Surgically modifying an optional field (replacement for "quiet" idiom)

[philrz]

Before the quiet function was removed in #7232, it could be used in a handy idiom to surgically modify a field of a given name that might sometimes be present and sometimes absent, like this cast:

$ super -version &&
  echo '
    {"log_time":"Tue Sep  1 18:49:02 PDT 2026", "a":1}
    {"foo":"bar","a":2}' |
  super -c "put log_time:=quiet(log_time::time)" -

Version: v0.3.0-333-g25481b8bc

{log_time:2026-09-02T01:49:02Z,a:1}
{foo:"bar",a:2}

Now that quiet is gone, it's become a bit more cumbersome to express the equivalent of this.

Details

At the time this issue is being opened, super is at commit 7a03e7f. The quiet function was most recently available in commit 25481b8 as shown above.

The reason the quiet was so useful here is because without it, when the field was not present, an error("missing") appears at the location of the attempted cast.

$ super -version &&
  echo '
    {"log_time":"Tue Sep  1 18:49:02 PDT 2026", "a":1}
    {"foo":"bar","a":2}' |
  super -c "put log_time:=log_time::time" -

Version: v0.3.0-361-g7a03e7f05

{log_time:2026-09-02T01:49:02Z,a:1}
{foo:"bar",a:2,log_time:error("missing")}

The best way I've come up with to get the equivalent of what we had before uses conditional logic and spread.

$ super -version &&
  echo '
    {"log_time":"Tue Sep  1 18:49:02 PDT 2026", "a":1}
    {"foo":"bar","a":2}' |
  super -c "values has(log_time) ? {...this, log_time: log_time::time} : this" -

Version: v0.3.0-361-g7a03e7f05

{log_time:2026-09-02T01:49:02Z,a:1}
{foo:"bar",a:2}

In a pinch we could document this to encourage it as a new idiom, but it's a lot more typing for a fairly simple operation.

It's been discussed that in this era of "none" we may be able to introduce a new shorthand that covers this case in a straightforward way.