me
/
guix
Archived
1
0
Fork 0
This repository has been archived on 2024-08-07. You can view files and clone it, but cannot push or open issues/pull-requests.
guix/guix/read-print.scm

824 lines
29 KiB
Scheme
Raw Blame History

This file contains invisible Unicode characters!

This file contains invisible Unicode characters that may be processed differently from what appears below. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to reveal hidden characters.

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2021-2023 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 (guix read-print)
#:use-module (ice-9 control)
#:use-module (ice-9 match)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 vlist)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-26)
#:use-module (srfi srfi-34)
#:use-module (srfi srfi-35)
#:use-module (guix i18n)
#:use-module ((guix diagnostics)
#:select (formatted-message
&fix-hint &error-location
location))
#:export (pretty-print-with-comments
pretty-print-with-comments/splice
read-with-comments
read-with-comments/sequence
object->string*
blank?
vertical-space
vertical-space?
vertical-space-height
canonicalize-vertical-space
page-break
page-break?
<comment>
comment
comment?
comment->string
comment-margin?
canonicalize-comment))
;;; Commentary:
;;;
;;; This module provides a comment-preserving reader and a comment-preserving
;;; pretty-printer smarter than (ice-9 pretty-print).
;;;
;;; Code:
;;;
;;; Comment-preserving reader.
;;;
(define <blank>
;; The parent class for "blanks".
(make-record-type '<blank> '()
(lambda (obj port)
(format port "#<blank ~a>"
(number->string (object-address obj) 16)))
#:extensible? #t))
(define blank? (record-predicate <blank>))
(define <vertical-space>
(make-record-type '<vertical-space> '(height)
#:parent <blank>
#:extensible? #f))
(define vertical-space? (record-predicate <vertical-space>))
(define vertical-space (record-type-constructor <vertical-space>))
(define vertical-space-height (record-accessor <vertical-space> 'height))
(define canonicalize-vertical-space
(let ((unit (vertical-space 1)))
(lambda (space)
"Return a vertical space corresponding to a single blank line."
unit)))
(define <page-break>
(make-record-type '<page-break> '()
#:parent <blank>
#:extensible? #f))
(define page-break? (record-predicate <page-break>))
(define page-break
(let ((break ((record-type-constructor <page-break>))))
(lambda ()
break)))
(define <comment>
;; Comments.
(make-record-type '<comment> '(str margin?)
#:parent <blank>
#:extensible? #f))
(define comment? (record-predicate <comment>))
(define string->comment (record-type-constructor <comment>))
(define comment->string (record-accessor <comment> 'str))
(define comment-margin? (record-accessor <comment> 'margin?))
(define* (comment str #:optional margin?)
"Return a new comment made from STR. When MARGIN? is true, return a margin
comment; otherwise return a line comment. STR must start with a semicolon and
end with newline, otherwise an error is raised."
(when (or (string-null? str)
(not (eqv? #\; (string-ref str 0)))
(not (string-suffix? "\n" str)))
(raise (condition
(&message (message "invalid comment string")))))
(string->comment str margin?))
(define char-set:whitespace-sans-page-break
;; White space, excluding #\page.
(char-set-difference char-set:whitespace (char-set #\page)))
(define (space? chr)
"Return true if CHR is white space, except for page breaks."
(char-set-contains? char-set:whitespace-sans-page-break chr))
(define (read-vertical-space port)
"Read from PORT until a non-vertical-space character is met, and return a
single <vertical-space> record."
(let loop ((height 1))
(match (read-char port)
(#\newline (loop (+ 1 height)))
((? eof-object?) (vertical-space height))
((? space?) (loop height))
(chr (unread-char chr port) (vertical-space height)))))
(define (read-until-end-of-line port)
"Read white space from PORT until the end of line, included."
(let loop ()
(match (read-char port)
(#\newline #t)
((? eof-object?) #t)
((? space?) (loop))
(chr (unread-char chr port)))))
(define* (read-with-comments port #:key (blank-line? #t))
"Like 'read', but include <blank> objects when they're encountered. When
BLANK-LINE? is true, assume PORT is at the beginning of a new line."
;; Note: Instead of implementing this functionality in 'read' proper, which
;; 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 (missing-closing-paren-error)
(raise (make-compound-condition
(formatted-message (G_ "unexpected end of file"))
(condition
(&error-location
(location (match (port-filename port)
(#f #f)
(file (location file
(port-line port)
(port-column port))))))
(&fix-hint
(hint (G_ "Did you forget a closing parenthesis?")))))))
