feat(lapis): also handle SILO returning arrow date values

lapis/src/main/kotlin/org/genspectrum/lapis/silo/ArrowRowConverter.kt

@@ -10,6 +10,7 @@ import com.fasterxml.jackson.databind.node.NullNode
 import com.fasterxml.jackson.databind.node.TextNode
 import org.apache.arrow.vector.BigIntVector
 import org.apache.arrow.vector.BitVector
+import org.apache.arrow.vector.DateDayVector
 import org.apache.arrow.vector.Float4Vector
 import org.apache.arrow.vector.Float8Vector
 import org.apache.arrow.vector.IntVector
@@ -188,6 +189,7 @@ private fun VectorSchemaRoot.fieldValueAsJsonNode(
         is Float8Vector -> DoubleNode(vector.get(rowIndex))
         is Float4Vector -> FloatNode(vector.get(rowIndex))
         is BitVector -> BooleanNode.valueOf(vector.get(rowIndex) != 0)
+        is DateDayVector -> TextNode(java.time.LocalDate.ofEpochDay(vector.get(rowIndex).toLong()).toString())
         else -> TextNode(vector.getObject(rowIndex)?.toString() ?: "")
     }
 }

lapis/src/test/kotlin/org/genspectrum/lapis/silo/ArrowTestHelper.kt

@@ -3,17 +3,20 @@ package org.genspectrum.lapis.silo
 import org.apache.arrow.memory.RootAllocator
 import org.apache.arrow.vector.BigIntVector
 import org.apache.arrow.vector.BitVector
+import org.apache.arrow.vector.DateDayVector
 import org.apache.arrow.vector.Float8Vector
 import org.apache.arrow.vector.IntVector
 import org.apache.arrow.vector.VarCharVector
 import org.apache.arrow.vector.VectorSchemaRoot
 import org.apache.arrow.vector.ipc.ArrowStreamWriter
+import org.apache.arrow.vector.types.DateUnit
 import org.apache.arrow.vector.types.pojo.ArrowType
 import org.apache.arrow.vector.types.pojo.Field
 import org.apache.arrow.vector.types.pojo.FieldType
 import org.apache.arrow.vector.types.pojo.Schema
 import java.io.ByteArrayOutputStream
 import java.nio.channels.Channels
+import java.time.LocalDate
 
 /**
  * Builds an Arrow IPC stream byte array from [rows] using the given builder.
@@ -51,6 +54,8 @@ fun buildArrowIpcStream(rows: List<Map<String, Any?>>): ByteArray {
 
             is Boolean -> Field(name, FieldType.nullable(ArrowType.Bool()), null)
 
+            is LocalDate -> Field(name, FieldType.nullable(ArrowType.Date(DateUnit.DAY)), null)
+
             // Note: null values (and any unrecognized types) are typed as Utf8.
             // If the first row has null for a column that later rows fill with a typed value (e.g. Int, Long),
             // the column will be inferred as Utf8 and the converter will throw a cast error at runtime.
@@ -101,6 +106,14 @@ fun buildArrowIpcStream(rows: List<Map<String, Any?>>): ByteArray {
                     }
                 }
 
+                is DateDayVector -> {
+                    if (value == null) {
+                        vector.setNull(rowIdx)
+                    } else {
+                        vector.set(rowIdx, (value as LocalDate).toEpochDay().toInt())
+                    }
+                }
+
                 is VarCharVector -> {
                     if (value == null) {
                         vector.setNull(rowIdx)

lapis/src/test/kotlin/org/genspectrum/lapis/silo/SiloClientTest.kt

@@ -41,6 +41,7 @@ import org.mockserver.model.MediaType
 import org.mockserver.model.MediaType.parse
 import org.springframework.beans.factory.annotation.Autowired
 import org.springframework.boot.test.context.SpringBootTest
+import java.time.LocalDate
 
 private const val MOCK_SERVER_PORT = 1080
 
@@ -295,6 +296,36 @@ class SiloClientTest(
         )
     }
 
+    @Test
+    fun `GIVEN server returns date32 column THEN dates are converted to ISO-8601 strings and nulls remain null`() {
+        expectQueryRequestAndRespondWith(
+            response()
+                .withContentType(parse(ARROW_STREAM_MEDIA_TYPE))
+                .withBody(
+                    buildArrowIpcStream(
+                        listOf(
+                            mapOf("date" to LocalDate.of(2021, 2, 23), "label" to "A"),
+                            mapOf("date" to LocalDate.of(2021, 3, 19), "label" to "B"),
+                            mapOf("date" to null, "label" to "C"),
+                        ),
+                    ),
+                ),
+        )
+
+        val query = SiloQuery(SiloAction.details(), StringEquals("theColumn", "theValue"))
+        val result = sendQuery(query)
+
+        assertThat(result, hasSize(3))
+        assertThat(
+            result,
+            containsInAnyOrder(
+                DetailsData(mapOf("date" to TextNode("2021-02-23"), "label" to TextNode("A"))),
+                DetailsData(mapOf("date" to TextNode("2021-03-19"), "label" to TextNode("B"))),
+                DetailsData(mapOf("date" to NullNode.instance, "label" to TextNode("C"))),
+            ),
+        )
+    }
+
     @Test
     fun `GIVEN server returns most recent common ancestor response THEN response can be deserialized`() {
         expectQueryRequestAndRespondWith(