esphome-docs/guides/contributing.rst

Contributing
============

.. seo::
    :description: Getting started guide for contributing to the ESPHome project
    :image: github-circle.png

Contributions to the ESPHome suite are very welcome! All the code for the projects
is hosted on GitHub and you can find the sources here:

- `ESPHome <https://github.com/esphome/esphome>`__ (Project Source Code)
- `ESPHome-Docs <https://github.com/esphome/esphome-docs>`__ (The documentation which you're reading here)

Just clone the repository locally, do the changes for your new feature/bug fix and submit
a pull request.

Contributing to ESPHome-Docs
----------------------------

.. figure:: /images/logo-docs.svg
    :align: center
    :width: 60.0%

One of the areas of ESPHome that can always be improved is the documentation.
If you see an issue somewhere, a spelling mistakes or if you want to share your awesome
setup, please feel free to submit a pull request.

The ESPHome documentation is built using `sphinx <http://www.sphinx-doc.org/>`__ and uses
`reStructuredText <http://docutils.sourceforge.net/rst.html>`__ for all source files.

Syntax
******

Here's a quick RST primer:

Title hierarchy is based on order of occurrence, not on type of character used to underline it. This
documents establish the following character order for better consistency.

- **Headers**: You can write titles like this:

  .. code-block:: rst

      My Title
      ========

  and section headers like this:

  .. code-block:: rst

      My Sub Section
      --------------

  and sub-section headers like this:

  .. code-block:: rst

      My Sub-sub Section
      ******************

  .. note::

      The length of the bar below the text **must** match the title Text length.
      Also, titles should be in Title Case

- **Links**: To create a link to an external resource (for example https://www.google.com), use
  ``\`Link text <link_url>\`__``. For example:

  .. code-block:: rst

      `Google.com <https://www.google.com>`__

  `Google.com <https://www.google.com>`__

- **References**: To reference another document, use the ``:doc:`` and ``:ref:`` roles (references
  are set up globally and can be used between documents):

  .. code-block:: rst

      .. _my-reference-label:

      Section to cross-reference
      --------------------------

      See :ref:`my-reference-label`, also see :doc:`/components/switch/gpio`.
      :doc:`Using custom text </components/switch/gpio>`.

  See :ref:`devices`, also see :doc:`/components/switch/gpio`.
  :doc:`Using custom text </components/switch/gpio>`.

- **Inline code**: To have text appear ``like this``, use double backticks:

  .. code-block:: rst

      To have text appear ``like this``, use double backticks.

  To have text appear ``like this``, use double backticks.

- **Code blocks**: To show a sample configuration file, use the ``code-block`` directive:

  .. code-block:: rst

      .. code-block:: yaml

          # Sample configuration entry
          switch:
            - platform: gpio
              name: "Relay #42"
              pin: GPIO13

  .. code-block:: yaml

      # Sample configuration entry
      switch:
        - platform: gpio
          name: "Relay #42"
          pin: GPIO13

  .. note::

      Please note the empty line after the ``code-block`` directive. That is necessary.

- **Images**: To show images, use the ``figure`` directive:

  .. code-block:: rst

      .. figure:: images/dashboard.png
          :align: center
          :width: 40.0%

          Optional figure caption.

  .. figure:: images/dashboard.png
      :align: center
      :width: 40.0%

      Optional figure caption.

  .. note::

      All images in the documentation need to be as small as possible to ensure
      fast page load times. For normal figures the maximum size should be at most
      about 1000x800 px or so. Additionally, please use online tools like
      https://tinypng.com/ or https://tinyjpg.com/ to further compress images.

- **Notes and warnings**: You can create simple notes and warnings using the ``note`` and ``warning``
  directives:

  .. code-block:: rst

      .. note::

          This is a note.

      .. warning::

          This is a warning.

  .. note::

      This is a note.

  .. warning::

      This is a warning.

- **Italic and boldface font families**: To *italicize* text, use one asterisk around the text. To put
  **a strong emphasis** on a piece of text, put two asterisks around it.

