Add from_partial for YearMonth/MonthDay FFI (#351)

Author: Manishearth

src/builtins/core/month_day.rs

@@ -221,6 +221,16 @@ impl PlainMonthDay {
         )
     }
 
+    /// Create a `PlainYearMonth` from a `PartialDate`
+    pub fn from_partial(
+        partial: PartialDate,
+        overflow: Option<ArithmeticOverflow>,
+    ) -> TemporalResult<Self> {
+        partial
+            .calendar
+            .month_day_from_partial(&partial, overflow.unwrap_or_default())
+    }
+
     /// Create a `PlainMonthDay` with the provided fields from a [`PartialDate`].
     pub fn with(
         &self,

src/builtins/core/year_month.rs

@@ -520,9 +520,11 @@ impl PlainYearMonth {
     /// Create a `PlainYearMonth` from a `PartialYearMonth`
     pub fn from_partial(
         partial: PartialYearMonth,
-        overflow: ArithmeticOverflow,
+        overflow: Option<ArithmeticOverflow>,
     ) -> TemporalResult<Self> {
-        partial.calendar.year_month_from_partial(&partial, overflow)
+        partial
+            .calendar
+            .year_month_from_partial(&partial, overflow.unwrap_or_default())
     }
 
     // Converts a UTF-8 encoded string into a `PlainYearMonth`.
@@ -562,7 +564,7 @@ impl PlainYearMonth {
         // [[Day]] field of the [[ISODate]] internal slot of the result.
         // 14. Set isoDate to ? CalendarYearMonthFromFields(calendar, result, constrain).
         // 15. Return ! CreateTemporalYearMonth(isoDate, calendar).
-        PlainYearMonth::from_partial(partial, ArithmeticOverflow::Constrain)
+        PlainYearMonth::from_partial(partial, Some(ArithmeticOverflow::Constrain))
     }
 
     /// Returns the iso year value for this `YearMonth`.

temporal_capi/bindings/c/PlainMonthDay.h

@@ -343,3 +343,34 @@ impl TryFrom<ffi::PartialDate<'_>> for temporal_rs::partial::PartialDate {
         })
     }
 }
+
+impl TryFrom<ffi::PartialDate<'_>> for temporal_rs::partial::PartialYearMonth {
+    type Error = TemporalError;
+    fn try_from(other: ffi::PartialDate<'_>) -> Result<Self, TemporalError> {
+        use temporal_rs::TinyAsciiStr;
+
+        let month_code = if other.month_code.is_empty() {
+            None
+        } else {
+            Some(MonthCode::try_from_utf8(other.month_code.into()).map_err(TemporalError::from)?)
+        };
+
+        let era = if other.era.is_empty() {
+            None
+        } else {
+            Some(TinyAsciiStr::try_from_utf8(other.era.into()).map_err(|_| {
+                TemporalError::from(
+                    temporal_rs::TemporalError::range().with_message("Invalid era code."),
+                )
+            })?)
+        };
+        Ok(Self {
+            year: other.year.into(),
+            month: other.month.into(),
+            month_code,
+            era_year: other.era_year.into(),
+            era,
+            calendar: temporal_rs::Calendar::new(other.calendar.into()),
+        })
+    }
+}

temporal_capi/bindings/c/PlainYearMonth.h

@@ -38,6 +38,15 @@ pub mod ffi {
             .map_err(Into::into)
         }
 
+        pub fn from_partial(
+            partial: PartialDate,
+            overflow: Option<ArithmeticOverflow>,
+        ) -> Result<Box<PlainMonthDay>, TemporalError> {
+            temporal_rs::PlainMonthDay::from_partial(partial.try_into()?, overflow.map(Into::into))
+                .map(|x| Box::new(PlainMonthDay(x)))
+                .map_err(Into::into)
+        }
+
         pub fn with(
             &self,
             partial: PartialDate,