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;;; peg-tests.el --- Tests of PEG parsers -*- lexical-binding: t; -*-
;; Copyright (C) 2008-2025 Free Software Foundation, Inc.
;; This program 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.
;; This program 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 this program. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Tests and examples, that used to live in peg.el wrapped inside an `eval'.
;;; Code:
(require 'peg)
(require 'ert)
;;; Tests:
(defmacro peg-parse-string (pex string &optional noerror)
"Parse STRING according to PEX.
If NOERROR is non-nil, push nil resp. t if the parse failed
resp. succeeded instead of signaling an error."
(declare (indent 1))
(let ((oldstyle (consp (car-safe pex)))) ;PEX is really a list of rules.
`(with-temp-buffer
(insert ,string)
(goto-char (point-min))
,(if oldstyle
`(with-peg-rules ,pex
(peg-run (peg ,(caar pex))
,(unless noerror '#'peg-signal-failure)))
`(peg-run (peg ,pex)
,(unless noerror '#'peg-signal-failure))))))
(define-peg-rule peg-test-natural ()
[0-9] (* [0-9]))
(ert-deftest peg-test ()
(should (peg-parse-string peg-test-natural "99 bottles" t))
(should (peg-parse-string ((s "a")) "a" t))
(should (not (peg-parse-string ((s "a")) "b" t)))
(should (peg-parse-string ((s (not "a"))) "b" t))
(should (not (peg-parse-string ((s (not "a"))) "a" t)))
(should (peg-parse-string ((s (if "a"))) "a" t))
(should (not (peg-parse-string ((s (if "a"))) "b" t)))
(should (peg-parse-string ((s "ab")) "ab" t))
(should (not (peg-parse-string ((s "ab")) "ba" t)))
(should (not (peg-parse-string ((s "ab")) "a" t)))
(should (peg-parse-string ((s (range ?0 ?9))) "0" t))
(should (not (peg-parse-string ((s (range ?0 ?9))) "a" t)))
(should (peg-parse-string ((s [0-9])) "0" t))
(should (not (peg-parse-string ((s [0-9])) "a" t)))
(should (not (peg-parse-string ((s [0-9])) "" t)))
(should (peg-parse-string ((s (any))) "0" t))
(should (not (peg-parse-string ((s (any))) "" t)))
(should (peg-parse-string ((s (eob))) "" t))
(should (peg-parse-string ((s (not (eob)))) "a" t))
(should (peg-parse-string ((s (or "a" "b"))) "a" t))
(should (peg-parse-string ((s (or "a" "b"))) "b" t))
(should (not (peg-parse-string ((s (or "a" "b"))) "c" t)))
(should (peg-parse-string (and "a" "b") "ab" t))
(should (peg-parse-string ((s (and "a" "b"))) "abc" t))
(should (not (peg-parse-string (and "a" "b") "ba" t)))
(should (peg-parse-string ((s (and "a" "b" "c"))) "abc" t))
(should (peg-parse-string ((s (* "a") "b" (eob))) "b" t))
(should (peg-parse-string ((s (* "a") "b" (eob))) "ab" t))
(should (peg-parse-string ((s (* "a") "b" (eob))) "aaab" t))
(should (not (peg-parse-string ((s (* "a") "b" (eob))) "abc" t)))
(should (peg-parse-string ((s "")) "abc" t))
(should (peg-parse-string ((s "" (eob))) "" t))
(should (peg-parse-string ((s (opt "a") "b")) "abc" t))
(should (peg-parse-string ((s (opt "a") "b")) "bc" t))
(should (not (peg-parse-string ((s (or))) "ab" t)))
(should (peg-parse-string ((s (and))) "ab" t))
(should (peg-parse-string ((s (and))) "" t))
(should (peg-parse-string ((s ["^"])) "^" t))
(should (peg-parse-string ((s ["^a"])) "a" t))
(should (peg-parse-string ["-"] "-" t))
(should (peg-parse-string ((s ["]-"])) "]" t))
(should (peg-parse-string ((s ["^]"])) "^" t))
(should (peg-parse-string ((s [alpha])) "z" t))
(should (not (peg-parse-string ((s [alpha])) "0" t)))
(should (not (peg-parse-string ((s [alpha])) "" t)))
