Allow empty string titles in legacy notifier service

[mitchellwrosen]

Breaking change

What breaks
Explicitly configuring a legacy notifier to send a message with title: '' will no longer fall back on the default title of "Home Assistant"

How to make it work again
Delete title: '' entirely, or replace with title: Home Assistant

Why we did this
To allow empty string titles

Proposed change

I propose we tweak the logic that parses notification configuration and calls legacy notification services to explicitly allow empty titles. My motivation is integrating Home Assistant with https://github.com/caronc/apprise. In Apprise, notification titles are optional. For certain backends (like Discord), messages without titles look a lot better, as they can be shorter and don't have a superfluous newline.

I dug around in Git history a bit, and found the original intent was to allow None titles (i.e. missing title key in yaml configuration): #3100

This was followed up by some hotfix patch that introduced the current logic (almost 10 years ago!), which I believe accidentally conflates None with "" by using the truthiness of strings, rather than comparing to None directly: #3302

In this PR, I've just swapped the truthiness check for a direct comparison to None, exactly as we do a few lines below for ATTR_TARGET.

Type of change

• Dependency upgrade
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• Breaking change (fix/feature causing existing functionality to break)
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Stale

[Copilot]

Pull request overview

This PR adjusts the legacy notify service so that explicitly configured empty-string titles are forwarded as-is instead of being treated as missing and replaced with the default "Home Assistant", and adds regression tests to cover this behavior.

Changes:

• Updates the legacy notify service’s _async_notify_message_service to treat ATTR_TITLE as present whenever it is not None, allowing empty strings instead of relying on truthiness.
• Adds a YAML-script-based test to verify that an explicitly empty title (title: '') is forwarded unchanged through the legacy notify path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
homeassistant/components/notify/legacy.py	Adjusts ATTR_TITLE handling in _async_notify_message_service to check is not None and always forward explicitly provided titles, including empty strings.
tests/components/notify/test_legacy.py	Adds a new test ensuring that a script-driven notify call with title: '' forwards an empty title instead of falling back to the default.

[Copilot]

The new ATTR_TITLE handling now calls service.data.get(ATTR_TITLE) twice and leaves the annotated title variable unused; this makes the intent slightly harder to read and unnecessarily repeats the lookup. Consider restoring a single lookup that also makes the None check explicit, for example by assigning the result to a local variable (or using the walrus operator with an is not None comparison) before adding it to kwargs.

[mitchellwrosen]

I deleted the unused variable. I don't think it's a problem to repeat the lookup. It's consistent with the rest of the function as-is.

[Copilot]

The updated ATTR_TITLE logic is only covered via the new script-based test, but there is no direct service call test exercising an explicitly empty string title (e.g., calling notify.notify with title: ''). Adding a unit test similar to test_method_forwards_correct_data that verifies an empty string title is forwarded unchanged for a direct notify service call would better pin down this new behavior and guard against regressions.

[mitchellwrosen]

This isn't true, the test I added fails without the corresponding change to the code.

[MartinHjelmare]

I'm not following where the default title Home Assistant, that you mention, is coming from. There is no default in the changed code, that I can see.