fix camelCase

core/api/core.api

@@ -9938,8 +9938,6 @@ public final class org/jetbrains/kotlinx/dataframe/impl/UtilsKt {
 	public static final fun getColumnName (Lkotlin/reflect/KCallable;)Ljava/lang/String;
 	public static final fun getColumnName (Lkotlin/reflect/KFunction;)Ljava/lang/String;
 	public static final fun getColumnName (Lkotlin/reflect/KProperty;)Ljava/lang/String;
-	public static final fun getDELIMITED_STRING_REGEX ()Lkotlin/text/Regex;
-	public static final fun getDELIMITERS_REGEX ()Lkotlin/text/Regex;
 	public static final fun headPlusArray (B[B)[B
 	public static final fun headPlusArray (C[C)[C
 	public static final fun headPlusArray (D[D)[D
@@ -9948,7 +9946,8 @@ public final class org/jetbrains/kotlinx/dataframe/impl/UtilsKt {
 	public static final fun headPlusArray (J[J)[J
 	public static final fun headPlusArray (S[S)[S
 	public static final fun headPlusArray (Z[Z)[Z
-	public static final fun toCamelCaseByDelimiters (Ljava/lang/String;Lkotlin/text/Regex;)Ljava/lang/String;
+	public static final fun toCamelCaseByDelimiters (Ljava/lang/String;Lkotlin/text/Regex;Ljava/lang/String;)Ljava/lang/String;
+	public static synthetic fun toCamelCaseByDelimiters$default (Ljava/lang/String;Lkotlin/text/Regex;Ljava/lang/String;ILjava/lang/Object;)Ljava/lang/String;
 	public static final fun zero (Lkotlin/reflect/KClass;)Ljava/lang/Number;
 	public static final fun zeroOrNull (Lkotlin/reflect/KClass;)Ljava/lang/Number;
 }

core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/rename.kt

@@ -13,8 +13,6 @@ import org.jetbrains.kotlinx.dataframe.columns.ColumnWithPath
 import org.jetbrains.kotlinx.dataframe.columns.FrameColumn
 import org.jetbrains.kotlinx.dataframe.columns.renamedReference
 import org.jetbrains.kotlinx.dataframe.columns.toColumnSet
-import org.jetbrains.kotlinx.dataframe.impl.DELIMITED_STRING_REGEX
-import org.jetbrains.kotlinx.dataframe.impl.DELIMITERS_REGEX
 import org.jetbrains.kotlinx.dataframe.impl.api.renameImpl
 import org.jetbrains.kotlinx.dataframe.impl.columnName
 import org.jetbrains.kotlinx.dataframe.impl.toCamelCaseByDelimiters
@@ -46,23 +44,44 @@ public class RenameClause<T, C>(internal val df: DataFrame<T>, internal val colu
 }
 
 /**
- * ## Rename to camelCase
+ * ## Rename to "camelCase"
+ *
+ * This function renames all columns in this [DataFrame] to the "camelCase" format.
+ *
+ * Removes all delimiters between words and capitalizes each word except the first one.
+ * Adds an underscore between consecutive numbers.
+ * If the string does not contain any letters or numbers, it remains unchanged.
+ *
+ * This function supports converting names from `snake_case`, `PascalCase`, and other delimited formats
+ * into a consistent "camelCase" representation.
  *
- * This function renames all columns to `camelCase` by replacing all [delimiters][DELIMITERS_REGEX]
- * and converting the first char to lowercase.
- * Even [DataFrames][DataFrame] inside [FrameColumns][FrameColumn] are traversed recursively.
+ * [DataFrames][DataFrame] inside [FrameColumns][FrameColumn] are traversed recursively.
+ *
+ * Returns a [DataFrame] with updated column names.
+ *
+ * ### Examples:
+ * ```
+ * "snake_case_name" -> "snakeCaseName"
+ * "PascalCaseName" -> "pascalCaseName"
+ * "doner-case-name" -> "donerCaseName"
+ * "UPPER_CASE_NAME -> upperCaseName"
+ * ```
+ *
+ * @return a [DataFrame] with column names converted to "camelCase" format.
  */
 @Refine
 @Interpretable("RenameToCamelCase")
 public fun <T> DataFrame<T>.renameToCamelCase(): DataFrame<T> =
     // recursively rename all columns written with delimiters or starting with a capital to camel case
     rename {
-        colsAtAnyDepth { it.name() matches DELIMITED_STRING_REGEX || it.name[0].isUpperCase() }
+        colsAtAnyDepth()
     }.toCamelCase()
         // take all frame columns at any depth and call renameToCamelCase() on all dataframes inside
         .update {
             colsAtAnyDepth().colsOf<AnyFrame>()
-        }.with { it.renameToCamelCase() }
+        }.with {
+            it.renameToCamelCase()
+        }
 
