Add Derivative component

[afaucogney]

Description:

Here is the derivation component based on integration component.
This sensor will be useful:

• to get a feeling about evolution of another sensor
• to calculate the derivative of a sensor (ms -> m, kWh -> kW, m -> m/s)

Pull request with documentation for home-assistant.io (if applicable): home-assistant/home-assistant.io#10323

Example entry for configuration.yaml (if applicable):

sensor:
  - platform: random
    name: myRandom
    minimum: 0
    maximum: 10
    unit_of_measurement: v
  - platform: integration
    source: sensor.myRandom
    name: myIntegration
    unit_prefix: k
    round: 2
    unit_time: s
  - platform: derivative
    source: sensor.myRandom
    name: myDerivation
    unit: v/s
    unit_time: s
  - platform: derivative
    source: sensor.myDerivation
    name: mySecondDerivation
    unit: v/s2
    unit_time: s    

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[homeassistant]

Hi @afaucogney,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[afaucogney]

Hi, this is my first PR for HomeAssistant, and I'm not a python dev.
So please help me going further with that PR

[JeffLIrion]

This platform should be called differentiation, not derivation.

[afaucogney]

This platform should be called differentiation, not derivation.

@JeffLIrion are you sure of this. I m an not English, but for me differentiation does not take in account the time (so the dx). What do you think ?

[JeffLIrion]

The process of finding a derivative is called differentiation. The reverse process is called antidifferentiation. The fundamental theorem of calculus relates antidifferentiation with integration. Differentiation and integration constitute the two fundamental operations in single-variable calculus.

https://en.m.wikipedia.org/wiki/Derivative

[tsvi]

Or else call it derivative.

[afaucogney]

@tsvi as I said I m not either fluent in Python or homeassistant framework, so my test case always get 0 as the value to assert, so my test failed. However it seems to work in a real configuration.. I almost copy + adapt the code from integration, but have no clue what is wrong. Could you help me ?

[afaucogney]

@tsvi as I said I m not either fluent in Python or homeassistant framework, so my test case always get 0 as the value to assert, so my test failed. However it seems to work in a real configuration.. I almost copy + adapt the code from integration, but have no clue what is wrong. Could you help me ?

I fixed this, it was a question of rounding value.
However the prefix test doesn't work, and I have no idea why, any idea, help is welcome ? The implementation is the same as integration, but behave differently !

[Spirituss]

Looking forward for the release. Very useful component.

[balloob]

Remove this.

[balloob]

this is really unreadable. Please break it out into multiple statements.

[balloob]

This looks good. Ok to merge when final comments addressed and linting fixed.

[afaucogney]

This looks good. Ok to merge when final comments addressed and linting fixed.

@balloob thanks for the approval. I'm so young in python that I did succeed to mock the line that trigger the error handling. And this is required to achieve the expected coverage.

For exemple line 104:

        if state:
            try:
                self._state = Decimal(state.state)
            except ValueError as err:
                _LOGGER.warning("Could not restore last state: %s", err)

I need a test that mock Decimal() to then throw a ValueError(). Could you give me an exemple, and then I will apply to other cases.
I succeed to achieve this on a simple exemple, but the async def test...
This PR is mainly a copy for the integration component, so I do not know all what I'm doing ... But I will fix the rest if I can find a solution for the test / coverage.

[thomasloven]

In what case would decimal.Decimal() raise a ValueError?
I can not find any reference to it in the docs.

[afaucogney]

In what case would decimal.Decimal() raise a ValueError?
I can not find any reference to it in the docs.

I moved to SyntaxError

[springstan]

@afaucogney you have a couple of unused imports, please take a look at the Linting errors to spot and remove them from your code. Thanks!

[tkislan]

@afaucogney Will you be finishing this PR? I would very much like to use it in my home automation

If not, I can fork your fork, and finish it.

[afaucogney]

@afaucogney Will you be finishing this PR? I would very much like to use it in my home automation

If not, I can fork your fork, and finish it.

Hi @tkislan, thanks for your interest on my PR. I tried to fix some issue, if you think you may do better (I'm sure, cause I am a python novice), feel free to PR my branch, I will accept your contribution for sure !

[afaucogney]

Review done !

[springstan]

@afaucogney please fix your failing tests :)