Add native support for WASM targets

Cargo.toml

@@ -20,6 +20,14 @@ cfg-if = "1.0.0"
 thiserror = { version = "1.0.30", optional = true }
 nom = { version = "7.1.0", optional = true }
 
+[target.'cfg(not(target_family = "wasm"))'.dependencies]
+time = { version = "0.3.7", features = ["macros"] }
+
+[target.'cfg(target_family = "wasm")'.dependencies]
+js-sys = { version = "0.3.64", optional = true }
+time = { version = "0.3.7", features = ["macros", "wasm-bindgen"] }
+wasm-bindgen = "0.2.87"
+
 [target.'cfg(windows)'.dependencies]
 windows-sys = { version = "0.32.0", features = ["Win32_System_Time", "Win32_Foundation"], optional = true }
 
@@ -31,7 +39,7 @@ serde = { version = "1.0.136", features = ["derive"] }
 
 [features]
 default = ["db"]
-system = ["windows-sys", "thiserror", "db"]
+system = ["windows-sys", "js-sys", "thiserror", "db"]
 posix-tz = ["nom", "thiserror", "db"]
 db = []
 

src/binary_search.rs

@@ -41,19 +41,23 @@ pub fn binary_search<F: Fn(usize) -> Ordering>(start: usize, end: usize, cmp: F)
     }
 }
 
-#[test]
-fn test_binary_search() {
-    assert_eq!(binary_search(0, 8, |x| x.cmp(&6)), Some(6));
-    assert_eq!(binary_search(0, 5000, |x| x.cmp(&1337)), Some(1337));
-    assert_eq!(binary_search(0, 5000, |x| x.cmp(&9000)), None);
-    assert_eq!(binary_search(30, 50, |x| x.cmp(&42)), Some(42));
-    assert_eq!(binary_search(300, 500, |x| x.cmp(&42)), None);
-    assert_eq!(
-        binary_search(0, 500, |x| if x < 42 {
-            Ordering::Less
-        } else {
-            Ordering::Greater
-        }),
-        None
-    );
-}
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_binary_search() {
+        assert_eq!(super::binary_search(0, 8, |x| x.cmp(&6)), Some(6));
+        assert_eq!(super::binary_search(0, 5000, |x| x.cmp(&1337)), Some(1337));
+        assert_eq!(super::binary_search(0, 5000, |x| x.cmp(&9000)), None);
+        assert_eq!(super::binary_search(30, 50, |x| x.cmp(&42)), Some(42));
+        assert_eq!(super::binary_search(300, 500, |x| x.cmp(&42)), None);
+        assert_eq!(
+            super::binary_search(0, 500, |x| if x < 42 {
+                super::Ordering::Less
+            } else {
+                super::Ordering::Greater
+            }),
+            None
+        );
+    }
+
+}

src/lib.rs

@@ -60,7 +60,7 @@ pub trait PrimitiveDateTimeExt: sealing::PrimitiveDateTimeExt {
     ///
     /// * `tz`: the target timezone.
     ///
-    /// returns: OffsetResult<OffsetDateTime>
+    /// returns: `OffsetResult<OffsetDateTime>`
     fn assume_timezone<T: TimeZone>(&self, tz: &T) -> OffsetResult<OffsetDateTime>;
 
     /// Creates a new OffsetDateTime with the proper offset in the given timezone.

src/system.rs

@@ -26,10 +26,19 @@
 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+//! Support for getting time zone information from the target system.
+//! 
+//! Currently only supported for Windows, Unix, and WASM targets.
+
 use crate::timezones::get_by_name;
 use crate::Tz;
 use thiserror::Error;
 
+#[cfg(target_family = "wasm")]
+use js_sys::{ Intl, Reflect, Array, Object };
+#[cfg(target_family = "wasm")]
+use wasm_bindgen::JsValue;
+
 #[derive(Debug, Error)]
 pub enum Error {
     /// An IO error has occurred.
@@ -52,8 +61,18 @@ pub enum Error {
     /// The timezone doesn't exist in the crate's database.
     #[error("unknown timezone name")]
     Unknown,
+
+    /// The target platform is not supported. Windows, Unix, and WASM targets are the only supported for the system feature at this moment.
+    #[error("unsupported platform")]
+    Unsupported,
 }
 
+/// Gets the current timezone from the system.
+/// 
+/// Currently only supported for Windows, Unix, and WASM targets.
+/// 
+/// # Errors
+/// Returns an [Error](enum@Error) if the timezone cannot be determined.
 pub fn get_timezone() -> Result<&'static Tz, Error> {
     cfg_if::cfg_if! {
         if #[cfg(unix)] {
@@ -67,7 +86,7 @@ pub fn get_timezone() -> Result<&'static Tz, Error> {
             } else {
                 Err(Error::Undetermined)
             }
-        } else {
+        } else if #[cfg(windows)] {
             unsafe {
                 use windows_sys::Win32::System::Time::GetDynamicTimeZoneInformation;
                 use windows_sys::Win32::System::Time::DYNAMIC_TIME_ZONE_INFORMATION;
@@ -89,6 +108,19 @@ pub fn get_timezone() -> Result<&'static Tz, Error> {
                     Ok(tz)
                 }
             }
+        } else if #[cfg(target_family = "wasm")] {
+            let options = Intl::DateTimeFormat::new(&Array::new(), &Object::new())
+                .resolved_options();
+
+            let tz = Reflect::get(&options, &JsValue::from("timeZone"))
+                .map_err(|_| Error::Undetermined)?
+                .as_string()
+                .ok_or(Error::Unicode)?;
+
+            let tz = get_by_name(&tz).ok_or(Error::Unknown)?;
+            Ok(tz)
+        } else {
+            Err(Error::Unsupported)
         }
     }
 }