 @AccessApiOverload
 public fun <T, C> RenameClause<T, C>.into(vararg newColumns: ColumnReference<*>): DataFrame<T> =
@@ -80,10 +99,27 @@ public fun <T, C> RenameClause<T, C>.into(transform: (ColumnWithPath<C>) -> Stri
     renameImpl(transform)
 
 /**
- * ## Rename to camelCase
+ * ## Rename to "camelCase"
  *
- * Renames the selected columns to `camelCase` by replacing all [delimiters][DELIMITERS_REGEX]
- * and converting the first char to lowercase.
+ * Renames the columns, previously selected with [rename] to "camelCase" format.
+ * All delimiters between words are removed, words are capitalized except for the first one.
+ * Places underscore between numbers.
+ * If the string does not contain any letters or numbers, it remains unchanged.
+ *
+ * Returns a [DataFrame] with updated column names.
+ *
+ * This function supports converting names from `snake_case`, `PascalCase`, and other delimited formats
+ * into a consistent "camelCase" representation.
+ *
+ * ### Examples:
+ * ```
+ * "snake_case_name" -> "snakeCaseName"
+ * "PascalCaseName" -> "pascalCaseName"
+ * "doner-case-name" -> "donerCaseName"
+ * "UPPER_CASE_NAME -> upperCaseName"
+ * ```
+ *
+ * @return a [DataFrame] with column names converted to "camelCase" format.
  */
 @Refine
 @Interpretable("RenameToCamelCaseClause")
@@ -96,15 +132,29 @@ public fun <T, C> RenameClause<T, C>.toCamelCase(): DataFrame<T> = into { it.ren
 /**
  * ## Rename to camelCase
  *
- * Renames this column to `camelCase` by replacing all [delimiters][DELIMITERS_REGEX]
- * and converting the first char to lowercase.
+ * Renames this column to "camelCase" format.
+ * All delimiters between words are removed, words are capitalized except for the first one.
+ * Places underscore between numbers.
+ * If the string does not contain any letters or numbers, it remains unchanged.
+ *
+ * Returns a [ColumnReference] with updated name.
+ *
+ * This function supports converting names from `snake_case`, `PascalCase`, and other delimited formats
+ * into a consistent "camelCase" representation.
+ *
+ * ### Examples:
+ * ```
+ * "snake_case_name" -> "snakeCaseName"
+ * "PascalCaseName" -> "pascalCaseName"
+ * "doner-case-name" -> "donerCaseName"
+ * "UPPER_CASE_NAME -> upperCaseName"
+ * ```
+ * @return a [ColumnReference] with the name converted to "camelCase" format.
  */
 @Suppress("UNCHECKED_CAST")
 public fun <T, C : ColumnReference<T>> C.renameToCamelCase(): C =
     rename(
-        this.name()
-            .toCamelCaseByDelimiters(DELIMITERS_REGEX)
-            .replaceFirstChar { it.lowercaseChar() },
+        this.name().toCamelCaseByDelimiters(),
     ) as C
 
 @Suppress("UNCHECKED_CAST")

core/generated-sources/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/Utils.kt

@@ -337,28 +337,118 @@ internal fun <T : Comparable<T>> T.between(left: T, right: T, includeBoundaries:
         this > left && this < right
     }
 
-private const val DELIMITERS = "[_\\s]"
-public val DELIMITERS_REGEX: Regex = DELIMITERS.toRegex()
-public val DELIMITED_STRING_REGEX: Regex = ".+$DELIMITERS.+".toRegex()
+// Single regex to split words by non-alphanumeric characters, camelCase, and numbers
+internal val CAMEL_DEFAULT_DELIMITERS_REGEX =
+    (
+        "[^\\p{L}0-9]+|(?<=[\\p{Ll}])(?=[\\p{Lu}])|(?<=[\\p{Lu}])" +
+            "(?=[\\p{Lu}][\\p{Ll}])|(?<=\\d)(?=[\\p{L}])|(?<=[\\p{L}])(?=\\d)"
+    )
+        .toRegex()
 
