[RFC] [2.2] Convert Timestamp for date widgets

[richardhj]

Description

Convert date widget values to timestamps on encode property value and vice-versa on decode property value.

Closes #415.

Checklist

• Read and understood the CONTRIBUTING guidelines
• Created tests, if possible
• All tests passing
• Extended the README / documentation, if necessary
• Added myself to the @authors in touched PHP files
• Checked the changes with phpcq and introduced no new issues

This code is simliar to https://github.com/MetaModels/attribute_timestamp/blob/2.0.4/src/MetaModels/Attribute/Timestamp/BootSubscriber.php#L56-L100

We need to ensure that both event listeners (the one of DCG and the one of MM) do not conflict.

[richardhj]

We need to ensure that both event listeners (the one of DCG and the one of MM) do not conflict.

We can give the event listener a low priority and extend the event listeners condition to:

if (!\is_int($event->getValue()) {
    return;
}

[baumannsven]

Not sure this is a BC break. In my opinion, this should only be adopted in the next major. You could use a parameter in the evaluation to control whether the date can be converted.

@discordier What do you mean?

[richardhj]

IMO saving the timestamp is the expected behavior while saving the formatted date is a bug.

I appreciate further discussion :-)

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(we then might need a ModelToLabelListener for the list view)

[baumannsven]

It's not about whether this is a bug. Hence my idea to activate the conversion in the Configuration field. Otherwise we need a database upgrade for the DCG, which is not up to the DCG. That's why I thought you could handle this properly in the next major release, if it's necessary at all. In the future DCG will use the Doctrine Abstraction Layer.

[zonky2]

It is still my opinion that the Unix timestamp is not the most elegant format for MySQL to store date and time!

MySQL has a data format with a much wider range ('1000-01-01 00:00:00:00' to '9999-12-31 23:59:59') and saves the incorrect conversions from the timestamp - see also MetaModels/core#881

(duplicate of #415 (comment))

[richardhj]

It is still my opinion that the Unix timestamp is not the most elegant format for MySQL to store date and time!

I can see the point, but from what I read, the MySQL date format ist time zone agnostic, meaning that you are not able to change the timezone in the system setting.

The second point (@discordier mentioned somewhere) is that you are not compatible with Contao.
Imagine you query a date field from the database. You will not be certain whether you fetched a PHP timestamp or a MySQL timestamp.

[discordier]

Will there still be some action on this or shall we archive this PR?