Become RFC 5322-compliant

index.d.ts

@@ -7,6 +7,20 @@ export interface Options {
 	@default false
 	*/
 	readonly exact?: boolean;
+
+	/**
+	Allow emails with a domain that doesn't have a dot, such as `user@localhost` or `user@internal`.
+
+	@default true
+	*/
+	readonly allowSingleLabelDomain?: boolean;
+
+	/**
+	Allow the ampersand HTML entity `&` to correspond to an ampersand `&` in the email address.
+
+	@default false
+	*/
+	readonly allowAmpersandEntity?: boolean;
 }
 
 /**

index.js

@@ -1,5 +1,44 @@
-const regex = '[^\\.\\s@:](?:[^\\s@:]*[^\\s@:\\.])?@[^\\.\\s@]+(?:\\.[^\\.\\s@]+)*';
+export default function emailRegex(options) {
+	options = {
+		exact: false,
+		allowSingleLabelDomain: true,
+		allowAmpersandEntity: false,
+		...options
+	};
 
-export default function emailRegex({exact} = {}) {
-	return exact ? new RegExp(`^${regex}$`) : new RegExp(regex, 'g');
+	// RFC 5322 (https://datatracker.ietf.org/doc/html/rfc5322)
+	const alpha = '[A-Za-z]';
+	const digit = String.raw`\d`;
+	const atext = String.raw`(?:${alpha}|${digit}|[!#$%&'*+\-/=?^_\`{|}~]${options.allowAmpersandEntity ? '|&' : ''})`;
+	const dotAtomText = String.raw`(?:${atext}+(?:\.${atext}+)+)`;
+	const dotAtom = `${dotAtomText}`;
+	const dquote = '"';
+	const sp = ' ';
+	const htab = String.raw`\u0009`;
+	const wsp = `(?:${sp}|${htab})`;
+	const cr = String.raw`\u000D`;
+	const lf = String.raw`\u000A`;
+	const crlf = `(?:${cr}${lf})`;
+	const obsFws = `(?:${wsp}+(?:${crlf}${wsp}+)*)`;
+	const fws = `(?:(?:(?:${wsp}*${crlf})?${wsp}+)|${obsFws})`;
+	const obsNoWsCtl = String.raw`(?:[\u0001-\u0008]|\u000B|\u000C|[\u000E-\u001F]|\u007F)`;
+	const obsQtext = `${obsNoWsCtl}`;
+	const qtext = String.raw`(?:!|[\u0023-\u005B]|[\u005D-\u007E]|${obsQtext})`;
+	const vchar = String.raw`[\u0021-\u007E]`;
+	const obsQp = String.raw`(?:\\(?:\u0000|${obsNoWsCtl}|${lf}|${cr}))`;
+	const quotedPair = String.raw`(?:(?:\\(?:${vchar}|${wsp}))|${obsQp})`;
+	const qcontent = `(?:${qtext}|${quotedPair})`;
+	const quotedString = `(?:${dquote}(?:${fws}?${qcontent})*${fws}?${dquote})`;
+	const atom = `${atext}+`;
+	const word = `(?:${atom}|${quotedString})`;
+	const obsLocalPart = String.raw`(?:${word}(?:\.${word})*)`;
+	const localPart = `(?:${dotAtom}|${quotedString}|${obsLocalPart})`;
+	const obsDtext = `(?:${obsNoWsCtl}|${quotedPair})`;
+	const dtext = String.raw`(?:[\u0021-\u005A]|[\u005E-\u007E]|${obsDtext})`;
+	const domainLiteral = String.raw`(?:\[(?:${fws}?${dtext})*${fws}?])`;
+	const obsDomain = String.raw`(?:${atom}(?:\.${atom})${options.allowSingleLabelDomain ? '*' : '+'})`;
+	const domain = `(?:${dotAtom}|${domainLiteral}|${obsDomain})`;
+	const addrSpec = `${localPart}@${domain}`;
+
+	return options.exact ? new RegExp(`^${addrSpec}$`) : new RegExp(addrSpec, 'g');
 }

index.test-d.ts

@@ -4,3 +4,4 @@ import emailRegex from './index.js';
 expectType<RegExp>(emailRegex());
 expectType<RegExp>(emailRegex({}));
 expectType<RegExp>(emailRegex({exact: true}));
+expectType<RegExp>(emailRegex({exact: true, allowAmpersandEntity: true, allowSingleLabelDomain: true}));

package.json

@@ -39,7 +39,8 @@
 	],
 	"devDependencies": {
 		"ava": "^3.15.0",
-		"tsd": "^0.14.0",
+		"tsd": "^0.21.0",
+		"typescript": "^4.9.5",
 		"xo": "^0.39.1"
 	}
 }

readme.md

@@ -48,6 +48,20 @@ Only match an exact string.
 
 Useful with `RegExp#test` to check if a string is an email address.
 
