Add implicit conversions from java.time classes to plotly LocalDateTime (#178)

Author: tmccarthy

core/js/src/main/scala/plotly/element/PlotlyJavaTimeConversions.scala

@@ -0,0 +1,5 @@
+package plotly.element
+
+trait PlotlyJavaTimeConversions {
+  // Empty since the java.time classes are not available in ScalaJS
+}

core/jvm/src/main/scala/plotly/element/PlotlyJavaTimeConversions.scala

@@ -0,0 +1,40 @@
+package plotly.element
+
+import java.time._
+import plotly.element.{LocalDateTime => PlotlyLocalDateTime}
+
+trait PlotlyJavaTimeConversions {
+
+  implicit def fromJavaLocalDateTime(javaLocalDateTime: java.time.LocalDateTime): PlotlyLocalDateTime =
+    PlotlyLocalDateTime(
+      javaLocalDateTime.getYear,
+      javaLocalDateTime.getMonthValue,
+      javaLocalDateTime.getDayOfMonth,
+      javaLocalDateTime.getHour,
+      javaLocalDateTime.getMinute,
+      javaLocalDateTime.getSecond,
+    )
+
+  implicit def fromJavaInstant(javaInstant: Instant): PlotlyLocalDateTime =
+    fromJavaLocalDateTime(javaInstant.atOffset(ZoneOffset.UTC).toLocalDateTime)
+
+  implicit def fromJavaLocalDate(javaLocalDate: LocalDate): PlotlyLocalDateTime =
+    fromJavaLocalDateTime(javaLocalDate.atStartOfDay)
+
+  /**
+    * Implicit conversions in this object convert to `plotly.element.LocalDateTime` by simply dropping timezone/offset
+    * information. This can lead to unexpected behaviour, particularly for datasets with varying offsets and timezones.
+    * It will generally be safer to convert your data to `java.time.LocalDateTime` in the appropriate timezone/offset,
+    * and then use the `PlotlyJavaTimeConversions.fromJavaLocalDateTime` implicit conversion.
+    */
+  object UnsafeImplicitConversions {
+
+    implicit def fromJavaOffsetDateTime(javaOffsetDateTime: OffsetDateTime): PlotlyLocalDateTime =
+      fromJavaLocalDateTime(javaOffsetDateTime.toLocalDateTime)
+
+    implicit def fromJavaZonedDateTime(javaZonedDateTime: ZonedDateTime): PlotlyLocalDateTime =
+      fromJavaLocalDateTime(javaZonedDateTime.toLocalDateTime)
+
+  }
+
+}

core/shared/src/main/scala/plotly/element/LocalDateTime.scala

@@ -16,7 +16,7 @@ import scala.util.Try
     f"$year-$month%02d-$dayOfMonth%02d $hour%02d:$minute%02d:$second%02d"
 }
 
-object LocalDateTime {
+object LocalDateTime extends PlotlyJavaTimeConversions {
 
   private object IntStr {
     def unapply(s: String): Option[Int] =

tests/src/test/scala/plotly/element/LocalDateTimeTests.scala

@@ -0,0 +1,44 @@
+package plotly.element
+
+import org.scalatest.FlatSpec
+import plotly.element.LocalDateTime.UnsafeImplicitConversions._
+import plotly.element.{LocalDateTime => PlotlyLocalDateTime}
+
+class LocalDateTimeTests extends FlatSpec {
+
+  "JavaTime conversions" should "convert java.time.LocalDateTime to Plotly LocalDateTime" in {
+    val javaLocalDateTime = java.time.LocalDateTime.parse("2020-04-18T14:52:52")
+    val plotlyLocalDateTime = PlotlyLocalDateTime(2020, 4, 18, 14, 52, 52)
+
+    assert((javaLocalDateTime: PlotlyLocalDateTime) === plotlyLocalDateTime)
+  }
+
+  it should "convert java.time.Instant to Plotly LocalDateTime using UTC" in {
+    val javaInstant = java.time.Instant.parse("2020-04-18T14:52:52Z")
+    val plotlyLocalDateTime = PlotlyLocalDateTime(2020, 4, 18, 14, 52, 52)
+
+    assert((javaInstant: PlotlyLocalDateTime) === plotlyLocalDateTime)
+  }
+
+  it should "convert java.time.OffsetDateTime to Plotly LocalDateTime" in {
+    val javaOffsetDateTime = java.time.OffsetDateTime.parse("2020-04-18T14:52:52+10:00")
+    val plotlyLocalDateTime = PlotlyLocalDateTime(2020, 4, 18, 14, 52, 52)
+
+    assert((javaOffsetDateTime: PlotlyLocalDateTime) === plotlyLocalDateTime)
+  }
+
+  it should "convert java.time.ZonedDateTime to Plotly LocalDateTime" in {
+    val javaOffsetDateTime = java.time.ZonedDateTime.parse("2020-04-18T14:52:52+10:00[Australia/Melbourne]")
+    val plotlyLocalDateTime = PlotlyLocalDateTime(2020, 4, 18, 14, 52, 52)
+
+    assert((javaOffsetDateTime: PlotlyLocalDateTime) === plotlyLocalDateTime)
+  }
+
+  it should "convert java.time.LocalDate to Plotly LocalDateTime" in {
+    val javaLocalDate = java.time.LocalDate.parse("2020-04-18")
+    val plotlyLocalDateTime = PlotlyLocalDateTime(2020, 4, 18, 0, 0, 0)
+
+    assert((javaLocalDate: PlotlyLocalDateTime) === plotlyLocalDateTime)
+  }
+
+}