docker-mailserver/docs/content/contributing/coding-style.md

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---
title: 'Contributing | Coding Style'
---
## Bash and Shell
When refactoring, writing or altering scripts, that is Shell and bash scripts, in any way, adhere to these rules:
1. **Adjust your style of coding to the style that is already present**! Even if you do not like it, this is due to consistency. There was a lot of work involved in making all scripts consistent.
2. **Use `shellcheck` to check your scripts**! Your contributions are checked by GitHub Actions too, so you will need to do this. You can **lint your work with `make lint`** to check against all targets.
3. **Use the provided `.editorconfig`** file.
4. Use `/bin/bash` instead of `/bin/sh`. Adjust the style accordingly.
5. `setup.sh` provides a good starting point to look for.
6. When appropriate, use the `set` builtin. We recommend `set -euEo pipefail` or `set -uE`.
## Styling rules
### If-Else-Statements
```bash
# when using braces, use double braces
# remember you do not need "" when using [[ ]]
if [[ <CONDITION1> ]] && [[ -f ${FILE} ]]
then
<CODE TO RUN>
# when running commands, you don't need braces
elif <COMMAND TO RUN>
<CODE TO TUN>
else
<CODE TO TUN>
fi
# equality checks with numbers are done
# with -eq/-ne/-lt/-ge, not != or ==
if [[ ${VAR} -ne 42 ]] || [[ ${SOME_VAR} -eq 6 ]]
then
<CODE TO RUN>
fi
```
### Variables & Braces
!!! attention
Variables are always uppercase. We always use braces.
If you forgot this and want to change it later, you can use [this link][regex]. The used regex is `\$([^{("\\'\/])([a-zA-Z0-9_]*)([^}\/ \t'"\n.\]:(=\\-]*)`, where you should in practice be able to replace all variable occurrences without braces with occurrences with braces.
```bash
# good
local VAR="good"
local NEW="${VAR}"
# bad -> CI will fail
var="bad"
new=$var
```
### Loops
Like `if-else`, loops look like this
```bash
for / while <LOOP CONDITION>
do
<CODE TO RUN>
done
```
### Functions
It's always nice to see the use of functions as it also provides a clear structure. If scripts are small, this is unnecessary, but if they become larger, please consider using functions. When doing so, provide `function _main`.
```bash
function _<name_underscored_and_lowercase>
{
<CODE TO RUN>
# variables that can be local should be local
local <LOCAL_VARIABLE_NAME>
}
```
### Error Tracing
A construct to trace error in your scripts looks like this. Remember: Remove `set -x` in the end. This is for debugging purposes only.
```bash
set -xeuEo pipefail
trap '__log_err ${FUNCNAME[0]:-"?"} ${BASH_COMMAND:-"?"} ${LINENO:-"?"} ${?:-"?"}' ERR
SCRIPT='name_of_this_script.sh'
function __log_err
{
printf "\n--- \e[1m\e[31mUNCHECKED ERROR\e[0m\n%s\n%s\n%s\n%s\n\n" \
" - script = ${SCRIPT:-${0}}" \
" - function = ${1} / ${2}" \
" - line = ${3}" \
" - exit code = ${4}" 1>&2
<CODE TO RUN AFTERWARDS>
}
```
### Comments, Descriptiveness & An Example
Comments should only describe non-obvious matters. Comments should start lowercase when they aren't sentences. Make the code **self-descriptive** by using meaningful names! Make comments not longer than approximately 80 columns, then wrap the line.
A positive example, which is taken from `start-mailserver.sh`, would be
```bash
function _setup_postfix_aliases
{
_notify 'task' 'Setting up Postfix Aliases'
: >/etc/postfix/virtual
: >/etc/postfix/regexp
if [[ -f /tmp/docker-mailserver/postfix-virtual.cf ]]
then
# fixing old virtual user file
if grep -q ",$" /tmp/docker-mailserver/postfix-virtual.cf
then
sed -i -e "s/, /,/g" -e "s/,$//g" /tmp/docker-mailserver/postfix-virtual.cf
fi
cp -f /tmp/docker-mailserver/postfix-virtual.cf /etc/postfix/virtual
# the `to` is important, don't delete it
# shellcheck disable=SC2034
while read -r FROM TO
do
# Setting variables for better readability
UNAME=$(echo "${FROM}" | cut -d @ -f1)
DOMAIN=$(echo "${FROM}" | cut -d @ -f2)
# if they are equal it means the line looks like: "user1 other@domain.tld"
[[ "${UNAME}" != "${DOMAIN}" ]] && echo "${DOMAIN}" >> /tmp/vhost.tmp
done < <(grep -v "^\s*$\|^\s*\#" /tmp/docker-mailserver/postfix-virtual.cf || true)
else
_notify 'inf' "Warning 'config/postfix-virtual.cf' is not provided. No mail alias/forward created."
fi
...
}
```
## YAML
When formatting YAML files, use [Prettier][prettier], an opinionated formatter. There are many plugins for IDEs around.
[semver]: https://semver.org/
[regex]: https://regex101.com/r/ikzJpF/7
[prettier]: https://prettier.io