dotdrop/CONTRIBUTING.md

Content

* [code base](#code-base)
* [config parsing](#config-parsing)
  * [lower layer](#lower-layer)
  * [higher layer](#higher-layer)
  * [Precedence](#precedence)
  * [variables resolution](#variables-resolution)
  * [rules](#rules)
* [testing](#testing)
  * [testing with unittest](#testing-with-unittest)
  * [testing with bash scripts](#testing-with-bash-scripts)
* [documentation](#documentation)

Thanks for helping out!

Feature requests, bug reports and PRs are always welcome!

This file provides a few pointers on how to contribute to dotdrop
and where to find information. For any question, feel free to open an issue.

For PR adding new features, I'd be very thankful if you could add either
a unittest for the added feature or a bash script test (see [testing](#testing)), thanks!

# code base

Dotdrop's code base is located in the [dotdrop directory](/dotdrop).

Here's an overview of the different files and their role:

* **action.py**: represent the actions and transformations
* **cfg_yaml.py**: the lower level config parser (see [lower layer](#lower-layer))
* **cfg_aggregator.py**: the higher level config parser (see [higher layer](#higher-layer))
* **comparator.py**: the class handling the comparison for `compare`
* **dictparser.py**: abstract class for parsing dictionaries
* **dotdrop.py**: the entry point and where the different cli commands are executed
* **dotfile.py**: represent a dotfile
* **installer.py**: the class handling the installation of dotfile for `install`
* **jhelpers.py**: list of methods available in templates with jinja2
* **linktypes.py**: enum for the three types of linking (none, symlink, children)
* **logger.py**: the custom logger
* **options.py**: the class embedding all the different options across dotdrop
* **profile.py**: represent a profile
* **settings.py**: represent the config settings
* **templategen.py**: the jinja2 templating class
* **updater.py**: the class handling the update of dotfiles for `update`
* **utils.py**: some useful methods used across the code base

# config parsing

The configuration file (yaml) is parsed using two layers:

  * first in the lower layer in [cfg_yaml.py](/dotdrop/cfg_yaml.py)
  * then in the higher layer in [cfg_aggregator.py](/dotdrop/cfg_aggregator.py)

Only the higher layer is accessible to other classes of dotdrop.

## lower layer

This is done in [cfg_yaml.py](/dotdrop/cfg_yaml.py)

The lower layer part is only taking care of basic types
and does the following:
  * normalize all config entries
    * resolve paths (dotfiles src, dotpath, etc)
    * refactor actions/transformations to a common format
    * etc
  * import any data from external files (configs, variables, etc)
  * apply variable substitutions
  * complete any data if needed (add the "profile" variable, etc)
  * execute intrepreted variables through the shell
  * write new entries (dotfile, profile) into the dictionary and save it to a file
  * fix any deprecated entries (link_by_default, etc)
  * clear empty entries

In the end it builds a cleaned and normalized dictionary to be accessed by the higher layer.

## higher layer

This is done in [cfg_aggregator.py](/dotdrop/cfg_aggregator.py)

The higher layer will transform the dictionary parsed by the lower layer
into objects (profiles, dotfiles, actions, transformations, etc).
The higher layer has no notion of inclusion (profile included for example) or
file importing (import actions, etc) or even interpreted variables
(it only sees variables that have already been interpreted).

It does the following:
  * transform dictionaries into objects
  * patch list of keys with its corresponding object (for example dotfile's actions)
  * provide getters for every other classes of dotdrop needing to access elements

Note that any change to the yaml dictionary (adding a new profile or a new dotfile for
example) won't be *seen* by the higher layer until the config is reloaded. Consider the
`dirty` flag as a sign the file needs to be written and its representation in higher
levels in not accurate anymore.

## precedence

* `dynvariables` > `variables`
* profile `(dyn)variables` > any other `(dyn)variables`
* profile `(dyn)variables` > profile's included `(dyn)variables`
* imported `variables`/`dynvariables` > `(dyn)variables`

## variables resolution

How variables are resolved (through jinja2's
templating) in the config file.

* resolve main config file variables
  * merge `variables` and `dynvariables` (allowing cycling reference)
  * recursively template merged `variables` and `dynvariables`
  * `dynvariables` are executed
  * profile's `variables` and `dynvariables` are merged
* resolve *included* entries (see below)
  * paths and entries are templated
    (allows to use something like `include {{@@ os @@}}.variables.yaml`)
* *included* entries are processed
  * dyn-/variables are all resolved in their own file

potential *included* entries

* entry *import_actions*
* entry *import_configs*
* entry *import_variables*
* profile's *import*
* profile's *include*

Variables are then used to resolve different elements in the config file:
see [this](docs/config.md#variables)

## rules

* `dynvariables` are executed in their own config file
* since `variables` and `dynvariables` are templated before the `dynvariables`
  are executed, this means that `dynvariables` can safely reference `variables` however
  `variables` referencing `dynvariables` will result with the *not-executed* value of the
  referenced `dynvariables` (see examples below)
* profile cannot include profiles defined above in the import tree
* config files do not have access to variables defined above in the import tree
* actions/transformations using variables are resolved at runtime
  (when action/transformation is executed) and not when loading the config

This will result with `dvar0 = "test"` and `var0 = "echo test"` (**not** `var0 = test`)
```yaml
variables:
  var0: "{{@@ dvar0 @@}}"
dynvariables:
  dvar0: "echo test"
```

This will result with `dvar0 = "test"` and `var0 = "test"`
```yaml
variables:
  var0: "test"
dynvariables:
  dvar0: "echo {{@@ var0 @@}}"
```


# testing

Dotdrop is tested with the use of the [tests.sh](/tests.sh) script.

* test for PEP8 compliance with `pycodestyle` and `pyflakes`
* run the unittest available in [tests directory](/tests)
* run the bash script tests in [tests-ng directory](tests-ng)

## testing with unittest

All unittests are available in [tests directory](/tests)
and use [python unittest](https://docs.python.org/3/library/unittest.html).

The file [helpers.py](/tests/helpers.py) provides different helper methods
for the tests.

## testing with bash scripts

The bash scripts are available in [tests-ng directory](tests-ng).
These test entire workflows by simulating the use of dotdrop from end to end
for different use-cases (usually described in their filename or in the file header).

Each script starts with the same boiler plate code that you can paste at the
start of your new test (see the head of the file down to `# this is the test`).

# documentation

Dotdrop documentation is available under [https://dotdrop.readthedocs.io/](https://dotdrop.readthedocs.io/).