If the current planning holds, Robot 7.5 will include test metadata. See #4409.

We already have suite metadata.

Does it make sense to complete the list with Keyword metadata?

Why this may be useful

Recently, I've come up with some separate use cases that could benefit from keyword metadata.

1. Concurrency settings

Medusa uses suite metadata to calculate which tests can run in parallel. It's a clever approach that can be stretched. A tool like Medusa could use keyword metadata like a kind of lock.

The concept of locks already exists with keyword calls in PabotLib. It can be used to prevent multiple test processes from doing the same thing at the same time. For example, when writing to a file you want to lock that operation to prevent race conditions that cause corrupted files. This approach would be metadata-based instead of keyword-based. This could look something like:

Update A Data File
    [Arguments]    ${path}    ${new_content}
    [Metadata]    medusa:lock
    # change the file

Or, maybe

Update A Data File
    [Arguments]    ${path}    ${new_content}
    [Medusa]    lock
    # change the file

3. Caching

In CacheLibrary, I now use a keyword to retrieve from cache and another to write to cache. I got a feature request to cache with a listener instead (Lakitna/robotframework-cache#9).

A configuration like this could be made with metadata:

Do Expensive Calculation
    [Arguments]    ${data}
    [Cache]    1 hour
    # do a 10-minute calculation

3. Decorator

While writing this, I keep thinking that these examples are essentially Python's @decorators.

@amazing_decorator
def some_function:
    pass

With keyword metadata, this can be made in Robot like:

Some Keyword
    [Metadata]    amazing_decorator

On the Library-side, this should be implemented in a listener. If the listener encounters their special metadata string (here: amazing_decorator), it can wrap the keyword like a Python decorator does. The library can now, essentially do advanced keyword setup and teardown.

4. Temporary Library config

Keyword metadata could be used to overwrite some library configs if the library supports this.

Wait For Super Long And Annoying Animation
    [Selenium:timeout]    10 minutes

This would require explicit support from the libraries.

Existing alternatives

To make something like this now, you'd have to use tags, magic docstrings, stick with keywords, or use [Setup] and [Teardown].

Magic tags

Do Expensive Calculation
    [Arguments]    ${data}
    [Tags]    cache:3600
    # do a 10-minute calculation

Magic docstrings

Do Expensive Calculation
    [Documentation]    Lorum ipsum dolor sit amet
    ...  *CACHE:3600*
    [Arguments]    ${data}
    # do a 10-minute calculation

Keywords

Do Expensive Calculation
    [Arguments]    ${data}
    ${cached} =    Cache Retrieve value    amazing_key
    IF    $cached is not $None
        RETURN    ${cached}
    END

    # do a 10-minute calculation

    Cache Store Value    amazing_key    ${outcome}
    RETURN    ${outcome}

Setup and Teardown settings

Update A Data File
    [Arguments]    ${data}
    [Setup]    Cache Retrieve value
    # do a 10-minute calculation
    [Teardown]    Cache Store value

Non-library uses

I'm not sure if this is useful outside the library uses outlined above. I guess you could use it for documentation purposes, but I don't really see the point in a world where [Documentation] and [Tags] already exist.