(should (not (peg-parse-string ((s ["][:alpha:]"])) "z" t)))
(should (peg-parse-string ((s (bob))) "" t))
(should (peg-parse-string ((s (bos))) "x" t))
(should (not (peg-parse-string ((s (bos))) " x" t)))
(should (peg-parse-string ((s "x" (eos))) "x" t))
(should (peg-parse-string ((s (syntax-class whitespace))) " " t))
(should (peg-parse-string ((s (= "foo"))) "foo" t))
(should (let ((f "foo")) (peg-parse-string ((s (= f))) "foo" t)))
(should (not (peg-parse-string ((s (= "foo"))) "xfoo" t)))
(should (equal (peg-parse-string ((s `(-- 1 2))) "") '(2 1)))
(should (equal (peg-parse-string ((s `(-- 1 2) `(a b -- a b))) "") '(2 1)))
(should (equal (peg-parse-string ((s (or (and (any) s)
(substring [0-9]))))
"ab0cd1ef2gh")
'("2")))
;; The PEG rule `doesntexist' doesn't exist, which will cause a byte-compiler
;; warning, but not an error at run time because the rule is not actually
;; used in this particular case.
(let* ((testfun '(lambda ()
(peg-parse-string ((s (substring (or "a" doesntexist)))
;; Unused left-recursive rule, should
;; cause a byte-compiler warning.
(r (* "a") r))
"af")))
(compiledfun
(progn
(with-current-buffer (get-buffer-create "*Compile-Log*")
(let ((inhibit-read-only t)) (erase-buffer)))
(let ((lexical-binding t)) (byte-compile testfun)))))
(with-current-buffer (get-buffer-create "*Compile-Log*")
(goto-char (point-min))
(should
;; FIXME: The byte-compiler emits "not known to be defined"
;; warnings when compiling a file but not from `byte-compile'.
;; Instead, we have to dig it out of the mess it leaves behind. 🙂
(or (assq 'peg-rule\ doesntexist byte-compile-unresolved-functions)
(should (re-search-forward
"peg-rule.? doesntexist.*not known to be defined" nil t))))
(goto-char (point-min))
(should (re-search-forward "left recursion.*r -> r" nil t)))
(should (equal (funcall compiledfun) '("a"))))
(should (equal (peg-parse-string ((s (list x y))
(x `(-- 1))
(y `(-- 2)))
"")
'((1 2))))
(should (equal (peg-parse-string ((s (list (* x)))
(x "" `(-- 'x)))
"xxx")
;; The empty loop body should be matched once!
'((x))))
(should (equal (peg-parse-string ((s (list (* x)))
(x "x" `(-- 'x)))
"xxx")
'((x x x))))
(should (equal (peg-parse-string ((s (region (* x)))
(x "x" `(-- 'x)))
"xxx")
;; FIXME: Since string positions start at 0, this should
;; really be '(3 x x x 0) !!
'(4 x x x 1)))
(should (equal (peg-parse-string ((s (region (list (* x))))
(x "x" `(-- 'x 'y)))
"xxx")
'(4 (x y x y x y) 1)))
(should (equal (with-temp-buffer
(save-excursion (insert "abcdef"))
(list
(peg-run (peg "a"
(replace "bc" "x")
(replace "de" "y")
"f"))
(buffer-string)))
'(t "axyf")))
(with-temp-buffer
(insert "toro")
(goto-char (point-min))
(should (peg-run (peg "to")))
(should-not (peg-run (peg "to")))
(should (peg-run (peg "ro")))
(should (eobp)))
(with-temp-buffer
(insert " ")
(goto-char (point-min))
(peg-run (peg (+ (syntax-class whitespace))))
(should (eobp)))
)
(define-peg-ruleset peg-test-myrules
(sign () (or "+" "-" ""))
(digit () [0-9])
(nat () digit (* digit))
(int () sign digit (* digit))
(float () int "." nat))
(ert-deftest peg-test-ruleset ()
(with-peg-rules
(peg-test-myrules
(complex float "+i" float))
(should (peg-parse-string nat "123" t))
(should (not (peg-parse-string nat "home" t)))))
;;; Examples:
;; peg-ex-recognize-int recognizes integers. An integer begins with a
;; optional sign, then follows one or more digits. Digits are all
;; characters from 0 to 9.
