Adventures in Validating Email Addresses with Clojure

testdata.txt

admin@mailserver1
niceandsimple@example.com
very.common@example.com
a.little.lengthy.but.fine@dept.example.com
disposable.style.email.with+symbol@example.com

postbox@com

user@[192.168.2.1]
user@[IPv6:2001:db8:1ff::a0b:dbd0]

"much.more unusual"@example.com
" "@example.org
"very.unusual.@.unusual.com"@example.com

"very.(),:;<>[]\".VERY.\"very@\\ \"very\".unusual"@strange.example.com
!#$%&'*+-/=?^_`{}|~@example.org
"()<>[]:,;@\\\"!#$%&'*+-/=?^_`{}| ~.a"@example.org

(comment)user1.(comment)@(comment)example.com(comment)

validate_email.clj

;; Version 1

(ns validate-email
  (:require [clojure.test :refer :all]))

(defn email-valid? [s] (not (nil? (re-matches #"[a-z\.\+]+@[a-z\.]+" s))))

(deftest filters-invalid-email-addresses
  (let [invalid-emails ["Abc.example.com"
                        "A@b@c@example.com"
                        "a\"b(c)d,e:f;g<h>i[j\\k]l@example.com"
                        "just\"not\"right@example.com"
                        "this is\"not\\allowed@example.com"
                        "this\\ still\\\"not\\\\allowed@example.com"
                        "not(this)either@example.com"]]
    (is (every? (complement email-valid?) invalid-emails))))

;; Version 2

(ns validate-email
  (:require [clojure.test :refer :all]
            [instaparse.core :as insta]))

(def parse-email-address
  (insta/parser "ADDRESS = LOCAL <'@'> DOMAIN

                LOCAL = COMMENT? LOCALVALUE COMMENT?
                LOCALVALUE = (LOCALSANDQUOTES DOT)* LOCALSANDQUOTES
                <LOCALSANDQUOTES> = (LOCALS | QUOTEDSTRING)
                <LOCALS> = (LETTER | NUMBER | LOCALSYMBOL)+
                QUOTEDSTRING = <'\"'> (LETTER | NUMBER | LOCALSYMBOL | DOT | QUOTEDSYMBOL)* <'\"'>
                <LOCALSYMBOL> = '!'|'#'|'$'|'%'|'&'|'*'|'+'|'-'|'/'|'?'|'^'|'_'|'`'|'{'|'}'|'~'|'='|'|'|\"'\"
                <QUOTEDSYMBOL> = ' '|'('|')'|','|':'|';'|'<'|'>'|'@'|'['|']'|QUOTEDESCAPEDSYMBOL
                QUOTEDESCAPEDSYMBOL = <'\\\\'> ('\\\\' | '\"' | LETTER | NUMBER | HEXENTITY | ' ' | '\0')

                DOMAIN = COMMENT? DOMAINVALUE COMMENT?
                DOMAINVALUE = (IPADDRESS | HOSTNAME)
                IPADDRESS = <'['> (IP4ADDRESS|IP6ADDRESS|DOMAINLITERAL) <']'>
                IP4ADDRESS = NUMBER NUMBER? NUMBER? '.' NUMBER NUMBER? NUMBER? '.' NUMBER NUMBER? NUMBER? '.' NUMBER NUMBER? NUMBER?
                IP6ADDRESS = <'IPv6:'> (HEX | ':')+
                DOMAINLITERAL = DOMAINLITERALSYMBOL+
                DOMAINLITERALSYMBOL = LETTER|NUMBER|'!'|'\"'|'#'|'$'|'%'|'&'|\"'\"|'('|')'|'*'|'+'|','|'-'|'.'|'/'|':'|';'|'<'|'='|'>'|'?'|'@'|'^'|'_'|'`'|'{'|'|'|'}'|'~'
                HOSTNAME = (LABEL DOT)* LABEL
                LABEL = &(LETTER | NUMBER) (LETTER | NUMBER | '-')* (LETTER | NUMBER)

                <DOT> = '.'
                COMMENT = <'('> (LETTER | COMMENTESCAPEDSYMBOL | HEXENTITY | COMMENT)* <')'>
                <COMMENTESCAPEDSYMBOL> = '\\\\' ('\\\\' | '\"' | ')')
                HEXENTITY = <'&'> <'#'> <'x'> HEX+ <';'>
                <HEX> = NUMBER|'a'|'b'|'c'|'d'|'e'|'f'|'A'|'B'|'C'|'D'|'E'|'F'
                <NUMBER> = '0'|'1'|'2'|'3'|'4'|'5'|'6'|'7'|'8'|'9'
                <LETTER> = 'a'|'b'|'c'|'d'|'e'|'f'|'g'|'h'|'i'|'j'|'k'|'l'|'m'|'n'|'o'|'p'|'q'|'r'|'s'|'t'|'u'|'v'|'w'|'x'|'y'|'z'|
                           'A'|'B'|'C'|'D'|'E'|'F'|'G'|'H'|'I'|'J'|'K'|'L'|'M'|'N'|'O'|'P'|'Q'|'R'|'S'|'T'|'U'|'V'|'W'|'X'|'Y'|'Z'
                "))

(defn email-valid? [e]
  (not (insta/failure? (parse-email-address e))))

(deftest filters-invalid-email-addresses
  (let [invalid-emails ["Abc.example.com"
                        "A@b@c@example.com"
                        "a\"b(c)d,e:f;g<h>i[j\\k]l@example.com"
                        "just\"not\"right@example.com"
                        "this is\"not\\allowed@example.com"
                        "this\\ still\\\"not\\\\allowed@example.com"
                        "not(this)either@example.com"]]
    (is (every? (complement email-valid?) invalid-emails))))

(deftest validates-valid-email-addresses
  (let [valid-emails ["admin@mailserver1"
                      "niceandsimple@example.com"
                      "very.common@example.com"
                      "disposable.style.email.with+symbol@example.com"
                      "postbox@com"
                      "user@[192.168.2.1]"
                      "user@[IPv6:2001:db8:1ff::a0b:dbd0]"
                      "\"much.more unusual\"@example.com"
                      "\"very.unusual.@.unusual.com\"@example.com"
                      "\"very.(),:;<>[]\\\".VERY.\\\"very@\\\\ \\\"very\\\".unusual\"@strange.example.com"
                      "!#$%&'*+-/=?^_`{}|~@example.org"
                      "\"()<>[]:,;@\\\\\\\"!#$%&'*+-/=?^_`{}| ~.a\"@example.org"
                      "\" \"@example.org"
                      "(comment)john.smith(comment)@(comment)example.com(comment)"]]
    (is (every? email-valid? valid-emails))))