(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)
(if (pair? rest)
(let ((dotted (reverse rest)))
(set-cdr! (last-pair dotted) (car result))
dotted)
(car result)))
((x . rest) (loop (cons x result) rest)))))
(let loop ((blank-line? blank-line?)
(return (const 'unbalanced)))
(match (read-char port)
((? eof-object? eof)
eof) ;oops!
(chr
(cond ((eqv? chr #\newline)
(if blank-line?
(read-vertical-space port)
(loop #t return)))
((eqv? chr #\page)
;; Assume that a page break is on a line of its own and read
;; subsequent white space and newline.
(read-until-end-of-line port)
(page-break))
((char-set-contains? char-set:whitespace chr)
(loop blank-line? return))
((memv chr '(#\( #\[))
(let/ec return
(let liip ((lst '()))
(define item
(loop (match lst
(((? blank?) . _) #t)
(_ #f))
(lambda ()
(return (reverse/dot lst)))))
(if (eof-object? item)
(missing-closing-paren-error)
(liip (cons item lst))))))
((memv chr '(#\) #\]))
(return))
((eq? chr #\')
(list 'quote (loop #f return)))
((eq? chr #\`)
(list 'quasiquote (loop #f return)))
((eq? chr #\#)
(match (read-char port)
(#\~ (list 'gexp (loop #f return)))
(#\$ (list (match (peek-char port)
(#\@
(read-char port) ;consume
'ungexp-splicing)
(_
'ungexp))
(loop #f return)))
(#\+ (list (match (peek-char port)
(#\@
(read-char port) ;consume
'ungexp-native-splicing)
(_
'ungexp-native))
(loop #f return)))
(chr
(unread-char chr port)
(unread-char #\# port)
(read port))))
((eq? chr #\,)
(list (match (peek-char port)
(#\@
(read-char port)
'unquote-splicing)
(_
'unquote))
(loop #f return)))
((eqv? chr #\;)
(unread-char chr port)
(string->comment (read-line port 'concat)
(not blank-line?)))
(else
(unread-char chr port)
(match (read port)
((and token '#{.}#)
(if (eq? chr #\.) dot token))
(token token))))))))
(define (read-with-comments/sequence port)
"Read from PORT until the end-of-file is reached and return the list of
expressions and blanks that were read."
(let loop ((lst '())
(blank-line? #t))
(match (read-with-comments port #:blank-line? blank-line?)
((? eof-object?)
(reverse! lst))
((? blank? blank)
(loop (cons blank lst) #t))
(exp
(loop (cons exp lst) #f)))))
;;;
;;; Comment-preserving pretty-printer.
;;;
(define-syntax vhashq
(syntax-rules (quote)
((_) vlist-null)
((_ (key (quote (lst ...))) rest ...)
(vhash-consq key '(lst ...) (vhashq rest ...)))
((_ (key value) rest ...)
(vhash-consq key '((() . value)) (vhashq rest ...)))))
(define %special-forms
;; Forms that are indented specially. The number is meant to be understood
;; like Emacs' 'scheme-indent-function' symbol property. When given an
;; alist instead of a number, the alist gives "context" in which the symbol
;; is a special form; for instance, context (modify-phases) means that the
;; symbol must appear within a (modify-phases ...) expression.
(vhashq
('begin 1)
('case 2)
('cond 1)
('lambda 2)
('lambda* 2)
('match-lambda 1)
('match-lambda* 1)
('define 2)
('define* 2)
('define-public 2)
('define*-public 2)
('define-syntax 2)
('define-syntax-rule 2)
('define-module 2)
('define-gexp-compiler 2)
('define-record-type 2)
('define-record-type* 4)
('define-configuration 2)
('package/inherit 2)
('let 2)
('let* 2)
('letrec 2)
('letrec* 2)
('match 2)
('match-record 3)
('match-record-lambda 2)
('when 2)
('unless 2)
('package 1)
('origin 1)
('channel 1)
('modify-inputs 2)
('modify-phases 2)
('add-after '(((modify-phases) . 3)))
('add-before '(((modify-phases) . 3)))
('replace '(((modify-phases) . 2))) ;different from 'modify-inputs'
('parameterize 2)
('substitute* 2)
('substitute-keyword-arguments 2)
('call-with-input-file 2)
('call-with-output-file 2)
('with-output-to-file 2)
('with-input-from-file 2)
('with-directory-excursion 2)
('wrap-program 2)
('wrap-script 2)
;; (gnu system) and (gnu services).
