Ignore override of function in rule function-naming

CHANGELOG.md

@@ -14,6 +14,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 * Fix indent of multiline object declaration inside class `indent` [#2257](https://github.com/pinterest/ktlint/issue/2257)
 * Ignore anonymous function in rule `function-naming` [#2260](https://github.com/pinterest/ktlint/issue/2260)
 * Do not force blank line before function in right hand side of assignment `blank-line-before-declaration` [#2260](https://github.com/pinterest/ktlint/issue/2260)
+* Ignore override of function in rule `function-naming` [#2271](https://github.com/pinterest/ktlint/issue/2271)
 * Do not replace function body having a return statement only in case the return statement contains an intermediate exit point 'function-expression-body' [#2269](https://github.com/pinterest/ktlint/issue/2269)
 
 ### Changed

ktlint-ruleset-standard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionNamingRule.kt

@@ -4,11 +4,14 @@ import com.pinterest.ktlint.rule.engine.core.api.ElementType.FUN
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.FUN_KEYWORD
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.IDENTIFIER
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.IMPORT_DIRECTIVE
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.MODIFIER_LIST
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.OVERRIDE_KEYWORD
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.VALUE_PARAMETER_LIST
 import com.pinterest.ktlint.rule.engine.core.api.RuleId
 import com.pinterest.ktlint.rule.engine.core.api.SinceKtlint
 import com.pinterest.ktlint.rule.engine.core.api.SinceKtlint.Status.EXPERIMENTAL
 import com.pinterest.ktlint.rule.engine.core.api.SinceKtlint.Status.STABLE
+import com.pinterest.ktlint.rule.engine.core.api.children
 import com.pinterest.ktlint.rule.engine.core.api.nextCodeSibling
 import com.pinterest.ktlint.ruleset.standard.StandardRule
 import com.pinterest.ktlint.ruleset.standard.rules.internal.regExIgnoringDiacriticsAndStrokesOnLetters
@@ -47,7 +50,8 @@ public class FunctionNamingRule : StandardRule("function-naming") {
                 node.isFactoryMethod() ||
                     node.isTestMethod() ||
                     node.hasValidFunctionName() ||
-                    node.isAnonymousFunction()
+                    node.isAnonymousFunction() ||
+                    node.isOverrideFunction()
             }?.let {
                 val identifierOffset =
                     node
@@ -86,6 +90,17 @@ public class FunctionNamingRule : StandardRule("function-naming") {
                 ?.nextCodeSibling()
                 ?.elementType
 
+    /*
+     * A function override should not be reported as the interface of class that defines the function might be out of scope of the project
+     * in which case the function name can not be changed. Note that the function will still be reported at the interface or class itself
+     * whenever that interface or class is defined inside the scope of the project.
+     */
+    private fun ASTNode.isOverrideFunction() =
+        findChildByType(MODIFIER_LIST)
+            ?.children()
+            .orEmpty()
+            .any { it.elementType == OVERRIDE_KEYWORD }
+
     private companion object {
         val VALID_FUNCTION_NAME_REGEXP = "[a-z][A-Za-z\\d]*".regExIgnoringDiacriticsAndStrokesOnLetters()
         val VALID_TEST_FUNCTION_NAME_REGEXP = "(`.*`)|([a-z][A-Za-z\\d_]*)".regExIgnoringDiacriticsAndStrokesOnLetters()

ktlint-ruleset-standard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionNamingRuleTest.kt

@@ -182,4 +182,18 @@ class FunctionNamingRuleTest {
             """.trimIndent()
         functionNamingRuleAssertThat(code).hasNoLintViolations()
     }
+
+    @Test
+    fun `Issue 2271 - Given an override fun then do not report a violation of the rule as it might not be possible to change the signature of the rule when defined outside scope of project`() {
+        val code =
+            """
+            // Assume that Bar is defined outside the scope of the project. As of that the function signature can not be changed to comply
+            // to the function-naming rule. In case that Bar is defined inside the scope of the project, the violation will still be
+            // reported in the Bar class/interface itself.
+            class Foo : Bar {
+                override fun Something()
+            }
+            """.trimIndent()
+        functionNamingRuleAssertThat(code).hasNoLintViolations()
+    }
 }