fix(core): Attribute decorator attributeName is mandatory

[ajitsinghkaler]

Attribute decorator has defined attributeName as optional but actually its
mandatory and compiler throwa an error if attributeName is undefined. Made
attributeName mandatory in the Attribute decorator to reflect this functionality

Fixes #32658

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.io application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Issue Number: #32658

What is the new behavior?

Does this PR introduce a breaking change?

• Yes
• No

Other information

[sonukapoor]

@ajitsinghkaler Are there any tests that cover this change?

[ajitsinghkaler]

I don't think it is a breaking change because if the attributeName is left empty it will give you an error already. So eveybody should already be following it's just that we have not enforced it.

[ajitsinghkaler]

@sonukapoor Actually I'm a bit confused if a test is actually needed for this because the attribute was already optional

I actually don't know even what actually to test for example should we test if the attributeName is empty it should throw but that was already happening. A bit confused by this

[sonukapoor]

@sonukapoor Actually I'm a bit confused if a test is actually needed for this because the attribute was already optional

I actually don't know even what actually to test for example should we test if the attributeName is empty it should throw but that was already happening. A bit confused by this

I assume there is already a unit test for this, that checks if the attributeName is not passed, then an error is thrown. Can you just double-check for that?

[crisbeto]

I don't know if that's actually the reason, but something to consider: maybe the idea with keeping the attributeName optional was that, if it omitted, the name would be picked up from the property that was decorated with it?

[ajitsinghkaler]

I don't think so even in docs it is not optional. Maybe not sure why but did not find anything like that

[jelbourn]

LGTM, if this throws an error already, I don't see this as a breaking change

Reviewed-for: public-api

[IgorMinar]

LGTM!

Considering that there is no way to inject an attribute without also specifying the attribute name, this change is not a breaking change and therefor it should be fine to land it without much trouble.

If google3 presubmits pass, then we can go as far as landing this in a patch version.

Reviewed-for: public-api

[petebacondarwin]

Reviewed-for: public-api

[jelbourn]

@AndrewKushnir PTAL

[ajitsinghkaler]

Should we add it to patch version

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