---
layout: default
title: Plugin rpkg preprocessor
---

This plugin allows you to run preprocessing on an input spec file just before srpm build is started.

Preprocessing is implemented by a simple `preproc` language which allows you to place: `{% raw %}{{{ bash_code }}}{% endraw %}` tags into any text file. When you run such text file through `preproc` command-line utility, a "rendered" text file is output where all the `{% raw %}{{{ bash_code }}}{% endraw %}` tags are now replaced by standard output of the executed `bash_code` that was inside the `{% raw %}{{{ }}}{% endraw %}` tags.

`preproc` also allows you to load a certain library of macros (by `-s` switch on its command-line) which are essentially just bash functions that you can afterward use from any `{% raw %}{{{ }}}{% endraw %}` tag in the input text file.

One such library is called `rpkg-macros` and its macros are documented [here](https://docs.pagure.org/rpkg-util/v3/macro_reference.html). These macros are specialized to render rpm spec file's dynamically based on surrounding git metadata. They need the spec file you are building srpm from to be placed in a git repository.

`preproc` with the `rpkg-macros` library loaded is exactly what is used to perform preprocessing on spec file by the `rpkg_preprocessor` plugin. Instead of calling `preproc` directly with the `-s` switch to load `rpkg-macros`, we use a tiny `preproc-rpmspec` wrapper that does this for us but it could be done either way.

Note that just enabling the plugin is not enough to get spec file preprocessed. You additionally need `rpkg.conf` file placed next to the spec file with the following content:
```ini
[rpkg]
preprocess_spec = True
```
That's because for some packages you might want to have preprocessing disabled even though the plugin is globally enabled. Note that even if you have rpkg preprocessing globally enabled (e.g. in `/etc/mock/site-defaults.cfg`) and the `rpkg.conf` file is present with the required content to enable preprocessing, you still have an option to disable preprocessing on command-line by using mock's option `--disable-plugin=rpkg_preprocessor`. There is also `--enable-plugin=rpkg_preprocessor` to do the opposite.

There is currently only one mock command that does invoke the `rpkg_preprocessor` plugin (if all the conditions above are satisfied): `mock --buildsrpm`. This plugin is not employed for rebuilding existing srpms with `mock --rebuild` command or any other mock operation currently.

An example usage with the `mock --buildsrpm` command is:

    $ cd <package_git_repository>
    $ mock --buildsrpm --spec ./my_package.spec.rpkg --sources .

This will run preprocessing on `my_package.spec.rpkg` and the output spec file will be then handed over to `rpmbuild` to build srpm from it.

`.rpkg` extension for rpm spec files containing rpkg macros is optional but recommended.

## Configuration

The plugin supports the following configuration options (mentioned together with the default values):
```python
config_opts['plugin_conf']['rpkg_preprocessor_enable'] = False
config_opts['plugin_conf']['rpkg_preprocessor_opts']['requires'] = ['preproc-rpmspec']
config_opts['plugin_conf']['rpkg_preprocessor_opts']['cmd'] = '/usr/bin/preproc-rpmspec %(source_spec)s --output %(target_spec)s'
```

* `rpkg_preprocessor_enable` option switches the plugin on and off
* `requires` option specifies requirements to perform the preprocessing operation. The operation is done in a chroot where srpm is built afterwards so the tool(s) to perform preprocessing need to be installed there first
* `cmd` option defines the actual command to run the preprocessing operation.

`requires` and `cmd` options are there for possible future updates in the used tooling. You don't need to modify these options to get the default preprocessing functionality. The only line needed in `/etc/mock/site-defaults.cfg` to enable this plugin is:
```python
config_opts['plugin_conf']['rpkg_preprocessor_enable'] = True
```
This plugin is available since mock-x.x.x.