From cd3747fa5cc2831d4050a74e0dd0a2c3e04e7609 Mon Sep 17 00:00:00 2001
From: Jolan Rensen <jolan.rensen@jetbrains.com>
Date: Tue, 30 Jul 2024 17:00:13 +0200
Subject: [PATCH 1/3] small QoL improvement to the value/type check of
 DataColumnImpl

---
 .../jetbrains/kotlinx/dataframe/impl/columns/DataColumnImpl.kt | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/DataColumnImpl.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/DataColumnImpl.kt
index aef3f08b83..eac43db02b 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/DataColumnImpl.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/columns/DataColumnImpl.kt
@@ -5,6 +5,7 @@ import org.jetbrains.kotlinx.dataframe.DataColumn
 import org.jetbrains.kotlinx.dataframe.api.dataFrameOf
 import org.jetbrains.kotlinx.dataframe.impl.isArray
 import org.jetbrains.kotlinx.dataframe.impl.isPrimitiveArray
+import org.jetbrains.kotlinx.dataframe.kind
 import kotlin.reflect.KClass
 import kotlin.reflect.KType
 import kotlin.reflect.full.isSubclassOf
@@ -37,7 +38,7 @@ internal abstract class DataColumnImpl<T>(
         if (BuildConfig.DEBUG) {
             require(values.all { it matches type }) {
                 val types = values.map { if (it == null) "Nothing?" else it!!::class.simpleName }.distinct()
-                "Values of column '$name' have types '$types' which are not compatible given with column type '$type'"
+                "Values of $kind '$name' have types '$types' which are not compatible given with column type '$type'"
             }
         }
     }

From 3037a978d13f211401bec79e8ae17fa99a658cf0 Mon Sep 17 00:00:00 2001
From: Jolan Rensen <jolan.rensen@jetbrains.com>
Date: Tue, 30 Jul 2024 17:01:34 +0200
Subject: [PATCH 2/3] small fix for two failing tests in #713, where in
 implodeImpl a temporary column was created with nulls in a FrameColumn

---
 .../jetbrains/kotlinx/dataframe/impl/api/implode.kt    | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/implode.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/implode.kt
index 84b2446d7b..988f7bc3b9 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/implode.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/implode.kt
@@ -30,8 +30,14 @@ internal fun <T, C> DataFrame<T>.implodeImpl(dropNA: Boolean = false, columns: C
                     first = false
                     value
                 } else {
-                    null
+                    // these rows will not be taken into account,
+                    // but we cannot leave them empty, as `map` creates a full column
+                    when (column.kind()) {
+                        ColumnKind.Value -> emptyList<Any?>()
+                        ColumnKind.Group -> DataFrame.empty()
+                        ColumnKind.Frame -> emptyList<AnyFrame>()
+                    }
                 }
             }
-        }[0..0]
+        }[0..0] // takes only the first row
     }.concat()

From 23046d82fbf28a355d6e916cd343e780b86b835f Mon Sep 17 00:00:00 2001
From: Jolan Rensen <jolan.rensen@jetbrains.com>
Date: Wed, 31 Jul 2024 14:31:07 +0200
Subject: [PATCH 3/3] small fix for one failing test in #713, where
 GroupBy.aggregate { this into "" } would break typing

---
 .../impl/aggregation/GroupByReceiverImpl.kt       | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/aggregation/GroupByReceiverImpl.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/aggregation/GroupByReceiverImpl.kt
index 171403c4f8..5272accd19 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/aggregation/GroupByReceiverImpl.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/aggregation/GroupByReceiverImpl.kt
@@ -14,6 +14,7 @@ import org.jetbrains.kotlinx.dataframe.columns.ValueColumn
 import org.jetbrains.kotlinx.dataframe.columns.shortPath
 import org.jetbrains.kotlinx.dataframe.impl.aggregation.receivers.AggregateInternalDsl
 import org.jetbrains.kotlinx.dataframe.impl.api.AggregatedPivot
+import org.jetbrains.kotlinx.dataframe.impl.createStarProjectedType
 import org.jetbrains.kotlinx.dataframe.impl.createTypeWithArgument
 import org.jetbrains.kotlinx.dataframe.impl.getListType
 import kotlin.reflect.KType
@@ -118,7 +119,19 @@ internal class GroupByReceiverImpl<T>(override val df: DataFrame<T>, override va
                 pivot.aggregator.values.clear()
             }
 
-            is AggregateInternalDsl<*> -> yield(value.copy(value = value.value.df))
+            is AggregateInternalDsl<*> -> {
+                // Attempt to create DataFrame<Type> from AggregateInternalDsl<Type>
+                val dfType = value.type?.arguments?.firstOrNull()?.type
+                    ?.let { DataFrame::class.createTypeWithArgument(it) }
+                    ?: DataFrame::class.createStarProjectedType(nullable = false)
+
+                yield(
+                    value.copy(
+                        value = value.value.df,
+                        type = dfType,
+                    ),
+                )
+            }
 
             else -> values.add(value)
         }