;;
;; Notes:
;; 1) "" matches the empty sequence, i.e. matches without consuming
;; input.
;; 2) [0-9] is the character range from 0 to 9. This can also be
;; written as (range ?0 ?9). Note that 0-9 is a symbol.
(defun peg-ex-recognize-int ()
(with-peg-rules ((number sign digit (* digit))
(sign (or "+" "-" ""))
(digit [0-9]))
(peg-run (peg number))))
;; peg-ex-parse-int recognizes integers and computes the corresponding
;; value. The grammar is the same as for `peg-ex-recognize-int'
;; augmented with parsing actions. Unfortunately, the actions add
;; quite a bit of clutter.
;;
;; The actions for the sign rule push -1 on the stack for a minus sign
;; and 1 for plus or no sign.
;;
;; The action for the digit rule pushes the value for a single digit.
;;
;; The action `(a b -- (+ (* a 10) b)), takes two items from the stack
;; and pushes the first digit times 10 added to the second digit.
;;
;; The action `(sign val -- (* sign val)), multiplies val with the
;; sign (1 or -1).
(defun peg-ex-parse-int ()
(with-peg-rules ((number sign digit (* digit
`(a b -- (+ (* a 10) b)))
`(sign val -- (* sign val)))
(sign (or (and "+" `(-- 1))
(and "-" `(-- -1))
(and "" `(-- 1))))
(digit [0-9] `(-- (- (char-before) ?0))))
(peg-run (peg number))))
;; Put point after the ) and press C-x C-e
;; (peg-ex-parse-int)-234234
;; Parse arithmetic expressions and compute the result as side effect.
(defun peg-ex-arith ()
(peg-parse
(expr _ sum eol)
(sum product (* (or (and "+" _ product `(a b -- (+ a b)))
(and "-" _ product `(a b -- (- a b))))))
(product value (* (or (and "*" _ value `(a b -- (* a b)))
(and "/" _ value `(a b -- (/ a b))))))
(value (or (and (substring number) `(string -- (string-to-number string)))
(and "(" _ sum ")" _)))
(number (+ [0-9]) _)
(_ (* [" \t"]))
(eol (or "\n" "\r\n" "\r"))))
;; (peg-ex-arith) 1 + 2 * 3 * (4 + 5)
;; (peg-ex-arith) 1 + 2 ^ 3 * (4 + 5) ; fails to parse
;; Parse URI according to RFC 2396.
(defun peg-ex-uri ()
(peg-parse
(URI-reference (or absoluteURI relativeURI)
(or (and "#" (substring fragment))
`(-- nil))
`(scheme user host port path query fragment --
(list :scheme scheme :user user
:host host :port port
:path path :query query
:fragment fragment)))
(absoluteURI (substring scheme) ":" (or hier-part opaque-part))
(hier-part ;(-- user host port path query)
(or net-path
(and `(-- nil nil nil)
abs-path))
(or (and "?" (substring query))
`(-- nil)))
(net-path "//" authority (or abs-path `(-- nil)))
(abs-path "/" path-segments)
(path-segments segment (list (* "/" segment)) `(s l -- (cons s l)))
(segment (substring (* pchar) (* ";" param)))
(param (* pchar))
(pchar (or unreserved escaped [":@&=+$,"]))
(query (* uric))
(fragment (* uric))
(relativeURI (or net-path abs-path rel-path) (opt "?" query))
(rel-path rel-segment (opt abs-path))
(rel-segment (+ unreserved escaped [";@&=+$,"]))
(authority (or server reg-name))
(server (or (and (or (and (substring userinfo) "@")
`(-- nil))
hostport)
`(-- nil nil nil)))
(userinfo (* (or unreserved escaped [";:&=+$,"])))
(hostport (substring host) (or (and ":" (substring port))
`(-- nil)))
(host (or hostname ipv4address))
(hostname (* domainlabel ".") toplabel (opt "."))
