style: Move reader and printer to (guix read-print).

* guix/scripts/style.scm (<comment>, read-with-comments)
(vhashq, %special-forms, %newline-forms, prefix?)
(special-form-lead, newline-form?, escaped-string)
(string-width, canonicalize-comment, pretty-print-with-comments)
(object->string*): Move to...
* guix/read-print.scm: ... here.  New file.
* guix/scripts/import.scm: Adjust accordingly.
* tests/style.scm: Move 'test-pretty-print' and tests to...
* tests/read-print.scm: ... here.  New file.
* Makefile.am (MODULES): Add 'guix/read-print.scm'.
(SCM_TESTS): Add 'tests/read-print.scm'.

tests/read-print.scm

@@ -0,0 +1,209 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2021-2022 Ludovic Courtès <ludo@gnu.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (tests-style)
+  #:use-module (guix read-print)
+  #:use-module (guix gexp)                        ;for the reader extensions
+  #:use-module (srfi srfi-64))
+
+(define-syntax-rule (test-pretty-print str args ...)
+  "Test equality after a round-trip where STR is passed to
+'read-with-comments' and the resulting sexp is then passed to
+'pretty-print-with-comments'."
+  (test-equal str
+    (call-with-output-string
+      (lambda (port)
+        (let ((exp (call-with-input-string str
+                     read-with-comments)))
+         (pretty-print-with-comments port exp args ...))))))
+
+
+(test-begin "read-print")
+
+(test-equal "read-with-comments: dot notation"
+  (cons 'a 'b)
+  (call-with-input-string "(a . b)"
+    read-with-comments))
+
+(test-pretty-print "(list 1 2 3 4)")
+(test-pretty-print "((a . 1) (b . 2))")
+(test-pretty-print "(a b c . boom)")
+(test-pretty-print "(list 1
+                          2
+                          3
+                          4)"
+                   #:long-list 3
+                   #:indent 20)
+(test-pretty-print "\
+(list abc
+      def)"
+                   #:max-width 11)
+(test-pretty-print "\
+(#:foo
+ #:bar)"
+                   #:max-width 10)
+
+(test-pretty-print "\
+(#:first 1
+ #:second 2
+ #:third 3)")
+
+(test-pretty-print "\
+((x
+  1)
+ (y
+  2)
+ (z
+  3))"
+                   #:max-width 3)
+
+(test-pretty-print "\
+(let ((x 1)
+      (y 2)
+      (z 3)
+      (p 4))
+  (+ x y))"
+                   #:max-width 11)
+
+(test-pretty-print "\
+(lambda (x y)
+  ;; This is a procedure.
+  (let ((z (+ x y)))
+    (* z z)))")
+
+(test-pretty-print "\
+#~(string-append #$coreutils \"/bin/uname\")")
+
+(test-pretty-print "\
+(package
+  (inherit coreutils)
+  (version \"42\"))")
+
+(test-pretty-print "\
+(modify-phases %standard-phases
+  (add-after 'unpack 'post-unpack
+    (lambda _
+      #t))
+  (add-before 'check 'pre-check
+    (lambda* (#:key inputs #:allow-other-keys)
+      do things ...)))")
+
+(test-pretty-print "\
+(#:phases (modify-phases sdfsdf
+            (add-before 'x 'y
+              (lambda _
+                xyz))))")
+
+(test-pretty-print "\
+(description \"abcdefghijkl
+mnopqrstuvwxyz.\")"
+                   #:max-width 30)
+
+(test-pretty-print "\
+(description
+ \"abcdefghijkl
+mnopqrstuvwxyz.\")"
+                   #:max-width 12)
+
+(test-pretty-print "\
+(description
+ \"abcdefghijklmnopqrstuvwxyz\")"
+                   #:max-width 33)
+
+(test-pretty-print "\
+(modify-phases %standard-phases
+  (replace 'build
+    ;; Nicely indented in 'modify-phases' context.
+    (lambda _
+      #t)))")
+
+(test-pretty-print "\
+(modify-inputs inputs
+  ;; Regular indentation for 'replace' here.
+  (replace \"gmp\" gmp))")
+
+(test-pretty-print "\
+(package
+  ;; Here 'sha256', 'base32', and 'arguments' must be
+  ;; immediately followed by a newline.
+  (source (origin
+            (method url-fetch)
+            (sha256
+             (base32
+              \"not a real base32 string\"))))
+  (arguments
+   '(#:phases %standard-phases
+     #:tests? #f)))")
+
+;; '#:key value' is kept on the same line.
+(test-pretty-print "\
+(package
+  (name \"keyword-value-same-line\")
+  (arguments
+   (list #:phases #~(modify-phases %standard-phases
+                      (add-before 'x 'y
+                        (lambda* (#:key inputs #:allow-other-keys)
+                          (foo bar baz))))
+         #:make-flags #~'(\"ANSWER=42\")
+         #:tests? #f)))")
+
+(test-pretty-print "\
+(let ((x 1)
+      (y 2)
+      (z (let* ((a 3)
+                (b 4))
+           (+ a b))))
+  (list x y z))")
+
+(test-pretty-print "\
+(substitute-keyword-arguments (package-arguments x)
+  ((#:phases phases)
+   `(modify-phases ,phases
+      (add-before 'build 'do-things
+        (lambda _
+          #t))))
+  ((#:configure-flags flags)
+   `(cons \"--without-any-problem\"
+          ,flags)))")
+
+(test-equal "pretty-print-with-comments, canonicalize-comment"
+  "\
+(list abc
+      ;; Not a margin comment.
+      ;; Ditto.
+      ;;
+      ;; There's a blank line above.
+      def ;margin comment
+      ghi)"
+  (let ((sexp (call-with-input-string
+                  "\
+(list abc
+  ;Not a margin comment.
+  ;;;  Ditto.
+  ;;;;;
+  ; There's a blank line above.
+  def  ;; margin comment
+  ghi)"
+                read-with-comments)))
+    (call-with-output-string
+      (lambda (port)
+        (pretty-print-with-comments port sexp
+                                    #:format-comment
+                                    canonicalize-comment)))))
+
+(test-end)