  .. code-block:: rst

      *This is italicized.* (A weird word...)
      **This is very important.**

  *This is italicized.* (A weird word...)
  **This is very important.**

- **Ordered and unordered list**: The syntax for lists in RST is more or less the same as in Markdown:

  .. code-block:: rst

      - Unordered item

        - Unordered sub-item

      - Item with a very long text so that it does not fully fit in a single line and
        must be split up into multiple lines.

      1. Ordered item #1
      2. Ordered item #2

  - Unordered item

    - Unordered sub-item

  - Item with a very long text so that it does not fully fit in a single line and
    must be split up into multiple lines.

  1. Ordered item #1
  2. Ordered item #2

- **imgtable**: ESPHome uses a custom RST directive to show the table on the front page (see
  `index.rst <https://github.com/esphome/esphome-docs/blob/current/index.rst>`__).
  New pages need to be added to the ``imgtable`` list. The syntax is CSV with <PAGE NAME>, <FILE NAME> (without RST),
  <IMAGE> (in top-level images/ directory), <COMMENT> (optional - short text to describe the component). The aspect ratio of these images should be 8:10 (or 10:8) but exceptions are possible.

  Because these images are served on the main page, they need to be compressed heavily. SVGs are preferred over JPGs
  and JPGs should be max. 300x300px.
  If you have imagemagick installed, you can use this command to convert the thumbnail:

  .. code-block:: bash

      convert -sampling-factor 4:2:0 -strip -interlace Plane -quality 80% -resize 300x300 in.jpg out.jpg

reStructured text can do a lot more than this, so if you're looking for a more complete guide
please have a look at the `Sphinx reStructuredText Primer <http://www.sphinx-doc.org/en/master/usage/restructuredtext/basics.html>`__.

Build
*****

.. note::

    The easiest way is to use the `esphome-docs Docker image <https://hub.docker.com/r/esphome/esphome-docs/>`__:

    .. code-block:: bash

        docker run --rm -v "${PWD}/":/data/esphomedocs -p 8000:8000 -it esphome/esphome-docs

    With ``PWD`` referring to the root of the ``esphome-docs`` git repository. Then go to ``<CONTAINER_IP>:8000`` in your browser.

    This way, you don't have to install the dependencies to build the documentation.

To check your documentation changes locally, you first need install Sphinx (with **Python 3**).

.. code-block:: bash

    # in ESPHome-Docs repo:
    pip install -r requirements.txt

Then, use the provided Makefile to build the changes and start a simple web server:

.. code-block:: bash

    # Start web server on port 8000
    make webserver

    # Updates then happen via:
    make html

Notes
*****

Some notes about the docs:

- Use the English language (duh...)
- An image tells a thousand words, please use them wherever possible. But also don't forget to shrink them, for example
  I often use https://tinypng.com/
- Try to use examples as often as possible (also while it's great to use highly accurate,
  and domain-specific lingo, it should not interfere with new users understanding the content)
- Fixes/improvements for the docs themselves should go to the ``current`` branch of the
  esphomedocs repository. New features should be added against the ``next`` branch.
- Always create new branches in your fork for each pull request.

.. _setup_dev_env:

Setting Up Development Environment
----------------------------------

For developing new features to ESPHome, you will first need to set up a development environment.
This is only possible for ``pip`` installs.

.. code-block:: bash

    # Clone repos
    git clone https://github.com/esphome/esphome.git
    git clone https://github.com/esphome/esphome-docs.git

    # Install ESPHome
    cd esphome/
    script/setup
    # Start a new feature branch
    git checkout -b my-new-feature
    cd ..

Now you can open ESPHome in your IDE of choice (mine is CLion) with the PlatformIO
addons (see PlatformIO docs for more info). Then develop the new feature with the
guidelines below.

All PRs are automatically checked for some basic formatting/code mistakes with Github Actions.
These checks *must* pass for your PR to be mergeable.

Setting Up Git Environment
--------------------------

ESPHome's code-base is hosted on GitHub, and contributing is done exclusively through
"Pull Requests" (PRs) in the GitHub interface. So you need to set up your git environment
first.

When you want to create a patch for ESPHome, first go to the repository you want to contribute to
(esphome, etc) and click fork in the top right corner. This will create
a fork of the repository that you can modify and create git branches on.

