Date and datetime persisted values may not conform to specified format

[guillett]

Hi folks many thanks for your great work.

Describe the bug

Date and datetime can be improperly persisted.

To Reproduce

• Add the following section to a config file

  - name: test
    label: Tests
    create: true
    folder: "content/_tests"
    fields:
      - name: title
        widget: string
      - name: date
        widget: date
        format: YYYY-MM-DD
        dateFormat: YYYY-MM-DD
        default: ''
      - name: datetime
        widget: datetime
        dateFormat: YYYY-MM-DD
        timeFormat: false
        default: ''

• Create a new entry with title and dates (pick 2020-05-06 for dates)
• Persist entry
• Check persisted data, it is OK (values in the file are 2020-05-06)
• Refresh admin site
• Update title only
• Save
• Check persisted data (values in the file are now 2020-05-07T00:00:00.000Z)

Applicable Versions:

netlify-cms-app 2.12.12 index.js:25:12
netlify-cms-core 2.26.0 bootstrap.js:83:12
netlify-cms 2.10.48 index.js:27:12

CMS configuration

https://github.com/betagouv/beta.gouv.fr/blob/master/admin/config.yml

https://github.com/betagouv/beta.gouv.fr/

Additional context

In my specific context, I found a hack to prevent that inappropriate behavior.

    var fixDateSerialization = {
      deserialize: function() {
        throw 'Not implemented' // Not used, deserialize is never called
      },
      serialize: function(value) {
        // Hack to ensure only the date part is persisted
        // Force format to YYYY-MM-DD
        return CMS.moment(value).format('YYYY-MM-DD')
      }
    }
    CMS.registerWidgetValueSerializer('date', fixDateSerialization)

[guillett]

I think this is actually a pretty complex issue.

I did not find an widget with the required logic to mimic it nor an abstraction to build on top of it. The hack I found is too outside of the packages to be easily integrated as a long term solution.

Related to

• New entries with a Date field show changed status #725

[vrabe]

It's because the value is a Date object when the frontmatter is loaded. The initial value of date / datetime widget is not formatted. If you check the preview after you refresh admin site, you'll find the date is like Thu May 07 2020 09:15:33 GMT+0000 (Coordinated Universal Time).

There may be some solutions but I haven't tested:

1. Make it parsed as a string.
   a. Use yaml 1.2
   b. Wrapped the date with quotes when saving to the file.
2. Call handleChange(value) even if value !== undefined

[erezrokah]

1. Make it parsed as a string.
   a. Use yaml 1.2
   b. Wrapped the date with quotes when saving to the file.

Your analysis is correct and thank you for posting the PR.
Your first suggestion is actually a breaking change - see #3567 so going with the second one is good 😄

[grexen]

I came across the same issue in netlify-cms 2.10.49

Sadly I can't figure out how to fix this without implementing a custom date-widget.

Could someone describe where to call the handleChange? Is it configurable for each field?