Do not add a space after the typealias name (type-parameter-list-spacing)

CHANGELOG.md

@@ -7,6 +7,7 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ### Added
 
 ### Fixed
+- Do not add a space after the typealias name (`type-parameter-list-spacing`) ([#1435](https://github.com/pinterest/ktlint/issues/1435))
 
 ### Changed
 * Set Kotlin development version to `1.6.21` and Kotlin version to `1.6.21`.

ktlint-ruleset-experimental/src/main/kotlin/com/pinterest/ktlint/ruleset/experimental/TypeParameterListSpacingRule.kt

@@ -4,9 +4,12 @@ import com.pinterest.ktlint.core.Rule
 import com.pinterest.ktlint.core.ast.ElementType.CLASS
 import com.pinterest.ktlint.core.ast.ElementType.CLASS_BODY
 import com.pinterest.ktlint.core.ast.ElementType.CONSTRUCTOR_KEYWORD
+import com.pinterest.ktlint.core.ast.ElementType.EQ
+import com.pinterest.ktlint.core.ast.ElementType.FUN
 import com.pinterest.ktlint.core.ast.ElementType.GT
 import com.pinterest.ktlint.core.ast.ElementType.LT
 import com.pinterest.ktlint.core.ast.ElementType.PRIMARY_CONSTRUCTOR
+import com.pinterest.ktlint.core.ast.ElementType.TYPEALIAS
 import com.pinterest.ktlint.core.ast.ElementType.TYPE_PARAMETER_LIST
 import com.pinterest.ktlint.core.ast.ElementType.WHITE_SPACE
 import com.pinterest.ktlint.core.ast.nextCodeSibling
@@ -31,10 +34,10 @@ public class TypeParameterListSpacingRule : Rule("type-parameter-list-spacing")
             return
         }
 
-        if (node.treeParent.elementType == CLASS) {
-            visitClassDeclaration(node, autoCorrect, emit)
-        } else {
-            visitFunctionDeclaration(node, autoCorrect, emit)
+        when (node.treeParent.elementType) {
+            CLASS -> visitClassDeclaration(node, autoCorrect, emit)
+            TYPEALIAS -> visitTypeAliasDeclaration(node, autoCorrect, emit)
+            FUN -> visitFunctionDeclaration(node, autoCorrect, emit)
         }
         visitInsideTypeParameterList(node, autoCorrect, emit)
     }
@@ -77,6 +80,26 @@ public class TypeParameterListSpacingRule : Rule("type-parameter-list-spacing")
             ?.let { singleSpaceExpected(it, autoCorrect, emit) }
     }
 
+    private fun visitTypeAliasDeclaration(
+        node: ASTNode,
+        autoCorrect: Boolean,
+        emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit
+    ) {
+        // No white space expected between typealias keyword name and parameter list
+        //     typealias Bar <T>
+        node
+            .prevSibling { true }
+            ?.takeIf { it.elementType == WHITE_SPACE }
+            ?.let { noWhitespaceExpected(it, autoCorrect, emit) }
+
+        // No white space expected between parameter type list and equals sign
+        //    typealias Bar<T> = ...
+        node
+            .nextSibling { true }
+            ?.takeIf { it.elementType == WHITE_SPACE && it.nextCodeSibling()?.elementType == EQ }
+            ?.let { singleSpaceExpected(it, autoCorrect, emit) }
+    }
+
     private fun visitFunctionDeclaration(
         node: ASTNode,
         autoCorrect: Boolean,

ktlint-ruleset-experimental/src/test/kotlin/com/pinterest/ktlint/ruleset/experimental/TypeParameterListSpacingRuleTest.kt

@@ -307,4 +307,21 @@ class TypeParameterListSpacingRuleTest {
         )
         assertThat(TypeParameterListSpacingRule().format(code)).isEqualTo(formattedCode)
     }
+
+    @Test
+    fun `Given a typealias definition with a type parameter list followed by a parameter list then the redundant spaces are removed`() {
+        val code =
+            """
+            typealias Bar  <T>  = () -> T
+            """.trimIndent()
+        val formattedCode =
+            """
+            typealias Bar<T> = () -> T
+            """.trimIndent()
+        assertThat(TypeParameterListSpacingRule().lint(code)).containsExactly(
+            LintError(1, 14, "type-parameter-list-spacing", "No whitespace expected at this position"),
+            LintError(1, 19, "type-parameter-list-spacing", "Expected a single space")
+        )
+        assertThat(TypeParameterListSpacingRule().format(code)).isEqualTo(formattedCode)
+    }
 }