.. code-block:: bash

    # Clone your fork
    git clone https://github.com/<YOUR_GITHUB_USERNAME>/<REPO_NAME>.git
    # For example: git clone https://github.com/OttoWinter/esphome.git

    # Add "upstream" remote
    git remote add upstream https://github.com/esphome/<REPO_NAME>.git
    # For example: git remote add upstream https://github.com/esphome/esphome.git

    # For each patch, create a new branch from latest dev
    git checkout dev
    git pull upstream dev
    git checkout -b <MY_NEW_FEATURE>
    # For example: git checkout -b gpio-switch-fix

    # Make your modifications, then commit changes with message describing changes
    git add .
    git commit -m "<COMMIT_MESSAGE>"
    # For example: git commit -m "Fix GPIO Switch Not Turning Off Interlocked Switches"

    # Upload changes
    git push -u origin <BRANCH_NAME>
    # For example: git push -u origin gpio-switch-fix

Then go to your repository fork in GitHub and wait for a create pull request message to show
up in the top (alternatively go to branches and create it from there). Fill out the
Pull Request template outlining your changes; if your PR is not ready to merge yet please
mark it as a draft PR in the dropdown of the green "create PR" button.

**Review Process:** ESPHome's code base tries to have a high code standard. At the bottom
of the Pull Request you will be able to see the "Github Actions" continuous integration check which
will automatically go through your patch and try to spot errors. If the CI check fails,
please see the Github Actions log and fix all errors that appear there. Only PRs that pass the automated
checks can be merged!

**Catching up with reality**: Sometimes other commits have been made to the same files
you edited. Then your changes need to be re-applied on top of the latest changes with
a "rebase". More info `here <https://developers.home-assistant.io/docs/en/development_catching_up.html>`__.

.. code-block:: bash

    # Fetch the latest upstream changes and apply them
    git fetch upstream dev
    git rebase upstream/dev

Contributing to ESPHome
-----------------------

.. figure:: /images/logo-text.svg
    :align: center
    :width: 60.0%

This is a guide to contributing to the ESPHome codebase. ESPHome uses two languages for its project:
Python and C++.

The user configuration is read, validated and transformed into a custom firmware
with the Python side of the firmware.

The C++ codebase is what's actually running on the ESP and called the "runtime". This part of
the codebase should first set up the communication interface to a sensor/component/etc. and
communicate with the ESPHome core via the defined interfaces (like Sensor, BinarySensor, Switch).

1. Directory Structure
**********************

After you've :ref:`set up development environment <setup_dev_env>`, you will have a folder structure
like this:

.. code-block:: text

    esphome
    ├── __main__.py
    ├── automation.py
    ├── codegen.py
    ├── config_validation.py
    ├── components
    │   ├── __init__.py
    │   ├── dht12
    │   │   ├── __init__.py
    │   │   ├── dht12.cpp
    │   │   ├── dht12.h
    │   │   ├── sensor.py
    │   ├── restart
    │   │   ├── __init__.py
    │   │   ├── restart_switch.cpp
    │   │   ├── restart_switch.h
    │   │   ├── switch.py
    │  ...

As you can see, all components are in the "components" folder. Each component is in its own
subfolder which contains the Python code (.py) and the C++ code (.h and .cpp).

Suppose the user types in the following:

.. code-block:: yaml

    hello1:

    sensor:
      - platform: hello2

In both cases, ESPHome will automatically look for corresponding entries in the "components"
folder and find the directory with the given name. For example the first entry will make ESPHome
look at the ``esphome/components/hello1/__init__.py`` file and the second entry will result in
``esphome/components/hello2/sensor.py``.

Let's leave what's written in those files for (2.), but for now you should also know that
whenever a component is loaded, all the C++ source files in the folder of the component
are automatically copied into the generated PlatformIO project. So you just need to add the C++
source files in the folder and the ESPHome core will copy them with no additional code required
by the integration developer.

.. note::

    For testing you can use :doc:`/components/external_components`.

    ESPHome also has a ``custom_components`` mechanism like `Home Assistant does
    <https://developers.home-assistant.io/docs/creating_component_index>`__. However this is
    discouraged in favor of :doc:`/components/external_components`.

2. Config Validation
********************

The first thing ESPHome does is read and validate the user config. For this ESPHome has a powerful
"config validation" mechanism. Each component defines a config schema that is validated against
the user config.

