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

README.md

@@ -250,6 +250,9 @@ ASCII nor UTF-8 (as Postgres will then accept but ignore non-ASCII bytes).
 For best results, always use PGRX with UTF-8, and set database encodings
 explicitly upon database creation.
 
+To easily convert `pgrx` temporal types (`pgrx::TimestampWithTimezone`, etc)
+to [`chrono`] compatible types, enable the `chrono` feature.
+
 ## Digging Deeper
 
  - [cargo-pgrx sub-command](cargo-pgrx/)

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"]
@@ -65,6 +66,7 @@ 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 +1,75 @@
+//! Tests for the `chrono` features of `cargo-pgrx`
+//!
+#![cfg(feature = "chrono")]
+
+#[cfg(any(test, feature = "pg_test"))]
+#[pgrx::pg_schema]
+mod tests {
+    #[allow(unused_imports)]
+    use crate as pgrx_tests;
+
+    use std::result::Result;
+
+    use chrono::{Datelike as _, Timelike as _, Utc};
+
+    use pgrx::pg_test;
+    use pgrx::DateTimeConversionError;
+
+    // Utility class for errors
+    type DtcResult<T> = Result<T, DateTimeConversionError>;
+
+    /// Ensure simple conversion ([`pgrx::Date`] -> [`chrono::NaiveDate`]) works
+    #[pg_test]
+    fn chrono_simple_date_conversion() -> DtcResult<()> {
+        let original = pgrx::Date::new(1970, 1, 1)?;
+        let d = chrono::NaiveDate::try_from(original)?;
+        assert_eq!(d.year(), original.year(), "year matches");
+        assert_eq!(d.month(), 1, "month matches");
+        assert_eq!(d.day(), 1, "day matches");
+        let backwards = pgrx::Date::try_from(d)?;
+        assert_eq!(backwards, original);
+        Ok(())
+    }
+
+    /// Ensure simple conversion ([`pgrx::Time`] -> [`chrono::NaiveTime`]) works
+    #[pg_test]
+    fn chrono_simple_time_conversion() -> DtcResult<()> {
+        let original = pgrx::Time::new(12, 1, 59.0000001)?;
+        let d = chrono::NaiveTime::try_from(original)?;
+        assert_eq!(d.hour(), 12, "hours match");
+        assert_eq!(d.minute(), 1, "minutes match");
+        assert_eq!(d.second(), 59, "seconds match");
+        assert_eq!(d.nanosecond(), 0, "nanoseconds are zero (pg only supports microseconds)");
+        let backwards = pgrx::Time::try_from(d)?;
+        assert_eq!(backwards, original);
+        Ok(())
+    }
+
+    /// Ensure simple conversion ([`pgrx::Timestamp`] -> [`chrono::NaiveDateTime`]) works
+    #[pg_test]
+    fn chrono_simple_timestamp_conversion() -> DtcResult<()> {
+        let original = pgrx::Timestamp::new(1970, 1, 1, 1, 1, 1.0)?;
+        let d = chrono::NaiveDateTime::try_from(original)?;
+        assert_eq!(d.hour(), 1, "hours match");
+        assert_eq!(d.minute(), 1, "minutes match");
+        assert_eq!(d.second(), 1, "seconds match");
+        assert_eq!(d.nanosecond(), 0, "nanoseconds are zero (pg only supports microseconds)");
+        let backwards = pgrx::Timestamp::try_from(d)?;
+        assert_eq!(backwards, original, "NaiveDateTime -> Timestamp return conversion failed");
+        Ok(())
+    }
+
+    /// Ensure simple conversion ([`pgrx::TimestampWithTimeZone`] -> [`chrono::DateTime<Utc>`]) works
+    #[pg_test]
+    fn chrono_simple_datetime_with_time_zone_conversion() -> DtcResult<()> {
+        let original = pgrx::TimestampWithTimeZone::with_timezone(1970, 1, 1, 1, 1, 1.0, "utc")?;
+        let d = chrono::DateTime::<Utc>::try_from(original)?;
+        assert_eq!(d.hour(), 1, "hours match");
+        assert_eq!(d.minute(), 1, "minutes match");
+        assert_eq!(d.second(), 1, "seconds match");
+        assert_eq!(d.nanosecond(), 0, "nanoseconds are zero (pg only supports microseconds)");
+        let backwards = pgrx::TimestampWithTimeZone::try_from(d)?;
+        assert_eq!(backwards, original);
+        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)