Allow factory methods to use generics, and to overload other factory …

…method or class constructor without specifying type Closes #2350
pinterest · Nov 19, 2023 · eaf9eba · eaf9eba
1 parent 7c56501
commit eaf9eba
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diff --git a/...tandard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionNamingRule.kt b/...tandard/src/main/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionNamingRule.kt
@@ -3,12 +3,15 @@ package com.pinterest.ktlint.ruleset.standard.rules
 import com.pinterest.ktlint.rule.engine.core.api.ElementType
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.ANNOTATION
 import com.pinterest.ktlint.rule.engine.core.api.ElementType.ANNOTATION_ENTRY
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.CALL_EXPRESSION
 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.REFERENCE_EXPRESSION
+import com.pinterest.ktlint.rule.engine.core.api.ElementType.USER_TYPE
 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
@@ -81,7 +84,34 @@ public class FunctionNamingRule :
 
     private fun ASTNode.isFactoryMethod() =
         (this.psi as KtFunction)
-            .let { it.hasDeclaredReturnType() && it.name == it.typeReference?.text }
+            .let { ktFunction ->
+                if (ktFunction.hasDeclaredReturnType()) {
+                    // Allow:
+                    //     fun Foo(): Foo = ..
+                    //     fun <T> Foo(action: () -> T): Foo<T> = ..
+                    ktFunction.name == ktFunction.typeReferenceNameWithoutGenerics()
+                } else {
+                    // Allow factory methods to overload another factory method or class constructor without specifying the type like:
+                    //     fun Foo(value: Bar) = Foo(value.baz())
+                    ktFunction.name == callExpressionReferenceIdentifier(ktFunction)
+                }
+            }
+
+    private fun KtFunction.typeReferenceNameWithoutGenerics() =
+        typeReference
+            ?.node
+            ?.findChildByType(USER_TYPE)
+            ?.findChildByType(REFERENCE_EXPRESSION)
+            ?.text
+
+    private fun callExpressionReferenceIdentifier(ktFunction: KtFunction) =
+        ktFunction
+            .bodyExpression
+            ?.node
+            ?.takeIf { it.elementType == CALL_EXPRESSION }
+            ?.findChildByType(REFERENCE_EXPRESSION)
+            ?.findChildByType(IDENTIFIER)
+            ?.text
 
     private fun ASTNode.isMethodInTestClass() = isTestClass && hasValidTestFunctionName()
 

diff --git a/...ard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionNamingRuleTest.kt b/...ard/src/test/kotlin/com/pinterest/ktlint/ruleset/standard/rules/FunctionNamingRuleTest.kt
@@ -237,4 +237,24 @@ class FunctionNamingRuleTest {
             .withEditorConfigOverride(IGNORE_WHEN_ANNOTATED_WITH_PROPERTY to "Composable, Foo")
             .hasNoLintViolations()
     }
+
+    @Test
+    fun `Issue 2350 - Given a factory method with generic type`() {
+        val code =
+            """
+            fun <T> Generics(action: () -> T): Generics<T> = Generics(action())
+            """.trimIndent()
+        functionNamingRuleAssertThat(code).hasNoLintViolations()
+    }
+
+    @Test
+    fun `Issue 2350 - Given a factory method which overloads a class constructor`() {
+        val code =
+            """
+            class Foo(value: String)
+
+            fun Foo(value: Double) = Foo(value.toString())
+            """.trimIndent()
+        functionNamingRuleAssertThat(code).hasNoLintViolations()
+    }
 }