Patch for partial records (#94)

This PR is a patch for some things I found while doing some
implementation of `temporal_rs` in Boa.

The things the PR addresses / patches

- Adds a `DateTime::from_date_and_time`
- I noticed that the `with` methods weren't checking whether the
partials were empty, which would not be valid. This update throws an
early error if the partial provided is empty.
- Changed the internal way for constructing a `TemporalFields` from a
`PartialDate`. Primarily, after doing the implementation, I don't think
having a `From<PartialDate> for TemporalFields` is a good idea. We will
still need it internally, but I'm now leaning more towards using the
calendar to generate the fields from a partial. Something akin to
`calendar::create_fields_from_partial_date(partial_date)`.

src/components/date.rs

@@ -26,7 +26,7 @@ use super::{
 
 // TODO: PrepareTemporalFields expects a type error to be thrown when all partial fields are None/undefined.
 /// A partial Date that may or may not be complete.
-#[derive(Debug, Default, Clone, Copy)]
+#[derive(Debug, Default, Clone, Copy, PartialEq)]
 pub struct PartialDate {
     // A potentially set `year` field.
     pub year: Option<i32>,
@@ -42,6 +42,13 @@ pub struct PartialDate {
     pub era_year: Option<i32>,
 }
 
+impl PartialDate {
+    /// Returns a boolean for if the current `PartialDate` is empty.
+    pub(crate) fn is_empty(&self) -> bool {
+        *self == Self::default()
+    }
+}
+
 /// The native Rust implementation of `Temporal.PlainDate`.
 #[non_exhaustive]
 #[derive(Debug, Default, Clone, PartialEq, Eq)]
@@ -234,10 +241,13 @@ impl Date {
         partial: PartialDate,
         overflow: Option<ArithmeticOverflow>,
     ) -> TemporalResult<Self> {
+        if partial.is_empty() {
+            return Err(TemporalError::r#type().with_message("A PartialDate must have a field."));
+        }
         // 6. Let fieldsResult be ? PrepareCalendarFieldsAndFieldNames(calendarRec, temporalDate, « "day", "month", "monthCode", "year" »).
         let fields = TemporalFields::from(self);
         // 7. Let partialDate be ? PrepareTemporalFields(temporalDateLike, fieldsResult.[[FieldNames]], partial).
-        let partial_fields = TemporalFields::from(partial);
+        let partial_fields = TemporalFields::from_partial_date(&partial);
 
         // 8. Let fields be ? CalendarMergeFields(calendarRec, fieldsResult.[[Fields]], partialDate).
         let mut merge_result = fields.merge_fields(&partial_fields, self.calendar())?;
@@ -617,6 +627,21 @@ mod tests {
         assert_eq!(result.days(), 9719.0,);
     }
 
+    #[test]
+    fn date_with_empty_error() {
+        let base = Date::new(
+            1976,
+            11,
+            18,
+            Calendar::default(),
+            ArithmeticOverflow::Constrain,
+        )
+        .unwrap();
+
+        let err = base.with(PartialDate::default(), None);
+        assert!(err.is_err());
+    }
+
     #[test]
     fn basic_date_with() {
         let base = Date::new(

src/components/datetime.rs

@@ -24,8 +24,10 @@ use super::{
 /// A partial DateTime record
 #[derive(Debug, Default, Copy, Clone)]
 pub struct PartialDateTime {
-    date: PartialDate,
-    time: PartialTime,
+    /// The `PartialDate` portion of a `PartialDateTime`
+    pub date: PartialDate,
+    /// The `PartialTime` portion of a `PartialDateTime`
+    pub time: PartialTime,
 }
 
 /// The native Rust implementation of `Temporal.PlainDateTime`
@@ -250,16 +252,29 @@ impl DateTime {
         ))
     }
 
+    /// Create a `DateTime` from a `Date` and a `Time`.
+    pub fn from_date_and_time(date: Date, time: Time) -> TemporalResult<Self> {
+        Ok(Self::new_unchecked(
+            IsoDateTime::new(date.iso, time.iso)?,
+            date.calendar().clone(),
+        ))
+    }
+
     /// Creates a new `DateTime` with the fields of a `PartialDateTime`.
     #[inline]
     pub fn with(
         &self,
         partial_datetime: PartialDateTime,
         overflow: Option<ArithmeticOverflow>,
     ) -> TemporalResult<Self> {
+        if partial_datetime.date.is_empty() && partial_datetime.time.is_empty() {
+            return Err(
+                TemporalError::r#type().with_message("A PartialDateTime must have a valid field.")
+            );
+        }
         // Determine the Date from the provided fields.
         let fields = TemporalFields::from(self);
-        let partial_fields = TemporalFields::from(partial_datetime.date);
+        let partial_fields = TemporalFields::from_partial_date(&partial_datetime.date);
 
         let mut merge_result = fields.merge_fields(&partial_fields, self.calendar())?;
 
