The string type does not automatically add spaces.

[FH0]

a := "a"
zap.S().Debug(a, a)
fmt.Println(a, a)

zap will print "aa"
fmt will print "a a"

[johnaoss]

@FH0 The SugaredLogger.Debug documentation states that Debug uses fmt.Sprint internally for creating strings.

The behaviour of fmt.Sprint is:

Sprint formats using the default formats for its operands and returns the resulting string. Spaces are added between operands when neither is a string.

Whereas you show fmt.Println which says:

Println formats using the default formats for its operands and writes to standard output. Spaces are always added between operands and a newline is appended. It returns the number of bytes written and any write error encountered.