RUST-977 Support RFC 3339 to bson::DateTime conversion without chrono feature flag (#317)

Author: karmenliang

src/bson.rs

@@ -423,7 +423,7 @@ impl Bson {
             Bson::ObjectId(v) => json!({"$oid": v.to_hex()}),
             Bson::DateTime(v) if v.timestamp_millis() >= 0 && v.to_chrono().year() <= 99999 => {
                 json!({
-                    "$date": v.to_rfc3339(),
+                    "$date": v.to_rfc3339_string(),
                 })
             }
             Bson::DateTime(v) => json!({
@@ -573,7 +573,7 @@ impl Bson {
             }
             Bson::DateTime(v) if v.timestamp_millis() >= 0 && v.to_chrono().year() <= 9999 => {
                 doc! {
-                    "$date": v.to_rfc3339(),
+                    "$date": v.to_rfc3339_string(),
                 }
             }
             Bson::DateTime(v) => doc! {

src/datetime.rs

@@ -1,5 +1,7 @@
 use std::{
+    error,
     fmt::{self, Display},
+    result,
     time::{Duration, SystemTime},
 };
 
@@ -167,10 +169,21 @@ impl crate::DateTime {
         self.0
     }
 
-    pub(crate) fn to_rfc3339(self) -> String {
+    /// Convert this [`DateTime`] to an RFC 3339 formatted string.
+    pub fn to_rfc3339_string(self) -> String {
         self.to_chrono()
             .to_rfc3339_opts(chrono::SecondsFormat::AutoSi, true)
     }
+
+    /// Convert the given RFC 3339 formatted string to a [`DateTime`], truncating it to millisecond
+    /// precision.
+    pub fn parse_rfc3339_str(s: impl AsRef<str>) -> Result<Self> {
+        let date = chrono::DateTime::<chrono::FixedOffset>::parse_from_rfc3339(s.as_ref())
+            .map_err(|e| Error::InvalidTimestamp {
+                message: e.to_string(),
+            })?;
+        Ok(Self::from_chrono(date))
+    }
 }
 
 impl fmt::Debug for crate::DateTime {
@@ -220,3 +233,27 @@ impl<T: chrono::TimeZone> From<chrono::DateTime<T>> for crate::DateTime {
         Self::from_chrono(x)
     }
 }
+
+/// Errors that can occur during [`DateTime`] construction and generation.
+#[derive(Clone, Debug)]
+#[non_exhaustive]
+pub enum Error {
+    /// Error returned when an invalid datetime format is provided to a conversion method.
+    #[non_exhaustive]
+    InvalidTimestamp { message: String },
+}
+
+/// Alias for `Result<T, DateTime::Error>`
+pub type Result<T> = result::Result<T, Error>;
+
+impl fmt::Display for Error {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Error::InvalidTimestamp { message } => {
+                write!(fmt, "{}", message)
+            }
+        }
+    }
+}
+
+impl error::Error for Error {}

src/lib.rs

@@ -288,7 +288,7 @@ pub use self::{
 #[macro_use]
 mod macros;
 mod bson;
-mod datetime;
+pub mod datetime;
 pub mod de;
 pub mod decimal128;
 pub mod document;

src/serde_helpers.rs

@@ -252,7 +252,7 @@ pub mod rfc3339_string_as_bson_datetime {
         D: Deserializer<'de>,
     {
         let date = DateTime::deserialize(deserializer)?;
-        Ok(date.to_rfc3339())
+        Ok(date.to_rfc3339_string())
     }
 
     /// Serializes an ISO string as a DateTime.
@@ -297,7 +297,7 @@ pub mod bson_datetime_as_rfc3339_string {
 
     /// Serializes a [`crate::DateTime`] as an RFC 3339 (ISO 8601) formatted string.
     pub fn serialize<S: Serializer>(val: &DateTime, serializer: S) -> Result<S::Ok, S::Error> {
-        serializer.serialize_str(&val.to_rfc3339())
+        serializer.serialize_str(&val.to_rfc3339_string())
     }
 }
 

src/tests/datetime.rs

@@ -0,0 +1,25 @@
+use crate::tests::LOCK;
+use std::str::FromStr;
+
+#[test]
+fn rfc3339_to_datetime() {
+    let _guard = LOCK.run_concurrently();
+
+    let rfc = "2020-06-09T10:58:07.095Z";
+    let date = chrono::DateTime::<chrono::Utc>::from_str(rfc).unwrap();
+    let parsed = crate::DateTime::parse_rfc3339_str(rfc).unwrap();
+    assert_eq!(parsed, crate::DateTime::from_chrono(date));
+    assert_eq!(crate::DateTime::to_rfc3339_string(parsed), rfc);
+}
+
+#[test]
+fn invalid_rfc3339_to_datetime() {
+    let _guard = LOCK.run_concurrently();
+
+    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::parse_rfc3339_str(a).is_err());
+    assert!(crate::DateTime::parse_rfc3339_str(b).is_err());
+    assert!(crate::DateTime::parse_rfc3339_str(c).is_err());
+}

src/tests/mod.rs

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