To do this, all ESPHome Python modules that can be configured by the user have a special field
called ``CONFIG_SCHEMA``. An example of such a schema is shown below:

.. code-block:: python

    import esphome.config_validation as cv

    CONF_MY_REQUIRED_KEY = 'my_required_key'
    CONF_MY_OPTIONAL_KEY = 'my_optional_key'

    CONFIG_SCHEMA = cv.Schema({
      cv.Required(CONF_MY_REQUIRED_KEY): cv.string,
      cv.Optional(CONF_MY_OPTIONAL_KEY, default=10): cv.int_,
    }).extend(cv.COMPONENT_SCHEMA)

This variable is automatically loaded by the ESPHome core and validated against.
The underlying system ESPHome uses for this is `voluptuous <https://github.com/alecthomas/voluptuous>`__.
Going into how to validate is out of scope for this guide, but the best way to learn is to look
at examples of how similar integrations validate user input.

A few point on validation:

- ESPHome puts a lot of effort into **strict validation** - If possible, all validation methods should be as strict
  as possible and detect wrong user input at the validation stage (and not later).
- All default values should be defined in the schema (and not in C++ codebase or other code parts).
- Config keys should be descriptive - If the meaning of a key is not immediately obvious you should
  always prefer long_but_descriptive_keys.

3. Code Generation
******************

After the user input has been successfully validated, the last step of the Python codebase
is called: Code generation.

As you may know, ESPHome converts the user's configuration into C++ code (you can see the generated
code under ``<NODE_NAME>/src/main.cpp``). Each integration must define its own ``to_code`` method
that converts the user input to C++ code.

This method is also automatically loaded and invoked by the ESPHome core. An example of
such a method can be seen below:

.. code-block:: python

    import esphome.codegen as cg

    def to_code(config):
        var = cg.new_Pvariable(config[CONF_ID])
        yield cg.register_component(var)

        cg.add(var.set_my_required_key(config[CONF_MY_REQUIRED_KEY]))

Again, going into all the details of ESPHome code generation would be out-of-scope. However,
ESPHome's code generation is 99% syntactic sugar - and again it's probably best to study other
integrations and just copy what they do.

There's one important concept for the ``to_code`` method: coroutines with ``yield``.
First the problem that leads to coroutines: In ESPHome, integrations can declare (via ``cg.Pvariable``) and access variables
(``cg.get_variable()``) - but sometimes when one part of the code base requests a variable
it has not been declared yet because the code for the component creating the variable has not run yet.

To allow for ID references, ESPHome uses so-called ``coroutines``. When you see a ``yield`` statement
in a ``to_code`` method, ESPHome will call the provided method - and if that method needs to wait
for a variable to be declared first, ``yield`` will wait until that variable has been declared.
After that, ``yield`` returns and the method will execute on the next line.

Next, there's a special method - ``cg.add`` - that you will often use. ``cg.add()`` does a very simple
thing: Any C++ declared in the parentheses of ``cg.add()`` will be added to the generated code.
If you do not call "add" a piece of code explicitly, it will not be added to the main.cpp file!

4. Runtime
**********

Okay, the Python part of the codebase is now complete - now let's talk about the C++ part of
creating a new integration.

The two major parts of any integration roughly are:

 - Setup Phase
 - Run Phase

When you create a new integration, your new component will inherit from :apiclass:`Component`.
That class has a special ``setup()`` method that will be called once to set up the component -
at the time the ``setup()`` method is called, all the setters generated by the Python codebase
have already run and the all fields are set for your class.

The ``setup()`` method should set up the communication interface for the component and check
if communication works (if not, it should call ``mark_failed()``).

Again, look at examples of other integrations to learn more.

The next thing that will be called with your component is ``loop()`` (or ``update()`` for a
:apiclass:`PollingComponent`). In these methods you should retrieve the latest data from the
component and publish them with the provided methods. One thing to note in these methods
is that anything in ``loop()`` or ``setup()`` **should not block**. Specifically methods like
``delay(10)`` should be avoided and delays above ~10ms are not permitted. The reason for this
is that ESPHome uses a central single-threaded loop for all components - if your component
blocks the whole loop will be slowed down.

