Squeezebox: Keep track of already added players

[molobrakos]

Description:

Keep track of already added players.
When running hass e.g. inside a docker container using the bridge network, a squeezeserver might be discovered multiple times on multiple networks.

Related issue (if applicable): fixes #

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.github.io#<home-assistant.github.io PR number goes here>

Example entry for configuration.yaml (if applicable):

Checklist:

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

• Documentation added/updated in home-assistant.github.io

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

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[mention-bot]

@molobrakos, thanks for your PR! By analyzing the history of the files in this pull request, we identified @persandstrom, @dasos and @fabaff to be potential reviewers.

[pvizeli]

Please look to sonos and use unique_id from entity to handle that.

[houndci-bot]

line too long (93 > 79 characters)

[houndci-bot]

line too long (81 > 79 characters)

[molobrakos]

@pvizeli , thanks for pointing that out. I can see that implementing the unique_id property is enough, since at https://github.com/home-assistant/home-assistant/blob/master/homeassistant/helpers/entity_component.py#L179 there is a check to prevent an entity with the same unique_id to be added twice.

Let me know if it still is preferred to locally keep track of already added entities inside the platform (e.g. storing in hass.data), and check before passing to add_devices (the typical use case will only have one server with unique players anyway)