~( format directive suppresses pretty printing directives

[Zach Shaftel]

  (format nil "~<~(~A~^ ~4I~:@_~A~)~:>" '(foo bar))
yields
"foo bar"
whereas
  (format nil "~<~A~^ ~4I~:@_~A~:>" '(foo bar))
yields the expected
"FOO
    BAR"

I'm guessing this is because the case conversion stream bound by ~( is not a pretty-printing stream, so pprint-indent and pprint-newline think there's nothing for them to do.

SBCL version 2.2.8

$ uname -a
Linux bigbox 5.19.6-arch1-1 #1 SMP PREEMPT_DYNAMIC Wed, 31 Aug 2022 22:09:40 +0000 x86_64 GNU/Linux

*features* =
(:SLYNK :QUICKLISP :QUICKLISP-SUPPORT-HTTPS :ASDF3.3 :ASDF3.2 :ASDF3.1 :ASDF3
 :ASDF2 :ASDF :OS-UNIX :NON-BASE-CHARS-EXIST-P :ASDF-UNICODE :ROS.INIT :X86-64
 :GENCGC :64-BIT :ANSI-CL :COMMON-LISP :ELF :IEEE-FLOATING-POINT :LINUX
 :LITTLE-ENDIAN :PACKAGE-LOCAL-NICKNAMES :SB-CORE-COMPRESSION :SB-LDB
 :SB-PACKAGE-LOCKS :SB-THREAD :SB-UNICODE :SBCL :UNIX)