feat(pgrx): add chrono feature for easy conversions

This commit adds a `chrono` feature flag to `pgrx`, which enables
conversions between `pgrx` native date/time (with or without timezone)
and `chrono` types like `NaiveDateTime`.

Cargo.toml

@@ -71,6 +71,7 @@ thiserror = "1"
 unescape = "0.1.0" # for escaped-character-handling
 url = "2.4.1" # the non-existent std::web
 walkdir = "2" # directory recursion
+chrono = "0.4.35" # conversions to chrono data structures
 
 [profile.dev]
 # Only include line tables in debuginfo. This reduces the size of target/ (after

pgrx-tests/Cargo.toml

@@ -38,6 +38,7 @@ pg_test = [ ]
 proptest = [ "dep:proptest" ]
 cshim = [ "pgrx/cshim" ]
 no-schema-generation = [ "pgrx/no-schema-generation", "pgrx-macros/no-schema-generation" ]
+chrono = [ "dep:chrono", "pgrx/chrono" ]
 
 [package.metadata.docs.rs]
 features = ["pg14", "proptest"]
@@ -64,6 +65,7 @@ serde = "1.0"
 serde_json = "1.0"
 sysinfo = "0.29.10"
 rand = "0.8.5"
+chrono = { workspace = true, optional = true }
 
 [dependencies.pgrx] # Not unified in workspace due to default-features key
 path = "../pgrx"

pgrx-tests/src/tests/chrono_tests.rs

@@ -0,0 +1,32 @@
+#![cfg(feature = "chrono")]
+use pgrx::prelude::*;
+
+#[cfg(any(test, feature = "pg_test"))]
+#[pgrx::pg_schema]
+mod tests {
+    #[allow(unused_imports)]
+    use crate as pgrx_tests;
+
+    use std::result::Result;
+
+    use pgrx::datum::Date as PgrxDate;
+    use pgrx::pg_test;
+    use pgrx::DateTimeConversionError;
+
+    use chrono::Datelike as _;
+    use chrono::NaiveDate as ChronoNaiveDate;
+
+    // Utility class for errors
+    type DateTimeConversionResult<T> = Result<T, DateTimeConversionError>;
+
+    /// Ensure simple conversion ([`pgrx::Date`] -> [`chrono::NaiveDate`]) works
+    #[pg_test]
+    fn chrono_simple_date_conversion() -> DateTimeConversionResult<()> {
+        let original = PgrxDate::new(1970, 1, 1)?;
+        let d = ChronoNaiveDate::try_from(original)?;
+        assert_eq!(d.year(), original.year());
+        assert_eq!(d.month(), 1);
+        assert_eq!(d.day(), 1);
+        Ok(())
+    }
+}

pgrx-tests/src/tests/mod.rs

@@ -14,6 +14,8 @@ mod attributes_tests;
 mod bgworker_tests;
 mod bytea_tests;
 mod cfg_tests;
+#[cfg(feature = "chrono")]
+mod chrono_tests;
 mod composite_type_tests;
 mod datetime_tests;
 mod default_arg_value_tests;

pgrx/Cargo.toml

@@ -35,6 +35,7 @@ pg15 = [ "pgrx-pg-sys/pg15" ]
 pg16 = [ "pgrx-pg-sys/pg16" ]
 no-schema-generation = ["pgrx-macros/no-schema-generation", "pgrx-sql-entity-graph/no-schema-generation"]
 unsafe-postgres = []     # when trying to compile against something that looks like Postgres but claims to be diffent
+chrono = [ "dep:chrono" ]
 
 [package.metadata.docs.rs]
 features = ["pg14", "cshim"]
@@ -59,6 +60,7 @@ enum-map = "2.6.3"
 atomic-traits = "0.3.0" # PgAtomic and shmem init
 bitflags = "2.4.0" # BackgroundWorker
 bitvec = "1.0" # processing array nullbitmaps
+chrono = { workspace = true, optional = true } # Conversions to chrono date time types 
 heapless = "0.8" # shmem and PgLwLock
 libc.workspace = true # FFI type compat
 seahash = "4.1.0" # derive(PostgresHash)

pgrx/src/datum/datetime_support/chrono.rs

@@ -0,0 +1,19 @@
+//! This module contains implementations and functionality that enables [`pgrx`] types (ex. [`pgrx::datum::Date`])
+//! to be converted to [`chrono`] data types (ex. [`chrono::Date`])
+#![cfg(feature = "chrono")]
+
+use std::convert::TryFrom;
+
+use chrono;
+
+use crate::datum::datetime_support::DateTimeConversionError;
+use crate::datum::Date;
+
+impl TryFrom<Date> for chrono::naive::NaiveDate {
+    type Error = DateTimeConversionError;
+
+    fn try_from(d: Date) -> Result<chrono::NaiveDate, DateTimeConversionError> {
+        chrono::NaiveDate::from_ymd_opt(d.year(), d.month().into(), d.day().into())
+            .ok_or_else(|| DateTimeConversionError::InvalidFormat)
+    }
+}

pgrx/src/datum/datetime_support/mod.rs

@@ -22,6 +22,9 @@ use std::marker::PhantomData;
 mod ctor;
 mod ops;
 
+#[cfg(feature = "chrono")]
+mod chrono;
+
 pub use ctor::*;
 
 /// Tags to identify which "part" of a date or time-type value to extract or truncate to