@@ -775,6 +790,15 @@ mod tests {
         );
     }
 
+    #[test]
+    fn datetime_with_empty_partial() {
+        let pdt =
+            DateTime::new(2020, 1, 31, 12, 34, 56, 987, 654, 321, Calendar::default()).unwrap();
+
+        let err = pdt.with(PartialDateTime::default(), None);
+        assert!(err.is_err());
+    }
+
     // options-undefined.js
     #[test]
     fn datetime_add_test() {

src/components/time.rs

@@ -17,7 +17,7 @@ use super::{duration::normalized::NormalizedTimeDuration, DateTime};
 use std::str::FromStr;
 
 /// A `PartialTime` represents partially filled `Time` fields.
-#[derive(Debug, Default, Clone, Copy)]
+#[derive(Debug, Default, Clone, Copy, PartialEq)]
 pub struct PartialTime {
     // A potentially set `hour` field.
     pub hour: Option<i32>,
@@ -33,6 +33,12 @@ pub struct PartialTime {
     pub nanosecond: Option<i32>,
 }
 
+impl PartialTime {
+    pub(crate) fn is_empty(&self) -> bool {
+        *self == Self::default()
+    }
+}
+
 /// The native Rust implementation of `Temporal.PlainTime`.
 #[non_exhaustive]
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
@@ -180,6 +186,10 @@ impl Time {
         partial: PartialTime,
         overflow: Option<ArithmeticOverflow>,
     ) -> TemporalResult<Self> {
+        if partial.is_empty() {
+            return Err(TemporalError::r#type().with_message("PartialTime cannot be empty."));
+        }
+
         let iso = self
             .iso
             .with(partial, overflow.unwrap_or(ArithmeticOverflow::Constrain))?;

src/fields.rs

@@ -471,6 +471,40 @@ impl TemporalFields {
 
         Ok(result)
     }
+
+    /// Creates a `TemporalField` from a `PartialDate`.
+    pub(crate) fn from_partial_date(partial: &PartialDate) -> Self {
+        let mut bit_map = FieldMap::empty();
+        if partial.year.is_some() {
+            bit_map.set(FieldMap::YEAR, true)
+        };
+        if partial.month.is_some() {
+            bit_map.set(FieldMap::MONTH, true)
+        };
+        if partial.month_code.is_some() {
+            bit_map.set(FieldMap::MONTH_CODE, true)
+        };
+        if partial.day.is_some() {
+            bit_map.set(FieldMap::DAY, true)
+        };
+        if partial.era.is_some() {
+            bit_map.set(FieldMap::ERA, true)
+        }
+        if partial.era_year.is_some() {
+            bit_map.set(FieldMap::ERA_YEAR, true)
+        }
+
+        Self {
+            bit_map,
+            year: partial.year,
+            month: partial.month,
+            month_code: partial.month_code,
+            day: partial.day,
+            era: partial.era,
+            era_year: partial.era_year,
+            ..Default::default()
+        }
+    }
 }
 
 impl From<&DateTime> for TemporalFields {
@@ -504,38 +538,10 @@ impl From<&Date> for TemporalFields {
     }
 }
 
+// TODO: Remove in favor of a more formal `TemporalFields::create_from_partial method`
 impl From<PartialDate> for TemporalFields {
     fn from(value: PartialDate) -> Self {
-        let mut bit_map = FieldMap::empty();
-        if value.year.is_some() {
-            bit_map.set(FieldMap::YEAR, true)
-        };
-        if value.month.is_some() {
-            bit_map.set(FieldMap::MONTH, true)
-        };
-        if value.month_code.is_some() {
-            bit_map.set(FieldMap::MONTH_CODE, true)
-        };
-        if value.day.is_some() {
-            bit_map.set(FieldMap::DAY, true)
-        };
-        if value.era.is_some() {
-            bit_map.set(FieldMap::ERA, true)
-        }
-        if value.era_year.is_some() {
-            bit_map.set(FieldMap::ERA_YEAR, true)
-        }
-
-        Self {
-            bit_map,
-            year: value.year,
-            month: value.month,
-            month_code: value.month_code,
-            day: value.day,
-            era: value.era,
-            era_year: value.era_year,
-            ..Default::default()
-        }
+        Self::from_partial_date(&value)
     }
 }