feat: add WASM support via web-time (#1037)

Support WASM environments by using web-time.
This was tested on a Cloudflare worker environment.

Cargo.lock

@@ -1233,6 +1233,7 @@ dependencies = [
  "url",
  "uuid",
  "walkdir",
+ "web-time",
  "webpki-roots",
 ]
 
@@ -2442,6 +2443,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "web-time"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a6580f308b1fad9207618087a65c04e7a10bc77e02c8e84e9b00dd4b12fa0bb"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
 [[package]]
 name = "webpki-roots"
 version = "0.26.7"

Cargo.toml

@@ -75,6 +75,9 @@ ed25519-dalek = { version = "2", optional = true }
 # email formats
 email_address = { version = "0.2.1", default-features = false }
 
+# webtime for wasm support
+web-time = { version = "1.1.0", optional = true }
+
 [dev-dependencies]
 pretty_assertions = "1"
 criterion = "0.5"
@@ -122,6 +125,9 @@ tokio1-boring-tls = ["tokio1", "boring-tls", "dep:tokio1_boring"]
 
 dkim = ["dep:base64", "dep:sha2", "dep:rsa", "dep:ed25519-dalek"]
 
+# wasm support
+web = ["dep:web-time"]
+
 [lints.rust]
 unexpected_cfgs = { level = "warn", check-cfg = ['cfg(lettre_ignore_tls_mismatch)'] }
 

src/lib.rs

@@ -107,6 +107,7 @@
 //! * **tracing**: Logging using the `tracing` crate
 //! * **mime03**: Allow creating a [`ContentType`] from an existing [mime 0.3] `Mime` struct
 //! * **dkim**: Add support for signing email with DKIM
+//! * **web**: WebAssembly support using the `web-time` crate for time operations
 //!
 //! [`SMTP`]: crate::transport::smtp
 //! [`sendmail`]: crate::transport::sendmail

src/message/dkim.rs

@@ -346,6 +346,13 @@ fn dkim_canonicalize_headers<'a>(
 /// Sign with Dkim a message by adding Dkim-Signature header created with configuration expressed by
 /// `dkim_config`
 pub fn dkim_sign(message: &mut Message, dkim_config: &DkimConfig) {
+    #[cfg(feature = "web")]
+    dkim_sign_fixed_time(
+        message,
+        dkim_config,
+        crate::message::to_std_systemtime(web_time::SystemTime::now()),
+    );
+    #[cfg(not(feature = "web"))]
     dkim_sign_fixed_time(message, dkim_config, SystemTime::now());
 }
 

src/message/header/date.rs

@@ -21,7 +21,12 @@ impl Date {
     ///
     /// Shortcut for `Date::new(SystemTime::now())`
     pub fn now() -> Self {
-        Self::new(SystemTime::now())
+        #[cfg(not(feature = "web"))]
+        return Self::new(SystemTime::now());
+        #[cfg(feature = "web")]
+        return Self::new(crate::message::to_std_systemtime(
+            web_time::SystemTime::now(),
+        ));
     }
 }
 

src/message/mod.rs

@@ -277,7 +277,10 @@ impl MessageBuilder {
     /// Shortcut for `self.date(SystemTime::now())`, it is automatically inserted
     /// if no date has been provided.
     pub fn date_now(self) -> Self {
-        self.date(SystemTime::now())
+        #[cfg(not(feature = "web"))]
+        return self.date(SystemTime::now());
+        #[cfg(feature = "web")]
+        return self.date(to_std_systemtime(web_time::SystemTime::now()));
     }
 
     /// Set or add mailbox to `ReplyTo` header
@@ -623,8 +626,17 @@ fn make_message_id() -> String {
     iter::repeat_with(fastrand::alphanumeric).take(36).collect()
 }
 
+#[cfg(feature = "web")]
+pub(crate) fn to_std_systemtime(time: web_time::SystemTime) -> std::time::SystemTime {
+    let duration = time
+        .duration_since(web_time::SystemTime::UNIX_EPOCH)
+        .unwrap();
+    std::time::SystemTime::UNIX_EPOCH + duration
+}
+
 #[cfg(test)]
 mod test {
+
     use std::time::{Duration, SystemTime};
 
     use pretty_assertions::assert_eq;