Provide a constructor of LocalDateTime from date and time parts

Author: ilya-g

core/common/src/LocalDate.kt

@@ -119,7 +119,7 @@ public fun LocalDate.atTime(hour: Int, minute: Int, second: Int = 0, nanosecond:
  * For finding an instant that corresponds to the start of a date in a particular time zone consider using
  * [LocalDate.atStartOfDayIn] function because a day does not always start at the fixed time 0:00:00.
  */
-public fun LocalDate.atTime(time: LocalTime): LocalDateTime = atTime(time.hour, time.minute, time.second, time.nanosecond)
+public fun LocalDate.atTime(time: LocalTime): LocalDateTime = LocalDateTime(this, time)
 
 
 /**

core/common/src/LocalDateTime.kt

@@ -83,6 +83,11 @@ public expect class LocalDateTime : Comparable<LocalDateTime> {
      */
     public constructor(year: Int, month: Month, dayOfMonth: Int, hour: Int, minute: Int, second: Int = 0, nanosecond: Int = 0)
 
+    /**
+     * Constructs a [LocalDateTime] instance by combining the given [date] and [time] parts.
+     */
+    public constructor(date: LocalDate, time: LocalTime)
+
     /** Returns the year component of the date. */
     public val year: Int
     /** Returns the number-of-month (1..12) component of the date. */

core/common/src/LocalTime.kt

@@ -110,4 +110,4 @@ public fun LocalTime.atDate(year: Int, month: Month, dayOfMonth: Int = 0): Local
 /**
  * Combines this time's components with the specified [LocalDate] components into a [LocalDateTime] value.
  */
-public fun LocalTime.atDate(date: LocalDate): LocalDateTime = atDate(date.year, date.monthNumber, date.dayOfMonth)
+public fun LocalTime.atDate(date: LocalDate): LocalDateTime = LocalDateTime(date, this)

core/common/test/LocalDateTimeTest.kt

@@ -86,6 +86,15 @@ class LocalDateTimeTest {
         println(localFixed.dayOfWeek)
     }
 
+    @Test
+    fun constructFromParts() {
+        val dt = Clock.System.now().toLocalDateTime(TimeZone.UTC)
+        val dt2 = LocalDateTime(dt.date, dt.time)
+        assertEquals(dt2, dt)
+        assertEquals(dt2.date, dt.date)
+        assertEquals(dt2.time, dt.time)
+    }
+
     /* Based on the ThreeTenBp project.
      * Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
      */

core/js/src/LocalDateTime.kt

@@ -22,6 +22,9 @@ public actual class LocalDateTime internal constructor(internal val value: jtLoc
     public actual constructor(year: Int, month: Month, dayOfMonth: Int, hour: Int, minute: Int, second: Int, nanosecond: Int) :
             this(year, month.number, dayOfMonth, hour, minute, second, nanosecond)
 
+    public actual constructor(date: LocalDate, time: LocalTime) :
+            this(jtLocalDateTime.of(date.value, time.value))
+
     public actual val year: Int get() = value.year().toInt()
     public actual val monthNumber: Int get() = value.monthValue().toInt()
     public actual val month: Month get() = value.month().toMonth()

core/jvm/src/LocalDateTime.kt

@@ -27,6 +27,9 @@ public actual class LocalDateTime internal constructor(internal val value: jtLoc
     public actual constructor(year: Int, month: Month, dayOfMonth: Int, hour: Int, minute: Int, second: Int, nanosecond: Int) :
             this(year, month.number, dayOfMonth, hour, minute, second, nanosecond)
 
+    public actual constructor(date: LocalDate, time: LocalTime) :
+            this(jtLocalDateTime.of(date.value, time.value))
+
     public actual val year: Int get() = value.year
     public actual val monthNumber: Int get() = value.monthValue
     public actual val month: Month get() = value.month

core/native/src/LocalDateTime.kt

@@ -22,8 +22,8 @@ internal val localDateTimeParser: Parser<LocalDateTime>
         }
 
 @Serializable(with = LocalDateTimeIso8601Serializer::class)
-public actual class LocalDateTime internal constructor(
-    public actual val date: LocalDate, public actual val time: LocalTime) : Comparable<LocalDateTime> {
+public actual class LocalDateTime
+public actual constructor(public actual val date: LocalDate, public actual val time: LocalTime) : Comparable<LocalDateTime> {
     public actual companion object {
         public actual fun parse(isoString: String): LocalDateTime =
             localDateTimeParser.parse(isoString)