+##### allowSingleLabelDomain
+
+Type: `boolean`\
+Default: `true`
+
+Allow emails with a domain that doesn't have a dot, such as `user@localhost` or `user@internal`.
+
+##### allowAmpersandEntity
+
+Type: `boolean`\
+Default: `false`
+
+Allow the ampersand HTML entity `&` to correspond to an ampersand `&` in the email address.
+
 ## Important
 
 If you run the regex against untrusted user input in a server context, you should [give it a timeout](https://github.com/sindresorhus/super-regex). It's also a good idea to limit the input to a reasonable length.

test.js

@@ -12,22 +12,61 @@ const fixtures = [
 	'[email protected]',
 	'[email protected]',
 	'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghiklm@sindresorhus.com',
-	'!#$%&`*+/=?^`{|}[email protected]',
 	'[email protected]',
 	'a@abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghikl.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghikl.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghikl.abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefg.hij',
 	'[email protected]',
-	'"\\a"@sindresorhus.com',
+	String.raw`"\a"@sindresorhus.com`,
 	'""@sindresorhus.com',
 	'"test"@sindresorhus.com',
-	'"\\""@sindresorhus.com',
+	String.raw`"\""@sindresorhus.com`,
 	'abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcdefghiklmn@sindresorhus.com',
 	'[email protected]',
 	'a@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.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.a.b.c.d.e.f.g.h.i.j.k.l.m.n.o.p.q.r.s.t.u.v',
 	'[email protected]',
 	'[email protected]',
-	'foo@[IPv6:2001:db8::2]'
+	'foo@[IPv6:2001:db8::2]',
+	// https://github.com/sindresorhus/email-regex/issues/2#issuecomment-404654677
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'email@[123.123.123.123]',
+	'"email"@example.com',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]',
+	// 'very.unusual.”@”.unusual.com',
+	'email@example',
+	'[email protected]',
+	'[email protected]',
+	'[email protected]'
 ];
 
+const fixturesCustomMatch = new Map([
+	// https://github.com/sindresorhus/email-regex/issues/9#issue-569014279
+	['f="nr@context",c=e("gos")', 'nr@context'],
+	// https://github.com/sindresorhus/email-regex/issues/2#issuecomment-404654677
+	[String.raw`very.”(),:;<>[]”.VERY.”very@\ "very”[email protected]`, '[email protected]'],
+	['#@%^%#$@#$@#.com', '#@%^%#$'],
+	['Joe Smith [email protected]', '[email protected]'],
+	['email@[email protected]', 'email@example'],
+	['[email protected]', '[email protected]'],
+	['[email protected]', '[email protected]'],
+	['[email protected] (Joe Smith)', '[email protected]'],
+	['just”not”[email protected]', '[email protected]'],
+	[String.raw`this\ is"really"not\[email protected]`, '[email protected]']
+]);
+
+for (const [input, expected] of fixturesCustomMatch) {
+	// If they match, we can't use them as notFixtures
+	console.assert(input !== expected, `Custom match fixture "${input}" does not match expected "${expected}"`);
+}
+
 const fixturesNot = [
 	'@',
 	'@io',
@@ -39,25 +78,67 @@ const fixturesNot = [
 	'sindre@[email protected]',
 	'mailto:[email protected]',
 	'foo.example.com',
-	'[email protected]'
+	'[email protected]',
+	'!#$%&amp;`*+/=?^`{|}[email protected]',
+	// https://github.com/sindresorhus/email-regex/issues/9#issue-569014279
+	'f="nr@context",c=e("gos")',
+	// https://github.com/sindresorhus/email-regex/issues/2#issuecomment-404654677
+	'plainaddress',
+	'@example.com',
+	'email.example.com',
+	'[email protected]',
+	'[email protected]',
+	'あいうえお@example.com',
+	'[email protected]',
+	'”(),:;<>[]@example.com',
+	'"(),:;<>[]@example.com',
+	String.raw`much.”more\ unusual”@example.com`
 ];
 
+function getFirstMatch(regex, text) {
+	const matches = regex.exec(text);
+
+	if (matches) {
+		return matches[0];
+	}
+}
+
 test('extract', t => {
 	for (const fixture of fixtures) {
-		t.is((emailRegex().exec(`foo ${fixture} bar`) || [])[0], fixture);
+		t.is(getFirstMatch(emailRegex(), `foo ${fixture} bar`), fixture);
 	}
 
-	t.is(emailRegex().exec('mailto:[email protected]')[0], '[email protected]');
+	for (const [input, expected] of fixturesCustomMatch) {
+		t.is(getFirstMatch(emailRegex(), input), expected, input); // eslint-disable-line ava/assertion-arguments
+	}
+
+	t.is(getFirstMatch(emailRegex(), 'mailto:[email protected]'), '[email protected]');
 });
 
 test('exact', t => {
 	for (const fixture of fixtures) {
-		t.true(emailRegex({exact: true}).test(fixture));
+		t.true(emailRegex({exact: true}).test(fixture), fixture); // eslint-disable-line ava/assertion-arguments
 	}
 });
 
+test('allowSingleLabelDomain', t => {
+	t.true(emailRegex({exact: true, allowSingleLabelDomain: true}).test('abc@sindresorhus'));
+	t.false(emailRegex({exact: true, allowSingleLabelDomain: false}).test('abc@sindresorhus'));
+	t.is(getFirstMatch(emailRegex({exact: false, allowSingleLabelDomain: true}), '#@%^%#$@#$@#.com'), '#@%^%#$');
+	t.is(getFirstMatch(emailRegex({exact: false, allowSingleLabelDomain: false}), '#@%^%#$@#$@#.com'), '#$@#.com');
+});
+
+test('allowAmpersandEntity', t => {
+	t.true(emailRegex({exact: true, allowAmpersandEntity: true}).test('!#$%&amp;`*+/=?^`{|}[email protected]'));
+	t.false(emailRegex({exact: true, allowAmpersandEntity: false}).test('!#$%&amp;`*+/=?^`{|}[email protected]'));
+});
+
 test('failures', t => {
 	for (const fixture of fixturesNot) {
-		t.false(emailRegex({exact: true}).test(fixture));
+		t.false(emailRegex({exact: true}).test(fixture), fixture); // eslint-disable-line ava/assertion-arguments
+	}
+
+	for (const input of fixturesCustomMatch.keys()) {
+		t.false(emailRegex({exact: true}).test(input), input); // eslint-disable-line ava/assertion-arguments
 	}
 });