Add missing Instant converters

Author: koperagen

core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/convert.kt

@@ -7,8 +7,10 @@ import kotlinx.datetime.TimeZone
 import kotlinx.datetime.atStartOfDayIn
 import kotlinx.datetime.atTime
 import kotlinx.datetime.toInstant
+import kotlinx.datetime.toJavaInstant
 import kotlinx.datetime.toJavaLocalDate
 import kotlinx.datetime.toJavaLocalDateTime
+import kotlinx.datetime.toKotlinInstant
 import kotlinx.datetime.toKotlinLocalDate
 import kotlinx.datetime.toKotlinLocalDateTime
 import kotlinx.datetime.toLocalDateTime
@@ -248,9 +250,20 @@ internal fun createConverter(from: KType, to: KType, options: ParserOptions? = n
                 LocalDate::class -> convert<Instant> { it.toLocalDate(defaultTimeZone) }
                 java.time.LocalDateTime::class -> convert<Instant> { it.toLocalDateTime(defaultTimeZone).toJavaLocalDateTime() }
                 java.time.LocalDate::class -> convert<Instant> { it.toLocalDate(defaultTimeZone).toJavaLocalDate() }
+                java.time.Instant::class -> convert<Instant> { it.toJavaInstant() }
                 LocalTime::class -> convert<Instant> { it.toLocalTime(defaultTimeZone) }
                 else -> null
             }
+            java.time.Instant::class -> when (toClass) {
+                Long::class -> convert<java.time.Instant> { it.toEpochMilli() }
+                LocalDateTime::class -> convert<java.time.Instant> { it.toKotlinInstant().toLocalDateTime(defaultTimeZone) }
+                LocalDate::class -> convert<java.time.Instant> { it.toKotlinInstant().toLocalDate(defaultTimeZone) }
+                java.time.LocalDateTime::class -> convert<java.time.Instant> { it.toKotlinInstant().toLocalDateTime(defaultTimeZone).toJavaLocalDateTime() }
+                java.time.LocalDate::class -> convert<java.time.Instant> { it.toKotlinInstant().toLocalDate(defaultTimeZone).toJavaLocalDate() }
+                Instant::class -> convert<java.time.Instant> { it.toKotlinInstant() }
+                LocalTime::class -> convert<java.time.Instant> { it.toKotlinInstant().toLocalTime(defaultTimeZone) }
+                else -> null
+            }
             Float::class -> when (toClass) {
                 Double::class -> convert<Float> { it.toDouble() }
                 Long::class -> convert<Float> { it.roundToLong() }

docs/StardustDocs/topics/convertTo.md

@@ -8,3 +8,20 @@ convertTo<T>()
 ```
 
 Any additional columns will be dropped.
+
+You can provide custom converters and parsers:
+<!---FUN customConverters-->
+
+```kotlin
+class IntClass(val value: Int)
+
+@DataSchema
+class IntSchema(val ints: IntClass)
+
+val df = dataFrameOf("ints")(1, 2, 3)
+df.convertTo<IntSchema> {
+    convert<Int>().with { IntClass(it) }
+}
+```
+
+<!---END-->

tests/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/convert.kt

@@ -1,5 +1,6 @@
 package org.jetbrains.kotlinx.dataframe.api
 
+import io.kotest.assertions.throwables.shouldNotThrow
 import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.matchers.shouldBe
 import kotlinx.datetime.Clock
@@ -137,4 +138,14 @@ class ConvertTests {
 
         col.convertTo<Int?>().hasNulls() shouldBe false
     }
+
+    @Test
+    fun `convert instant`() {
+        println(Clock.System.now().toEpochMilliseconds())
+        val kotlinxInstants = columnOf(Instant.fromEpochMilliseconds(1657283006955))
+        shouldNotThrow<TypeConverterNotFoundException> {
+            val javaInstant = kotlinxInstants.convertTo<java.time.Instant>()
+            javaInstant.convertTo<Instant>() shouldBe kotlinxInstants
+        }
+    }
 }

tests/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/Modify.kt

@@ -2,6 +2,7 @@ package org.jetbrains.kotlinx.dataframe.samples.api
 
 import io.kotest.matchers.shouldBe
 import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.annotations.DataSchema
 import org.jetbrains.kotlinx.dataframe.api.*
 import org.junit.Test
 import java.time.format.DateTimeFormatter
@@ -921,4 +922,19 @@ class Modify : TestBase() {
             .rename { isHappy }.into("isOK")
         // SampleEnd
     }
+
+    @Test
+    fun customConverters() {
+        // SampleStart
+        class IntClass(val value: Int)
+
+        @DataSchema
+        class IntSchema(val ints: IntClass)
+
+        val df = dataFrameOf("ints")(1, 2, 3)
+        df.convertTo<IntSchema> {
+            convert<Int>().with { IntClass(it) }
+        }
+        // SampleEnd
+    }
 }