-commit-terraform
  rev: v1.103.0
  hooks:
  - id: terraform_fmt

After add the configuration file, next step to instruct pre-commit to install the hooks.

pre-commit install
pre-commit installed at .git/hooks/pre-commit

Using pre-commit

In this example, variables.tf file generated and some variables are defined. Of course without any linting.

pre-commit run
check yaml...........................................(no files to check)Skipped
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
Terraform fmt............................................................Failed
- hook id: terraform_fmt
- files were modified by this hook

variables.tf

As you see above, the terraform_fmt hook has failed because the file is not formatted well. At first run it failed but plugin has fixed the file.

index 6b70073..3f21cc1 100644
--- a/terraform/variables.tf
+++ b/terraform/variables.tf
@@ -1,5 +1,5 @@
 variable "environment" {
-  type          = string
+  type = string
 }

We can now add it to the staging area and run the pre-commit again.

pre-commit run
check yaml...........................................(no files to check)Skipped
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
Terraform fmt............................................................Passed

At this time no issue detected. By the way, you can also run pre-commit for all files in the repository.

pre-commit run --all-files

Tip:

You can still bypass the hooks.

git commit -m "I will fix it next time" --no-verify

For more information you can check following urls about the pre-commit.

https://git-scm.com/book/ms/v2/Customizing-Git-Git-Hooks
https://pre-commit.com/
https://github.com/antonbabenko/pre-commit-terraform

Git Pre-commit

Install pre-commit

Add a pre-commit Configuration

Using pre-commit

Tip:

yilgo

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