Panic in log package about kit HOT 4 CLOSED

@ChrisHines what do you think?

 if len(keyvals)%2 != 0 {
-    panic("bad keyvals")
+    keyvals = append(keyvals, "(MISSING)")
 }

from kit.

I don't have any preferences here. I think (MISSING) is easier to spot when browsing logs than empty string or nil.
👍

from kit.

+1

from kit.

I agree that we should remove these panics.

In logfmt.MarshalKeyvals I appended nil in this scenario. That package logs a nil value the same as JSON (i.e. "null").

At the slightly higher level of abstraction here in the log package it seems reasonable to provide a more helpful indicator. I would also like to make it easy for applications to control how a missing value is ultimately handled, so I don't like a "magic" string.

I propose adding an exported error variable that is appended and can be checked by a downstream logger if a different behavior is desired.

var ErrMissingValue interface{} = errors.New("(MISSING)")

from kit.