('operating-system 1)
('bootloader-configuration 1)
('mapped-device 1)
('file-system 1)
('swap-space 1)
('user-account 1)
('user-group 1)
('setuid-program 1)
('modify-services 2)
;; (gnu home).
('home-environment 1)))
(define %newline-forms
;; List heads that must be followed by a newline. The second argument is
;; the context in which they must appear. This is similar to a special form
;; of 1, except that indent is 1 instead of 2 columns.
(vhashq
('source '(package))
('git-reference '(uri origin source))
('sha256 '(origin source package))
('arguments '(package))
('list '(arguments package))
('search-paths '(package))
('native-search-paths '(package))
('search-path-specification '())
('services '(operating-system))
('set-xorg-configuration '())
('services '(home-environment))
('home-bash-configuration '(service))
('introduction '(channel))))
(define (prefix? candidate lst)
"Return true if CANDIDATE is a prefix of LST."
(let loop ((candidate candidate)
(lst lst))
(match candidate
(() #t)
((head1 . rest1)
(match lst
(() #f)
((head2 . rest2)
(and (equal? head1 head2)
(loop rest1 rest2))))))))
(define (special-form-lead symbol context)
"If SYMBOL is a special form in the given CONTEXT, return its number of
arguments; otherwise return #f. CONTEXT is a stack of symbols lexically
surrounding SYMBOL."
(match (vhash-assq symbol %special-forms)
(#f #f)
((_ . alist)
(any (match-lambda
((prefix . level)
(and (prefix? prefix context) (- level 1))))
alist))))
(define (newline-form? symbol context)
"Return true if parenthesized expressions starting with SYMBOL must be
followed by a newline."
(let ((matches (vhash-foldq* cons '() symbol %newline-forms)))
(find (cut prefix? <> context)
matches)))
(define (escaped-string str)
"Return STR with backslashes and double quotes escaped. Everything else, in
particular newlines, is left as is."
(list->string
`(#\"
,@(string-fold-right (lambda (chr lst)
(match chr
(#\" (cons* #\\ #\" lst))
(#\\ (cons* #\\ #\\ lst))
(_ (cons chr lst))))
'()
str)
#\")))
(define %natural-whitespace-string-forms
;; When a string has one of these forms as its parent, only double quotes
;; and backslashes are escaped; newlines, tabs, etc. are left as-is.
'(synopsis description G_ N_))
(define (printed-string str context)
"Return the read syntax for STR depending on CONTEXT."
(define (preserve-newlines? str)
(and (> (string-length str) 40)
(string-index str #\newline)))
(match context
(()
(if (preserve-newlines? str)
(escaped-string str)
(object->string str)))
((head . _)
(if (or (memq head %natural-whitespace-string-forms)
(preserve-newlines? str))
(escaped-string str)
(object->string str)))))
(define (string-width str)
"Return the \"width\" of STR--i.e., the width of the longest line of STR."
(apply max (map string-length (string-split str #\newline))))
(define (canonicalize-comment comment indent)
"Canonicalize COMMENT, which is to be printed at INDENT, ensuring it has the
\"right\" number of leading semicolons."
(if (zero? indent)
comment ;leave top-level comments unchanged
(let ((line (string-trim-both
(string-trim (comment->string comment) (char-set #\;)))))
(string->comment (string-append
(if (comment-margin? comment)
";"
(if (string-null? line)
";;" ;no trailing space
";; "))
line "\n")
(comment-margin? comment)))))
(define %not-newline
(char-set-complement (char-set #\newline)))
(define (print-multi-line-comment str indent port)
"Print to PORT STR as a multi-line comment, with INDENT spaces preceding
each line except the first one (they're assumed to be already there)."
;; While 'read-with-comments' only returns one-line comments, user-provided
;; comments might span multiple lines, which is why this is necessary.
(let loop ((lst (string-tokenize str %not-newline)))
(match lst
(() #t)
((last)
(display last port)
(newline port))
((head tail ...)
(display head port)
(newline port)
(display (make-string indent #\space) port)
(loop tail)))))
(define %integer-forms
;; Forms that take an integer as their argument, where said integer should
;; be printed in base other than decimal base.
(letrec-syntax ((vhashq (syntax-rules ()
((_) vlist-null)
((_ (key value) rest ...)
(vhash-consq key value (vhashq rest ...))))))
(vhashq
('chmod 8)
('umask 8)
('mkdir 8)
('mkstemp 8)
('logand 16)
('logior 16)
('logxor 16)
('lognot 16))))
(define (integer->string integer context)
"Render INTEGER as a string using a base suitable based on CONTEXT."
