Allow comment before parameter list in function literal (`function-li…

…teral`) (#2894) Merging an EOL comment before the parameter list with the actual parameter list results in code that no longer compiles. Closes #2850
pinterest · Dec 3, 2024 · f4cb520 · f4cb520
1 parent 5cb8c49
commit f4cb520
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Showing 2 changed files with 31 additions and 2 deletions.
diff --git a/...andard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionLiteralRule.kt b/...andard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionLiteralRule.kt
@@ -49,6 +49,7 @@ import com.pinterest.ktlint.rule.engine.core.api.upsertWhitespaceBeforeMe
 import com.pinterest.ktlint.ruleset.standard.StandardRule
 import io.github.oshai.kotlinlogging.KotlinLogging
 import org.jetbrains.kotlin.com.intellij.lang.ASTNode
+import org.jetbrains.kotlin.psi.psiUtil.siblings
 
 private val LOGGER = KotlinLogging.logger {}.initKtLintKLogger()
 
@@ -343,8 +344,8 @@ public class FunctionLiteralRule :
     ) {
         require(parameterList.elementType == VALUE_PARAMETER_LIST)
         parameterList
-            .prevSibling { it.isWhiteSpace() }
-            ?.takeIf { it.isWhiteSpaceWithNewline() }
+            .takeUnless { it.isPrecededByComment() }
+            ?.prevSibling { it.isWhiteSpaceWithNewline() }
             ?.let { whitespaceBeforeParameterList ->
                 emit(parameterList.startOffset, "No newline expected before parameter", true)
                     .ifAutocorrectAllowed {
@@ -362,6 +363,8 @@ public class FunctionLiteralRule :
             }
     }
 
+    private fun ASTNode.isPrecededByComment() = siblings(forward = false).any { it.isPartOfComment() }
+
     private fun visitArrow(
         arrow: ASTNode,
         emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> AutocorrectDecision,

diff --git a/...rd/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionLiteralRuleTest.kt b/...rd/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionLiteralRuleTest.kt
@@ -597,4 +597,30 @@ class FunctionLiteralRuleTest {
                 LintViolation(4, 7, "Arrow is redundant when parameter list is empty"),
             ).isFormattedAs(formattedCode)
     }
+
+    @Test
+    fun `Issue 2850 - Given function literal with a comment before the parameter list which contains a redundant parameter then do remove the redundant parameter but keep the comment`() {
+        val code =
+            """
+            val foo1 =
+                {
+                    // some comment
+                    foo: String -> "foo = " + foo
+                }
+            val foo2 =
+                { // some comment
+                    foo: String -> "foo = " + foo
+                }
+            val foo3 =
+                {
+                    /* some comment */
+                    foo: String -> "foo = " + foo
+                }
+            val foo4 =
+                { /* some comment */
+                    foo: String -> "foo = " + foo
+                }
+            """.trimIndent()
+        functionLiteralRuleAssertThat(code).hasNoLintViolations()
+    }
 }