RUST-977 Support RFC 3339 to bson::DateTime conversion without chrono feature flag

src/datetime.rs

@@ -171,6 +171,16 @@ impl crate::DateTime {
         self.to_chrono()
             .to_rfc3339_opts(chrono::SecondsFormat::AutoSi, true)
     }
+
+    /// Convert the given RFC 3339 format string to a [`DateTime`].
+    pub fn from_rfc3339(s: impl AsRef<str>) -> Result<Self, crate::de::Error> {
+        match chrono::DateTime::<chrono::FixedOffset>::parse_from_rfc3339(s.as_ref()) {
+            Ok(d) => Ok(Self::from_chrono(d)),
+            Err(e) => Err(crate::de::Error::InvalidTimestamp {
+                message: e.to_string(),
+            }),
+        }
+    }
 }
 
 impl fmt::Debug for crate::DateTime {

src/de/error.rs

@@ -15,6 +15,12 @@ pub enum Error {
     /// while decoding a UTF-8 String from the input data.
     InvalidUtf8String(string::FromUtf8Error),
 
+    /// An error encountered during the conversion of one datetime format to another.
+    InvalidTimestamp {
+        /// A message describing the error.
+        message: String,
+    },
+
     /// While decoding a `Document` from bytes, an unexpected or unsupported element type was
     /// encountered.
     #[non_exhaustive]
@@ -55,6 +61,7 @@ impl fmt::Display for Error {
         match *self {
             Error::Io(ref inner) => inner.fmt(fmt),
             Error::InvalidUtf8String(ref inner) => inner.fmt(fmt),
+            Error::InvalidTimestamp { ref message } => message.fmt(fmt),
             Error::UnrecognizedDocumentElementType {
                 ref key,
                 element_type,

src/tests/datetime.rs

@@ -0,0 +1,21 @@
+use std::str::FromStr;
+
+#[test]
+fn rfc3339_to_datetime() {
+    let rfc = "2020-06-09T10:58:07.095Z";
+    let date = chrono::DateTime::<chrono::Utc>::from_str(rfc).unwrap();
+    assert_eq!(
+        crate::DateTime::from_rfc3339(rfc).unwrap(),
+        crate::DateTime::from_chrono(date)
+    );
+}
+
+#[test]
+fn invalid_rfc3339_to_datetime() {
+    let a = "2020-06-09T10:58:07-095Z";
+    let b = "2020-06-09T10:58:07.095";
+    let c = "2020-06-09T10:62:07.095Z";
+    assert!(crate::DateTime::from_rfc3339(a).is_err());
+    assert!(crate::DateTime::from_rfc3339(b).is_err());
+    assert!(crate::DateTime::from_rfc3339(c).is_err());
+}

src/tests/mod.rs

@@ -1,4 +1,5 @@
 mod binary_subtype;
+mod datetime;
 mod modules;
 mod serde;
 mod spec;