From 083c902a7042e7fb97581c3f15f72a7cfb4e5f0f Mon Sep 17 00:00:00 2001
From: Jolan Rensen <jolan.rensen@jetbrains.com>
Date: Mon, 14 Oct 2024 12:30:44 +0200
Subject: [PATCH 1/2] change default flatten parent-child separator to "_"

---
 .../jetbrains/kotlinx/dataframe/api/flatten.kt   | 16 ++++++++++------
 .../kotlinx/dataframe/impl/api/flatten.kt        |  3 ++-
 .../jetbrains/kotlinx/dataframe/api/flatten.kt   |  2 +-
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
index 07102bac18..f0fbe77cde 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
@@ -9,37 +9,41 @@ import org.jetbrains.kotlinx.dataframe.columns.toColumnSet
 import org.jetbrains.kotlinx.dataframe.impl.api.flattenImpl
 import kotlin.reflect.KProperty
 
+public const val FLATTEN_DEFAULT_SEPARATOR: String = "_"
+
 // region DataFrame
 
 @Refine
 @Interpretable("FlattenDefault")
-public fun <T> DataFrame<T>.flatten(keepParentNameForColumns: Boolean = false, separator: String = "."): DataFrame<T> =
-    flatten(keepParentNameForColumns, separator) { all() }
+public fun <T> DataFrame<T>.flatten(
+    keepParentNameForColumns: Boolean = false,
+    separator: String = FLATTEN_DEFAULT_SEPARATOR,
+): DataFrame<T> = flatten(keepParentNameForColumns, separator) { all() }
 
 @Refine
 @Interpretable("Flatten0")
 public fun <T, C> DataFrame<T>.flatten(
     keepParentNameForColumns: Boolean = false,
-    separator: String = ".",
+    separator: String = FLATTEN_DEFAULT_SEPARATOR,
     columns: ColumnsSelector<T, C>,
 ): DataFrame<T> = flattenImpl(columns, keepParentNameForColumns, separator)
 
 public fun <T> DataFrame<T>.flatten(
     vararg columns: String,
     keepParentNameForColumns: Boolean = false,
-    separator: String = ".",
+    separator: String = FLATTEN_DEFAULT_SEPARATOR,
 ): DataFrame<T> = flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }
 
 public fun <T, C> DataFrame<T>.flatten(
     vararg columns: ColumnReference<C>,
     keepParentNameForColumns: Boolean = false,
-    separator: String = ".",
+    separator: String = FLATTEN_DEFAULT_SEPARATOR,
 ): DataFrame<T> = flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }
 
 public fun <T, C> DataFrame<T>.flatten(
     vararg columns: KProperty<C>,
     keepParentNameForColumns: Boolean = false,
-    separator: String = ".",
+    separator: String = FLATTEN_DEFAULT_SEPARATOR,
 ): DataFrame<T> = flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }
 
 // endregion
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt
index 25f8f4c415..1d963d6c66 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt
@@ -2,6 +2,7 @@ package org.jetbrains.kotlinx.dataframe.impl.api
 
 import org.jetbrains.kotlinx.dataframe.ColumnsSelector
 import org.jetbrains.kotlinx.dataframe.DataFrame
+import org.jetbrains.kotlinx.dataframe.api.FLATTEN_DEFAULT_SEPARATOR
 import org.jetbrains.kotlinx.dataframe.api.asColumnGroup
 import org.jetbrains.kotlinx.dataframe.api.getColumnsWithPaths
 import org.jetbrains.kotlinx.dataframe.api.into
@@ -15,7 +16,7 @@ import org.jetbrains.kotlinx.dataframe.impl.columns.toColumnSet
 internal fun <T, C> DataFrame<T>.flattenImpl(
     columns: ColumnsSelector<T, C>,
     keepParentNameForColumns: Boolean = false,
-    separator: String = ".",
+    separator: String = FLATTEN_DEFAULT_SEPARATOR,
 ): DataFrame<T> {
     val rootColumns = getColumnsWithPaths {
         columns.toColumnSet().filter { it.isColumnGroup() }.simplify()
diff --git a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
index 6dcd4a93d0..aa457c95be 100644
--- a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
+++ b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
@@ -98,7 +98,7 @@ class FlattenTests {
 
         aggregate
             .flatten(keepParentNameForColumns = true)
-            .columnNames() shouldBe listOf("city", "mean.age", "mean.weight", "std.age", "std.weight")
+            .columnNames() shouldBe listOf("city", "mean_age", "mean_weight", "std_age", "std_weight")
 
         aggregate
             .flatten(keepParentNameForColumns = true, separator = "_happy_separator_")