(define (form-base form)
(match (vhash-assq form %integer-forms)
(#f 10)
((_ . base) base)))
(define (octal? form)
(= 8 (form-base form)))
(define base
(match context
((head . tail)
(match (form-base head)
(8 8)
(16 (if (any octal? tail) 8 16))
(10 10)))
(_ 10)))
(string-append (match base
(10 "")
(16 "#x")
(8 "#o"))
(number->string integer base)))
(define %special-non-extended-symbols
;; Special symbols that can be written without the #{...}# notation for
;; extended symbols: 1+, 1-, 123/, etc.
(make-regexp "^[0-9]+[[:graph:]]+$" regexp/icase))
(define (symbol->display-string symbol context)
"Return the most appropriate representation of SYMBOL, resorting to extended
symbol notation only when strictly necessary."
(let ((str (symbol->string symbol)))
(if (regexp-exec %special-non-extended-symbols str)
str ;no need for the #{...}# notation
(object->string symbol))))
(define* (pretty-print-with-comments port obj
#:key
(format-comment
(lambda (comment indent) comment))
(format-vertical-space identity)
(indent 0)
(max-width 78)
(long-list 5))
"Pretty-print OBJ to PORT, attempting to at most MAX-WIDTH character columns
and assuming the current column is INDENT. Comments present in OBJ are
included in the output.
Lists longer than LONG-LIST are written as one element per line. Comments are
passed through FORMAT-COMMENT before being emitted; a useful value for
FORMAT-COMMENT is 'canonicalize-comment'. Vertical space is passed through
FORMAT-VERTICAL-SPACE; a useful value of 'canonicalize-vertical-space'."
(define (list-of-lists? head tail)
;; Return true if HEAD and TAIL denote a list of lists--e.g., a list of
;; 'let' bindings.
(match head
((thing _ ...) ;proper list
(and (not (memq thing
'(quote quasiquote unquote unquote-splicing)))
(pair? tail)))
(_ #f)))
(define (starts-with-line-comment? lst)
;; Return true if LST starts with a line comment.
(match lst
((x . _) (and (comment? x) (not (comment-margin? x))))
(_ #f)))
(let loop ((indent indent)
(column indent)
(delimited? #t) ;true if comes after a delimiter
(context '()) ;list of "parent" symbols
(obj obj))
(define (print-sequence context indent column lst delimited?)
(define long?
(> (length lst) long-list))
(let print ((lst lst)
(first? #t)
(delimited? delimited?)
(column column))
(match lst
(()
column)
((item . tail)
(define newline?
;; Insert a newline if ITEM is itself a list, or if TAIL is long,
;; but only if ITEM is not the first item. Also insert a newline
;; before a keyword.
(and (or (pair? item) long?
(and (keyword? item)
(not (eq? item #:allow-other-keys))))
(not first?) (not delimited?)
(not (blank? item))))
(when newline?
(newline port)
(display (make-string indent #\space) port))
(let ((column (if newline? indent column)))
(print tail
(keyword? item) ;keep #:key value next to one another
(blank? item)
(loop indent column
(or newline? delimited?)
context
item)))))))
(define (sequence-would-protrude? indent lst)
;; Return true if elements of LST written at INDENT would protrude
;; beyond MAX-WIDTH. This is implemented as a cheap test with false
;; negatives to avoid actually rendering all of LST.
(find (match-lambda
((? string? str)
(>= (+ (string-width str) 2 indent) max-width))
((? symbol? symbol)
(>= (+ (string-width (symbol->display-string symbol context))
indent)
max-width))
((? boolean?)
(>= (+ 2 indent) max-width))
(()
(>= (+ 2 indent) max-width))
(_ ;don't know
#f))
lst))
(define (special-form? head)
(special-form-lead head context))
(match obj
((? comment? comment)
(if (comment-margin? comment)
(begin
(display " " port)
(display (comment->string (format-comment comment indent))
port))
(begin
;; When already at the beginning of a line, for example because
;; COMMENT follows a margin comment, no need to emit a newline.
(unless (= column indent)
(newline port)
(display (make-string indent #\space) port))
(print-multi-line-comment (comment->string
(format-comment comment indent))
indent port)))
(display (make-string indent #\space) port)
indent)
((? vertical-space? space)
(unless delimited? (newline port))
(let loop ((i (vertical-space-height (format-vertical-space space))))
(unless (zero? i)
(newline port)
(loop (- i 1))))
(display (make-string indent #\space) port)
indent)
((? page-break?)
