I guess the infobox or the article calls {{#property:programming language}} or {{#statements:programming language}} to retrieve the values of the Wikidata property P277.
However, the English label was changed today to "programmed in". It can be fixed by either changing the code to {{#property:P277}} (the property identifier cannot change, so this is the most stable) or {{#property:programmed in}}, or reverting the change if it's not appropriate.

In T322178#8361883, @matej_suchanek wrote:

I guess the infobox or the article calls {{#property:programming language}} or {{#statements:programming language}} to retrieve the values of the Wikidata property P277.
However, the English label was changed today to "programmed in". It can be fixed by either changing the code to {{#property:P277}} (the property identifier cannot change, so this is the most stable) or {{#property:programmed in}}, or reverting the change if it's not appropriate.

Thank you for nailing down the cause.
Any idea why the visual editor still prints the correct infobox information?

Any idea why the visual editor still prints the correct infobox information?

When I open the article using the visual editor, the browser does the following request:
GET https://en.wikipedia.org/api/rest_v1/page/html/Gitea/1119320629?redirect=false&stash=true
The response does not contain the error. It seems there is a cache that isn't invalidated by that side effect (I don't know if and when it expires).

The evidence for the above may be the "## days ago" in the "Stable release" field. When I started editing, I got "17 days ago" and no error. When I make a (dummy) change to the infobox, it skips to "19 days ago" and shows the error. Maybe it's suboptimal.

Following up on this. It seems like editors took it upon themselves and manually corrected the issue where they saw it on articles. This is a bandaid.

Another error has now happened on the article for vue.js in the "Stable release" infobox field.

Obviously, {{start date and age|{{wikidata|qualifier|P548=Q2804309|P348|P577}}}} is responsible for that. The inner call {{wikidata|...}} returns a list of all "publication date" qualifiers for "software version identifier", although only the one for "3.2.42" is desirable.

After some debugging, I noticed that the preferred statement for "3.2.42" is missing "version type: stable version", which the template expects (P548=Q2804309).

In T322178#8449823, @Aklapper wrote:

Hi, this seems to be an on-wiki content problem. These are not tracked in Phabricator.

It is not. Please reread the above messages from other users a little more carefully. Particularly

In T322178#8361883, @matej_suchanek wrote:

I guess the infobox or the article calls {{#property:programming language}} or {{#statements:programming language}} to retrieve the values of the Wikidata property P277.
However, the English label was changed today to "programmed in". It can be fixed by either changing the code to {{#property:P277}} (the property identifier cannot change, so this is the most stable) or {{#property:programmed in}}, or reverting the change if it's not appropriate.

Here's another I just found today.

These aren't issues that concern editors or are caused at the editor-level but due to changes in property identifiers.

Please let me know your thoughts @Aklapper , I will reopen this eventually after a bit.

In T322178#8473081, @Mehrpw wrote:

In T322178#8449823, @Aklapper wrote:

Hi, this seems to be an on-wiki content problem. These are not tracked in Phabricator.

It is not. Please reread the above messages from other users a little more carefully.

Actually, it is something that can be fixed by editing a page (whether it's the article, the template, the item, or the property). Showing an error message when invalid input is provided is technically correct and expected behavior.

For the initial problem, T101107 (T89661) is a possible solution, but it has never been implemented.