Optionally implement Arbitrary for Naive{Date,Time,DateTime}

CHANGELOG.md

@@ -11,6 +11,12 @@ breakage if you use `no-default-features`.
 There were/are numerous minor versions before 1.0 due to the language changes.
 Versions with only mechanical changes will be omitted from the following list.
 
+## Unreleased
+
+* Implement `arbitrary::Arbitrary` for `NaiveDate`, `NaiveTime`, and
+  `NaiveDateTime`.  You need to enable the "arbitrary" feature to get these
+  impls.
+
 ## 0.4.22
 
 * Allow wasmbindgen to be optional on `wasm32-unknown-unknown` target [(#771)](https://github.com/chronotope/chrono/pull/771)

Cargo.toml

@@ -41,6 +41,7 @@ pure-rust-locales = { version = "0.5.2", optional = true }
 criterion = { version = "0.3", optional = true }
 rkyv = {version = "0.7", optional = true}
 iana-time-zone = { version = "0.1.44", optional = true, features = ["fallback"] }
+arbitrary = { version = "1.0.0", features = ["derive"], optional = true }
 
 [target.'cfg(all(target_arch = "wasm32", not(any(target_os = "emscripten", target_os = "wasi"))))'.dependencies]
 wasm-bindgen = { version = "0.2", optional = true }

src/naive/date.rs

@@ -176,6 +176,15 @@ pub const MIN_DATE: NaiveDate = NaiveDate::MIN;
 #[deprecated(since = "0.4.20", note = "Use NaiveDate::MAX instead")]
 pub const MAX_DATE: NaiveDate = NaiveDate::MAX;
 
+#[cfg(feature = "arbitrary")]
+impl arbitrary::Arbitrary<'_> for NaiveDate {
+    fn arbitrary(u: &mut arbitrary::Unstructured) -> arbitrary::Result<NaiveDate> {
+        let year = u.int_in_range(MIN_YEAR..=MAX_YEAR)?;
+        let ord = u.int_in_range(1..=366)?;
+        NaiveDate::from_yo_opt(year, ord).ok_or(arbitrary::Error::IncorrectFormat)
+    }
+}
+
 // as it is hard to verify year flags in `NaiveDate::MIN` and `NaiveDate::MAX`,
 // we use a separate run-time test.
 #[test]

src/naive/datetime/mod.rs

@@ -73,6 +73,7 @@ pub const MAX_DATETIME: NaiveDateTime = NaiveDateTime::MAX;
 /// ```
 #[derive(PartialEq, Eq, Hash, PartialOrd, Ord, Copy, Clone)]
 #[cfg_attr(feature = "rkyv", derive(Archive, Deserialize, Serialize))]
+#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 pub struct NaiveDateTime {
     date: NaiveDate,
     time: NaiveTime,

src/naive/time/mod.rs

@@ -194,6 +194,15 @@ pub struct NaiveTime {
     frac: u32,
 }
 
+#[cfg(feature = "arbitrary")]
+impl arbitrary::Arbitrary<'_> for NaiveTime {
+    fn arbitrary(u: &mut arbitrary::Unstructured) -> arbitrary::Result<NaiveTime> {
+        let secs = u.int_in_range(0..=86_400)?;
+        let frac = u.int_in_range(0..=2_000_000_000)?;
+        Ok(NaiveTime { secs, frac })
+    }
+}
+
 impl NaiveTime {
     /// Makes a new `NaiveTime` from hour, minute and second.
     ///