ESPHome should not error when allow_other_uses is set and pin is not used anywhere else

[tjhorner]

Describe the problem you have/What new integration you would like

Starting in ESPHome 2023.12, ESPHome introduced a validation-time check to ensure that pins used in multiple places are explicitly marked as such, preventing unintended consequences of having multiple components use a pin. It will throw an error if a pin is used in multiple places but not marked with allow_other_uses; however, the inverse is also true, and I don't think this should be the case.

Please describe your use case for this integration and alternatives you've tried:

As a maintainer of ESPHome packages, I will want to give my users the option to reuse pins however they want in their own config. So for components unlikely to cause issues when used in multiple places I will add allow_other_uses: true. However, if the pin is not used in any additional places in the user's own config, ESPHome will throw an error and not let the user proceed. (Example: tjhorner/esphome-standing-desk#7)

Additionally, if a user wants to include a package where allow_other_uses: true is not set on a pin they want to reuse, there is no way to do so other than forking and modifying the package to include this.

I don't think it makes sense for ESPHome to outright error during validation if a pin has allow_other_uses set but is not used anywhere else; a warning would suffice in my opinion. Users should also be able to disable this check on pins either conditionally (e.g., with a comment) or entirely (e.g., with a command-line flag or as an option in the esphome: component).

I understand the implications of using a pin in multiple components and I appreciate the goal of this validation check, but it is not very ergonomic to use without an option to disable or reduce the severity of it, especially when using packages.

Additional context

[jldesignseu]

I kind of have a same request but in diferent scenario.

I have shift registeres for input and outputs (74hc165 and 74hc595) sharing pins between each other, so that on 4-5 gpio pins i can have 8x n times inputs/outputs.

In my case now when i describe my IO pin and I use CONF_NUMBER for PIN_SCHEMA I get an error that the pin "is used in multiple places." And when I modify my init.py with cv.Optional("allow_other_uses", default=True): cv.boolean then I get "incorrectly sets allow_other_uses: true." for every IO thatn is not used more then once.

Only solution for me is to go trough the pins and manually mark them as allow_other_uses but only for those that are used more then once.

It would be nice to mark them in schema as possibly_multiply_use so it won't generate errors and warnings.

combo74shreg:
  - id: 'combo74shreg_hub'
    data_pin: 16
    clock_pin: 15
    latch_pin: 14
    load_pin: 0
    oe_pin: 13
    sr_count: 4
binary_sensor:
  - platform: gpio
    name: ${node_name}_input_01
    pin:
      combo74shreg: combo74shreg_hub
      number: 0
      mode: input
switch:
  - platform: gpio
    name: ${node_name}_output_01
    pin:
      combo74shreg: combo74shreg_hub
      number: 0
      mode: output
      inverted: False

[ssieb]

You should never include that option in your component directly. Make a distinction between the input and output pins.