-internal val CAMEL_REGEX = "(?<=[a-zA-Z])[A-Z]".toRegex()
+/**
+ * Converts a string into lowerCamelCase using [delimiters].
+ *
+ * - Splits this string matching given [delimiters] regular expression
+ * (by default, via [CAMEL_DEFAULT_DELIMITERS_REGEX] - any characters that are not letters or digits).
+ * - If the string does not contain any letters or numbers, it remains unchanged.
+ * - Places underscore ("_") between consecutive numbers (that were split before).
+ * - The first word remains in lowercase, and subsequent words are capitalized.
+ *
+ * Default behavior (with [CAMEL_DEFAULT_DELIMITERS_REGEX]):
+ *
+ * ```
+ * "hello_world" -> "helloWorld"
+ * "HelloWorld" -> "helloWorld"
+ * "json.parser.Config" -> "jsonParserConfig"
+ * "my.var_name test" -> "myVarNameTest"
+ * "thirdColumn" -> "thirdColumn"
+ * "someHTMLParser" -> "someHtmlParser"
+ * "RESTApi" -> "restApi"
+ * "OAuth2Token" -> "oAuth2Token"
+ * "GraphQLQuery" -> "graphQlQuery"
+ * "TCP_3_PROTOCOL" -> "tcp3Protocol"
+ * "123hello_world456" -> "123HelloWorld456"
+ * "API_Response_2023" -> "apiResponse2023"
+ * "UPPER_case-LOWER" -> "upperCaseLower"
+ * "12parse34CamelCase" -> "12Parse34CamelCase"
+ * "snake_case_example" -> "snakeCaseExample"
+ * "dot.separated.words" -> "dotSeparatedWords"
+ * "kebab-case-example" -> "kebabCaseExample"
+ * "MIXED_Case_with_123Numbers" -> "mixedCaseWith123Numbers"
+ * "___!!!___" -> "___!!!___"
+ * "1000.2000.3000" -> "1000_2000_3000"
+ * "UPPERCASE" -> "uppercase"
+ * "alreadyCamelCased" -> "alreadyCamelCased"
+ * "justNumbers123" -> "justNumbers123"
+ * "Just_Special$Chars!!" -> "justSpecialChars"
+ * "singleword" -> "singleword"
+ * "word_with_underscores_and-dashes" -> "wordWithUnderscoresAndDashes"
+ * "10-20-aa" -> "10_20Aa"
+ * ```
+ *
+ * @return the formatted string in lowerCamelCase.
+ */
+public fun String.toCamelCaseByDelimiters(
+    delimiters: Regex = CAMEL_DEFAULT_DELIMITERS_REGEX,
+    numberSeparator: String = "_",
+): String =
+    if (!this.any { it.isLetter() || it.isDigit() }) {
+        this // If the string has no letters, return it unchanged
+    } else {
+        split(delimiters)
+            .filter { it.isNotBlank() }
+            .map { it.lowercase() }
+            .joinNumbers(numberSeparator)
+            .joinToCamelCaseString()
+    }
+
+/**
+ * Joins consecutive numbers in a list with the given [separator].
+ * Assumes that all numbers and strings are separated (after splitting via [CAMEL_DEFAULT_DELIMITERS_REGEX]).
+ */
+private fun List<String>.joinNumbers(separator: CharSequence): List<String> {
+    val result = mutableListOf<String>()
+    var i = 0
+
+    while (i < this.size) {
+        val current = this[i]
+        if (current.all { it.isDigit() }) { // Check if the current element is a number
+            val numberGroup = mutableListOf(current)
+            while (i + 1 < this.size && this[i + 1].all { it.isDigit() }) {
+                numberGroup.add(this[i + 1])
+                i++
+            }
+            result.add(numberGroup.joinToString(separator)) // Join consecutive numbers with "_"
+        } else {
+            result.add(current)
+        }
+        i++
+    }
+    return result
+}
 
-public fun String.toCamelCaseByDelimiters(delimiters: Regex): String = split(delimiters).joinToCamelCaseString()
+/**
+ * Joins a list of words into lowerCamelCase format.
+ * - The first word is converted to lowercase.
+ * - Subsequent words start with an uppercase letter.
+ */
+private fun List<String>.joinToCamelCaseString(): String =
+    mapIndexed { index, word ->
+        if (index == 0) word.lowercase() else word.replaceFirstChar { it.uppercaseChar() }
+    }.joinToString("")
+
+internal val CAMEL_LETTERS_REGEX = "(?<=[a-zA-Z])[A-Z]".toRegex()
 
 internal fun String.toSnakeCase(): String =
     if ("[A-Z_]+".toRegex().matches(this)) {
         this
     } else {
-        CAMEL_REGEX
+        CAMEL_LETTERS_REGEX
             .replace(this) { "_${it.value}" }
             .replace(" ", "_")
             .lowercase()
     }
 