(domainlabel alphanum
(opt (* (or alphanum "-") (if alphanum))
alphanum))
(toplabel alpha
(* (or alphanum "-") (if alphanum))
alphanum)
(ipv4address (+ digit) "." (+ digit) "." (+ digit) "." (+ digit))
(port (* digit))
(scheme alpha (* (or alpha digit ["+-."])))
(reg-name (or unreserved escaped ["$,;:@&=+"]))
(opaque-part uric-no-slash (* uric))
(uric (or reserved unreserved escaped))
(uric-no-slash (or unreserved escaped [";?:@&=+$,"]))
(reserved (set ";/?:@&=+$,"))
(unreserved (or alphanum mark))
(escaped "%" hex hex)
(hex (or digit [A-F] [a-f]))
(mark (set "-_.!~*'()"))
(alphanum (or alpha digit))
(alpha (or lowalpha upalpha))
(lowalpha [a-z])
(upalpha [A-Z])
(digit [0-9])))
;; (peg-ex-uri)http://luser@www.foo.com:8080/bar/baz.html?x=1#foo
;; (peg-ex-uri)file:/bar/baz.html?foo=df#x
;; Split STRING where SEPARATOR occurs.
(defun peg-ex-split (string separator)
(peg-parse-string ((s (list (* (* sep) elt)))
(elt (substring (+ (not sep) (any))))
(sep (= separator)))
string))
;; (peg-ex-split "-abc-cd-" "-")
;; Parse a lisp style Sexp.
;; [To keep the example short, ' and . are handled as ordinary symbol.]
(defun peg-ex-lisp ()
(peg-parse
(sexp _ (or string list number symbol))
(_ (* (or [" \n\t"] comment)))
(comment ";" (* (not (or "\n" (eob))) (any)))
(string "\"" (substring (* (not "\"") (any))) "\"")
(number (substring (opt (set "+-")) (+ digit))
(if terminating)
`(string -- (string-to-number string)))
(symbol (substring (and symchar (* (not terminating) symchar)))
`(s -- (intern s)))
(symchar [a-z A-Z 0-9 "-;!#%&'*+,./:;<=>?@[]^_`{|}~"])
(list "(" `(-- (cons nil nil)) `(hd -- hd hd)
(* sexp `(tl e -- (setcdr tl (list e))))
_ ")" `(hd _tl -- (cdr hd)))
(digit [0-9])
(terminating (or (set " \n\t();\"'") (eob)))))
;; (peg-ex-lisp)
;; We try to detect left recursion and report it as error.
(defun peg-ex-left-recursion ()
(eval '(peg-parse (exp (or term
(and exp "+" exp)))
(term (or digit
(and term "*" term)))
(digit [0-9]))
t))
(defun peg-ex-infinite-loop ()
(eval '(peg-parse (exp (* (or "x"
"y"
(action (foo))))))
t))
;; Some efficiency problems:
;; Find the last digit in a string.
;; Recursive definition with excessive stack usage.
(defun peg-ex-last-digit (string)
(peg-parse-string ((s (or (and (any) s)
(substring [0-9]))))
string))
;; (peg-ex-last-digit "ab0cd1ef2gh")
;; (peg-ex-last-digit (make-string 50 ?-))
;; (peg-ex-last-digit (make-string 1000 ?-))
;; Find the last digit without recursion. Doesn't run out of stack,
;; but probably still too inefficient for large inputs.
(defun peg-ex-last-digit2 (string)
(peg-parse-string ((s `(-- nil)
(+ (* (not digit) (any))
(substring digit)
`(_d1 d2 -- d2)))
(digit [0-9]))
string))
;; (peg-ex-last-digit2 "ab0cd1ef2gh")
;; (peg-ex-last-digit2 (concat (make-string 500000 ?-) "8a9b"))
;; (peg-ex-last-digit2 (make-string 500000 ?-))
;; (peg-ex-last-digit2 (make-string 500000 ?5))
(provide 'peg-tests)
;;; peg-tests.el ends here
|
