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style: Correctly read dots in pairs and improper lists.

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Until now dots were read as symbols.

* guix/scripts/style.scm (read-with-comments)[dot]: New variable.
[dot?, reverse/dot]: New procedures.
Use 'reverse/dot' instead of 'reverse' when reading lists.
* tests/style.scm ("read-with-comments: dot notation")
("((a . 1) (b . 2))", "(a b c . boom)"): New tests.
This commit is contained in:
Ludovic Courtès 2022-04-13 17:56:37 +02:00
parent 919cecd00b
commit c9cded0955
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GPG key ID: 090B11993D9AEBB5
2 changed files with 29 additions and 5 deletions
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25
guix/scripts/style.scm
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@ -66,8 +66,23 @@
(define (read-with-comments port)
"Like 'read', but include <comment> objects when they're encountered."
;; Note: Instead of implementing this functionality in 'read' proper, which
;; is the best approach long-term, this code is a later on top of 'read',
;; is the best approach long-term, this code is a layer on top of 'read',
;; such that we don't have to rely on a specific Guile version.
(define dot (list 'dot))
(define (dot? x) (eq? x dot))
(define (reverse/dot lst)
;; Reverse LST and make it an improper list if it contains DOT.
(let loop ((result '())
(lst lst))
(match lst
(() result)
(((? dot?) . rest)
(let ((dotted (reverse rest)))
(set-cdr! (last-pair dotted) (car result))
dotted))
((x . rest) (loop (cons x result) rest)))))
(let loop ((blank-line? #t)
(return (const 'unbalanced)))
(match (read-char port)
@ -85,7 +100,7 @@
(((? comment?) . _) #t)
(_ #f))
(lambda ()
(return (reverse lst))))
(return (reverse/dot lst))))
lst)))))
((memv chr '(#\) #\]))
(return))
@ -107,8 +122,10 @@
(not blank-line?)))
(else
(unread-char chr port)
(read port)))))))
(match (read port)
((and token '#{.}#)
(if (eq? chr #\.) dot token))
(token token))))))))
;;;
;;; Comment-preserving pretty-printer.

9
tests/style.scm
View file

@ -1,5 +1,5 @@
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2021 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2021-2022 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
@ -377,7 +377,14 @@
(list (package-inputs (@ (my-packages) my-coreutils))
(read-package-field (@ (my-packages) my-coreutils) 'inputs 4)))))
(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