Stop using the regex crate for parsing addresses (#776)

Cargo.toml

@@ -20,7 +20,7 @@ maintenance = { status = "actively-developed" }
 
 [dependencies]
 idna = "0.2"
-once_cell = "1"
+once_cell = { version = "1", optional = true }
 tracing = { version = "0.1.16", default-features = false, features = ["std"], optional = true } # feature
 
 # builder
@@ -29,7 +29,6 @@ mime = { version = "0.3.4", optional = true }
 fastrand = { version = "1.4", optional = true }
 quoted_printable = { version = "0.4", optional = true }
 base64 = { version = "0.13", optional = true }
-regex = { version = "1", default-features = false, features = ["std", "unicode-case"] }
 email-encoding = { git = "https://github.com/lettre/email-encoding.git", rev = "ac7ab8630b8d012ade63869c89b2855e27b3ce7a", optional = true }
 
 # file transport
@@ -67,6 +66,7 @@ tokio1_rustls = { package = "tokio-rustls", version = "0.23", optional = true }
 sha2 = { version = "0.10", optional = true }
 rsa = { version = "0.6.0", optional = true }
 ed25519-dalek = { version = "1.0.1", optional = true }
+regex = { version = "1", default-features = false, features = ["std"], optional = true }
 
 # email formats
 email_address = { version = "0.2.1", default-features = false }
@@ -95,7 +95,7 @@ mime03 = ["mime"]
 file-transport = ["uuid"]
 file-transport-envelope = ["serde", "serde_json", "file-transport"]
 sendmail-transport = []
-smtp-transport = ["base64", "nom", "socket2"]
+smtp-transport = ["base64", "nom", "socket2", "once_cell"]
 
 pool = ["futures-util"]
 
@@ -109,7 +109,7 @@ tokio1 = ["tokio1_crate", "async-trait", "futures-io", "futures-util"]
 tokio1-native-tls = ["tokio1", "native-tls", "tokio1_native_tls_crate"]
 tokio1-rustls-tls = ["tokio1", "rustls-tls", "tokio1_rustls"]
 
-dkim = ["base64", "sha2", "rsa", "ed25519-dalek"]
+dkim = ["base64", "sha2", "rsa", "ed25519-dalek", "regex", "once_cell"]
 
 [package.metadata.docs.rs]
 all-features = true

src/address/types.rs

@@ -10,8 +10,6 @@ use std::{
 
 use email_address::EmailAddress;
 use idna::domain_to_ascii;
-use once_cell::sync::Lazy;
-use regex::Regex;
 
 /// Represents an email address with a user and a domain name.
 ///
@@ -56,9 +54,6 @@ pub struct Address {
     at_start: usize,
 }
 
-// literal form, ipv4 or ipv6 address (SMTP 4.1.3)
-static LITERAL_RE: Lazy<Regex> = Lazy::new(|| Regex::new(r"(?i)\[([A-f0-9:\.]+)\]\z").unwrap());
-
 impl Address {
     /// Creates a new email address from a user and domain.
     ///
@@ -132,16 +127,19 @@ impl Address {
     }
 
     fn check_domain_ascii(domain: &str) -> Result<(), AddressError> {
+        // Domain
         if EmailAddress::is_valid_domain(domain) {
             return Ok(());
         }
 
-        if let Some(caps) = LITERAL_RE.captures(domain) {
-            if let Some(cap) = caps.get(1) {
-                if cap.as_str().parse::<IpAddr>().is_ok() {
-                    return Ok(());
-                }
-            }
+        // IP
+        let ip = domain
+            .strip_prefix('[')
+            .and_then(|ip| ip.strip_suffix(']'))
+            .unwrap_or(domain);
+
+        if ip.parse::<IpAddr>().is_ok() {
+            return Ok(());
         }
 
         Err(AddressError::InvalidDomain)
@@ -259,7 +257,7 @@ mod tests {
     use super::*;
 
     #[test]
-    fn parse_address() {
+    fn ascii_address() {
         let addr_str = "something@example.com";
         let addr = Address::from_str(addr_str).unwrap();
         let addr2 = Address::new("something", "example.com").unwrap();
@@ -268,7 +266,34 @@ mod tests {
         assert_eq!(addr.domain(), "example.com");
         assert_eq!(addr2.user(), "something");
         assert_eq!(addr2.domain(), "example.com");
+    }
 
+    #[test]
+    fn ascii_address_ipv4() {
+        let addr_str = "something@1.1.1.1";
+        let addr = Address::from_str(addr_str).unwrap();
+        let addr2 = Address::new("something", "1.1.1.1").unwrap();
+        assert_eq!(addr, addr2);
+        assert_eq!(addr.user(), "something");
+        assert_eq!(addr.domain(), "1.1.1.1");
+        assert_eq!(addr2.user(), "something");
+        assert_eq!(addr2.domain(), "1.1.1.1");
+    }
+
+    #[test]
+    fn ascii_address_ipv6() {
+        let addr_str = "something@[2606:4700:4700::1111]";
+        let addr = Address::from_str(addr_str).unwrap();
+        let addr2 = Address::new("something", "[2606:4700:4700::1111]").unwrap();
+        assert_eq!(addr, addr2);
+        assert_eq!(addr.user(), "something");
+        assert_eq!(addr.domain(), "[2606:4700:4700::1111]");
+        assert_eq!(addr2.user(), "something");
+        assert_eq!(addr2.domain(), "[2606:4700:4700::1111]");
+    }
+
+    #[test]
+    fn check_parts() {
         assert!(Address::check_user("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa").is_err());
         assert!(
             Address::check_domain("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.com").is_err()