From 0bab9b8bb41c21181749d55444e3bf99484b47b0 Mon Sep 17 00:00:00 2001
From: Paul Dingemans <paul-dingemans@users.noreply.github.com>
Date: Mon, 4 Sep 2023 19:54:03 +0200
Subject: [PATCH] Do not remove parenthesis after explicit class constructor
 without arguments (#2226)

---
 CHANGELOG.md                                          |  1 +
 .../ruleset/standard/rules/ClassSignatureRule.kt      |  8 +++++++-
 .../ruleset/standard/rules/ClassSignatureRuleTest.kt  | 11 +++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 46e5b91863..f239ee5e9b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -102,6 +102,7 @@ If an `EditorConfigProperty` is defined in a `Rule` that is only provided via a
 * Fix wrapping of multiline postfix expression `multiline-expression-wrapping` [#2183](https://github.com/pinterest/ktlint/issues/2183)
 * Remove registration of class "org.jetbrains.kotlin.com.intellij.treeCopyHandler" as extension point for the compiler as this is not supported in the embedded Kotlin compiler version 1.9. Also remove Ktlint CLI command line flag `disable-kotlin-extension-point`, and parameter `enableKotlinCompilerExtensionPoint` from `KtLintRuleEngine` to disable the kotlin extension point [#2061](https://github.com/pinterest/ktlint/issues/2061)
 * Do not wrap expression after a spread operator `multiline-expression-wrapping` [#2188](https://github.com/pinterest/ktlint/issues/2188)
+* Do not remove parenthesis after explicit constructor keyword when it has no parameters ([#2226](https://github.com/pinterest/ktlint/pull/2226))
 
 ### Changed
 
diff --git a/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRule.kt b/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRule.kt
index aee1bb71e1..153489a50d 100644
--- a/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRule.kt
+++ b/ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRule.kt
@@ -6,6 +6,7 @@ import com.pinterest.ktlint.rule.engine.core.api.ElementType.CLASS
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.CLASS_BODY
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.COLON
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.COMMA
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.CONSTRUCTOR_KEYWORD
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.MODIFIER_LIST
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.PRIMARY_CONSTRUCTOR
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.RPAR
@@ -39,6 +40,7 @@ import com.pinterest.ktlint.rule.engine.core.api.isWhiteSpaceWithNewline
 import com.pinterest.ktlint.rule.engine.core.api.nextCodeLeaf
 import com.pinterest.ktlint.rule.engine.core.api.nextCodeSibling
 import com.pinterest.ktlint.rule.engine.core.api.nextLeaf
+import com.pinterest.ktlint.rule.engine.core.api.prevCodeSibling
 import com.pinterest.ktlint.rule.engine.core.api.prevLeaf
 import com.pinterest.ktlint.rule.engine.core.api.prevSibling
 import com.pinterest.ktlint.rule.engine.core.api.upsertWhitespaceAfterMe
@@ -251,7 +253,11 @@ public class ClassSignatureRule :
         node
             .getPrimaryConstructorParameterListOrNull()
             ?.takeUnless { it.containsComment() }
-            ?.let { parameterList ->
+            ?.takeUnless {
+                // Allow:
+                //     class Foo constructor() { ... }
+                it.prevCodeSibling()?.elementType == CONSTRUCTOR_KEYWORD
+            }?.let { parameterList ->
                 if (!dryRun) {
                     emit(parameterList.startOffset, "No parenthesis expected", true)
                 }
diff --git a/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRuleTest.kt b/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRuleTest.kt
index cc054f425d..85def18e48 100644
--- a/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRuleTest.kt
+++ b/ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/ClassSignatureRuleTest.kt
@@ -1684,6 +1684,17 @@ class ClassSignatureRuleTest {
             ).isFormattedAs(formattedCode)
     }
 
+    @Test
+    fun `Given a class with an explicit constructor not having arguments`() {
+        val code =
+            """
+            class Foo constructor() {
+                fun bar()
+            }
+            """.trimIndent()
+        classSignatureWrappingRuleAssertThat(code).hasNoLintViolations()
+    }
+
     private companion object {
         const val UNEXPECTED_SPACES = "  "
         const val NO_SPACE = ""