-internal fun List<String>.joinToCamelCaseString(): String =
-    joinToString(separator = "") { it.replaceFirstChar { it.uppercaseChar() } }
-        .replaceFirstChar { it.lowercaseChar() }
-
 /** Returns `true` if this callable is a getter-like function.
  *
  * A callable is considered getter-like if it is either a property getter,

core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/rename.kt

@@ -179,6 +179,13 @@ class RenameToCamelCaseTests {
         df.getColumnGroup("testName").columnNames() shouldBe listOf("anotherName")
     }
 
+    @Test
+    fun `uppercase names`() {
+        val originalDf = dataFrameOf("ID", "ITEM", "ORDER_DATE")(1, "TOY", "02.03.2009")
+        val renamedDf = originalDf.renameToCamelCase()
+        renamedDf.columnNames() shouldBe listOf("id", "item", "orderDate")
+    }
+
     @Test
     fun `doubly nested row`() {
         val doublyNestedColumnGroup = dataFrameOf("test_name")(

core/generated-sources/src/test/kotlin/org/jetbrains/kotlinx/dataframe/impl/ToCamelCase.kt

@@ -0,0 +1,86 @@
+package org.jetbrains.kotlinx.dataframe.impl
+
+import io.kotest.matchers.shouldBe
+import org.junit.Test
+
+class ToCamelCase {
+    @Test
+    fun defaultDelimitersSimpleUseCases() {
+        val testCases = listOf(
+            "hello_world",
+            "HelloWorld",
+            "json.parser.Config",
+            "my.var_name test",
+            "thirdColumn",
+            "someHTMLParser",
+            "RESTApi",
+            "OAuth2Token",
+            "GraphQLQuery",
+            "TCP_3_PROTOCOL",
+            "123hello_world456",
+            "API_Response_2023",
+            "UPPER_case-LOWER",
+            "12parse34CamelCase",
+            "snake_case_example",
+            "dot.separated.words",
+            "kebab-case-example",
+            "MIXED_Case_with_123Numbers",
+            "___!!!___",
+            "1000.2000.3000",
+            "UPPERCASE",
+            "alreadyCamelCased",
+            "justNumbers123",
+            "Just_Special\$Chars!!",
+            "singleword",
+            "word_with_underscores_and-dashes",
+            "10-20-aa",
+            "ROOM_1.11",
+        )
+        val expected = listOf(
+            "helloWorld",
+            "helloWorld",
+            "jsonParserConfig",
+            "myVarNameTest",
+            "thirdColumn",
+            "someHtmlParser",
+            "restApi",
+            "oAuth2Token",
+            "graphQlQuery",
+            "tcp3Protocol",
+            "123HelloWorld456",
+            "apiResponse2023",
+            "upperCaseLower",
+            "12Parse34CamelCase",
+            "snakeCaseExample",
+            "dotSeparatedWords",
+            "kebabCaseExample",
+            "mixedCaseWith123Numbers",
+            "___!!!___",
+            "1000_2000_3000",
+            "uppercase",
+            "alreadyCamelCased",
+            "justNumbers123",
+            "justSpecialChars",
+            "singleword",
+            "wordWithUnderscoresAndDashes",
+            "10_20Aa",
+            "room1_11",
+        )
+
+        testCases.zip(expected).forEach { (input, expected) ->
+            input.toCamelCaseByDelimiters() shouldBe expected
+        }
+    }
+
+    @Test
+    fun specialCharacters() {
+        "música_lírica".toCamelCaseByDelimiters() shouldBe "músicaLírica"
+        "тут был Андрей".toCamelCaseByDelimiters() shouldBe "тутБылАндрей"
+        "汉字_拼音".toCamelCaseByDelimiters() shouldBe "汉字拼音"
+        "X Æ A-12 34".toCamelCaseByDelimiters() shouldBe "xÆA12_34"
+        "kæt_wɪð_æk!t".toCamelCaseByDelimiters() shouldBe "kætWɪðÆkT"
+        "Gëëxplodeerd,_of_geïntegreerd?".toCamelCaseByDelimiters() shouldBe "gëëxplodeerdOfGeïntegreerd"
+        "Äüßergewöhnlich_könnte_flüssig_sein,_aber_wie_öfter?".toCamelCaseByDelimiters() shouldBe
+            "äüßergewöhnlichKönnteFlüssigSeinAberWieÖfter"
+    }
+}