From fbcb8ff02f7716fda43ccc6a115b58ba503e1f9b Mon Sep 17 00:00:00 2001
From: Jolan Rensen <jolan.rensen@jetbrains.com>
Date: Tue, 15 Oct 2024 17:39:56 +0200
Subject: [PATCH 2/2] inlined flatten separator arguments

---
 .../jetbrains/kotlinx/dataframe/api/flatten.kt   | 16 ++++++----------
 .../kotlinx/dataframe/impl/api/flatten.kt        |  3 +--
 2 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
index f0fbe77cde..7a9ede21de 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/flatten.kt
@@ -9,41 +9,37 @@ import org.jetbrains.kotlinx.dataframe.columns.toColumnSet
 import org.jetbrains.kotlinx.dataframe.impl.api.flattenImpl
 import kotlin.reflect.KProperty
 
-public const val FLATTEN_DEFAULT_SEPARATOR: String = "_"
-
 // region DataFrame
 
 @Refine
 @Interpretable("FlattenDefault")
-public fun <T> DataFrame<T>.flatten(
-    keepParentNameForColumns: Boolean = false,
-    separator: String = FLATTEN_DEFAULT_SEPARATOR,
-): DataFrame<T> = flatten(keepParentNameForColumns, separator) { all() }
+public fun <T> DataFrame<T>.flatten(keepParentNameForColumns: Boolean = false, separator: String = "_"): DataFrame<T> =
+    flatten(keepParentNameForColumns, separator) { all() }
 
 @Refine
 @Interpretable("Flatten0")
 public fun <T, C> DataFrame<T>.flatten(
     keepParentNameForColumns: Boolean = false,
-    separator: String = FLATTEN_DEFAULT_SEPARATOR,
+    separator: String = "_",
     columns: ColumnsSelector<T, C>,
 ): DataFrame<T> = flattenImpl(columns, keepParentNameForColumns, separator)
 
 public fun <T> DataFrame<T>.flatten(
     vararg columns: String,
     keepParentNameForColumns: Boolean = false,
-    separator: String = FLATTEN_DEFAULT_SEPARATOR,
+    separator: String = "_",
 ): DataFrame<T> = flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }
 
 public fun <T, C> DataFrame<T>.flatten(
     vararg columns: ColumnReference<C>,
     keepParentNameForColumns: Boolean = false,
-    separator: String = FLATTEN_DEFAULT_SEPARATOR,
+    separator: String = "_",
 ): DataFrame<T> = flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }
 
 public fun <T, C> DataFrame<T>.flatten(
     vararg columns: KProperty<C>,
     keepParentNameForColumns: Boolean = false,
-    separator: String = FLATTEN_DEFAULT_SEPARATOR,
+    separator: String = "_",
 ): DataFrame<T> = flatten(keepParentNameForColumns, separator) { columns.toColumnSet() }
 
 // endregion
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt
index 1d963d6c66..bd692ef2fc 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/api/flatten.kt
@@ -2,7 +2,6 @@ package org.jetbrains.kotlinx.dataframe.impl.api
 
 import org.jetbrains.kotlinx.dataframe.ColumnsSelector
 import org.jetbrains.kotlinx.dataframe.DataFrame
-import org.jetbrains.kotlinx.dataframe.api.FLATTEN_DEFAULT_SEPARATOR
 import org.jetbrains.kotlinx.dataframe.api.asColumnGroup
 import org.jetbrains.kotlinx.dataframe.api.getColumnsWithPaths
 import org.jetbrains.kotlinx.dataframe.api.into
@@ -16,7 +15,7 @@ import org.jetbrains.kotlinx.dataframe.impl.columns.toColumnSet
 internal fun <T, C> DataFrame<T>.flattenImpl(
     columns: ColumnsSelector<T, C>,
     keepParentNameForColumns: Boolean = false,
-    separator: String = FLATTEN_DEFAULT_SEPARATOR,
+    separator: String = "_",
 ): DataFrame<T> {
     val rootColumns = getColumnsWithPaths {
         columns.toColumnSet().filter { it.isColumnGroup() }.simplify()