Finally, your component should have a ``dump_config`` method that prints the user configuration.

5. Extras
*********

.. note::

    This serves as documentation for some of ESPHome's internals and is not necessarily part of the
    development guide.

All Python modules have some magic symbols that will automatically be loaded by the ESPHome
loader. These are:

- ``CONFIG_SCHEMA``: The configuration schema to validate the user config against.
- ``to_code``: The function that will be called with the validated configuration and should
  create the necessary C++ source code.
- ``DEPENDENCIES``: Mark the component to depend on other components. If the user hasn't explicitly
  added these components in their configuration, a validation error will be generated.
- ``AUTO_LOAD``: Automatically load an integration if the user hasn't added it manually.
- ``MULTI_CONF``: Mark this component to accept an array of configurations. If this is an
  integer instead of a boolean, validation will only permit the given number of entries.
- ``CONFLICTS_WITH``: Mark a list of components as conflicting with this integration. If the user
  has one of them in the config, a validation error will be generated.

- ``ESP_PLATFORMS``: Provide a list of allowed ESP types this integration works with.
- ``CODEOWNERS``: GitHub usernames or team names of people that are responsible for this integration.
  You should add at least your GitHub username here, as well as anyone who helped you to write code
  that is being included.

Codebase Standards
------------------

Standard for the esphome-core codebase:

- The C++ code style is based on the
  `Google C++ Style Guide <https://google.github.io/styleguide/cppguide.html>`__ with a few modifications.

    - function, method and variable names are ``lower_snake_case``
    - class/struct/enum names should be ``UpperCamelCase``
    - constants should be ``UPPER_SNAKE_CASE``
    - fields should be ``protected`` and ``lower_snake_case_with_trailing_underscore_`` (DO NOT use private)
    - It's preferred to use long variable/function names over short and non-descriptive ones.
    - All uses of class members and member functions should be prefixed with
      ``this->`` to distinguish them from global functions in code review.
    - Use two spaces, not tabs.
    - Using ``#define`` s is discouraged and should be replaced with constants.
    - Use ``using type_t = int;`` instead of ``typedef int type_t;``

- New components should dump their configuration using ``ESP_LOGCONFIG``
  at startup in ``dump_config()``
- ESPHome uses a unified formatting tool for all source files (but this tool can be difficult to install).
  When creating a new PR in GitHub, see the Github Actions output to see what formatting needs to be changed
  and what potential problems are detected.

- The number of external libraries should be kept to a minimum. If the component you're developing has a simple
  communication interface, please consider implementing the library natively in ESPHome.

  - This depends on the communication interface of course - if the library is directly working
    with pins or doesn't do any I/O itself, it's ok. However if it's something like I²C, then ESPHome's
    own communication abstractions should be used. Especially if the library accesses a global variable/state
    like ``Wire`` there's a problem because then the component may not modular (i.e. not possible
    to create two instances of a component on one ESP)

- Integrations **must** use the provided abstractions like ``Sensor``, ``Switch`` etc.
  Integration should specifically **not** directly access other components like for example
  publish to MQTT topics.

- Implementations for new devices should contain reference links for the datasheet and other sample
  implementations.
- Please test your changes :)

.. note::

    You can also run the lint and Github Actions checks through a docker image:

    .. code-block:: bash

        # Full lint+test suite
        docker run --rm -v "${PWD}/":/esphome -it esphome/esphome-lint script/fulltest

        # Run lint only over changed files
        docker run --rm -v "${PWD}/":/esphome -it esphome/esphome-lint script/quicklint

ESPHome via Gitpod
******************

An alternative to a local checkout and build is doing so via `Gitpod <https://www.gitpod.io>`__.
ESPHome will be installed for you and the dashboard wizard will run on startup.

You can also run the steps manually.

.. code-block:: bash

    python setup.py install

To start a command line wizard, run

.. code-block:: bash

    python esphome my_configuration.yaml wizard

To get the web-based dashboard, use

.. code-block:: bash

    python esphome my_configuration.yaml dashboard

and allow exposing the web app at port 6052.

See Also
--------

- :doc:`ESPHome index </index>`
- :doc:`faq`
- :ghedit:`Edit`