(unless delimited? (newline port))
(display #\page port)
(newline port)
(display (make-string indent #\space) port)
indent)
(('quote lst)
(unless delimited? (display " " port))
(display "'" port)
(loop indent (+ column (if delimited? 1 2)) #t context lst))
(('quasiquote lst)
(unless delimited? (display " " port))
(display "`" port)
(loop indent (+ column (if delimited? 1 2)) #t context lst))
(('unquote lst)
(unless delimited? (display " " port))
(display "," port)
(loop indent (+ column (if delimited? 1 2)) #t context lst))
(('unquote-splicing lst)
(unless delimited? (display " " port))
(display ",@" port)
(loop indent (+ column (if delimited? 2 3)) #t context lst))
(('gexp lst)
(unless delimited? (display " " port))
(display "#~" port)
(loop indent (+ column (if delimited? 2 3)) #t context lst))
(('ungexp obj)
(unless delimited? (display " " port))
(display "#$" port)
(loop indent (+ column (if delimited? 2 3)) #t context obj))
(('ungexp-native obj)
(unless delimited? (display " " port))
(display "#+" port)
(loop indent (+ column (if delimited? 2 3)) #t context obj))
(('ungexp-splicing lst)
(unless delimited? (display " " port))
(display "#$@" port)
(loop indent (+ column (if delimited? 3 4)) #t context lst))
(('ungexp-native-splicing lst)
(unless delimited? (display " " port))
(display "#+@" port)
(loop indent (+ column (if delimited? 3 4)) #t context lst))
(((? special-form? head) arguments ...)
;; Special-case 'let', 'lambda', 'modify-inputs', etc. so the second
;; and following arguments are less indented.
(let* ((lead (special-form-lead head context))
(context (cons head context))
(head (symbol->display-string head (cdr context)))
(total (length arguments)))
(unless delimited? (display " " port))
(display "(" port)
(display head port)
(unless (zero? lead)
(display " " port))
;; Print the first LEAD arguments.
(let* ((indent (+ column 2
(if delimited? 0 1)))
(column (+ column 1
(if (zero? lead) 0 1)
(if delimited? 0 1)
(string-length head)))
(initial-indent column))
(define new-column
(let inner ((n lead)
(arguments (take arguments (min lead total)))
(column column))
(if (zero? n)
(begin
(newline port)
(display (make-string indent #\space) port)
indent)
(match arguments
(() column)
((head . tail)
(inner (- n 1) tail
(loop initial-indent column
(= n lead)
context
head)))))))
;; Print the remaining arguments.
(let ((column (print-sequence
context indent new-column
(drop arguments (min lead total))
#t)))
(display ")" port)
(+ column 1)))))
((head tail ...)
(let* ((overflow? (>= column max-width))
(column (if overflow?
(+ indent 1)
(+ column (if delimited? 1 2))))
(newline? (or (newline-form? head context)
(list-of-lists? head tail) ;'let' bindings
(starts-with-line-comment? tail)))
(context (cons head context)))
(if overflow?
(begin
(newline port)
(display (make-string indent #\space) port))
(unless delimited? (display " " port)))
(display "(" port)
(let* ((new-column (loop column column #t context head))
(indent (if (or (>= new-column max-width)
(not (symbol? head))
(sequence-would-protrude?
(+ new-column 1) tail)
newline?)
column
(+ new-column 1))))
(when newline?
;; Insert a newline right after HEAD.
(newline port)
(display (make-string indent #\space) port))
(let ((column
(print-sequence context indent
(if newline? indent new-column)
tail newline?)))
(display ")" port)
(+ column 1)))))
(_
(let* ((str (cond ((string? obj)
(printed-string obj context))
((integer? obj)
(integer->string obj context))
((symbol? obj)
(symbol->display-string obj context))
(else
(object->string obj))))
(len (string-width str)))
(if (and (> (+ column 1 len) max-width)
(not delimited?))
(begin
(newline port)
(display (make-string indent #\space) port)
(display str port)
(+ indent len))
(begin
(unless delimited? (display " " port))
(display str port)
(+ column (if delimited? 0 1) len))))))))
(define (object->string* obj indent . args)
"Pretty-print OBJ with INDENT columns as the initial indent. ARGS are
passed as-is to 'pretty-print-with-comments'."
(call-with-output-string
(lambda (port)
(apply pretty-print-with-comments port obj
#:indent indent
args))))
(define* (pretty-print-with-comments/splice port lst
#:rest rest)
"Write to PORT the expressions and blanks listed in LST."
(for-each (lambda (exp)
(apply pretty-print-with-comments port exp rest)
(unless (blank? exp)
(newline port)))
lst))