omit more permissive modifiers on restricted visibility types

docs/changelog.md

@@ -20,6 +20,7 @@ Change Log
 * Fix: Throw if primary constructor delegates to other constructors (#1859).
 * Fix: Aliased imports with nested class (#1876).
 * Fix: Check for error types in `KSType.toClassName()` (#1890).
+* Fix: Omit more permissive modifiers on restricted visibility types (#1301).
 
 ## Version 1.16.0
 

kotlinpoet/src/commonMain/kotlin/com/squareup/kotlinpoet/CodeWriter.kt

@@ -161,11 +161,19 @@ internal class CodeWriter constructor(
       emit(KModifier.PUBLIC.keyword)
       emit(" ")
     }
+
+    // public always being an implicit modifier in addition to whatever we inherited.
+    // we don't want to throw away the implicit modifier we inherited
+    val implicitModifierContainsAtLeastTwoAccessModifiers = implicitModifiers.count {
+      it == KModifier.PUBLIC || it == KModifier.PRIVATE || it == KModifier.INTERNAL || it == KModifier.PROTECTED
+    } >= 2
+
     val uniqueNonPublicExplicitOnlyModifiers =
       modifiers
         .filterNot { it == KModifier.PUBLIC }
-        .filterNot { implicitModifiers.contains(it) }
+        .filterNot { implicitModifiers.contains(it) && implicitModifierContainsAtLeastTwoAccessModifiers.not() }
         .toEnumSet()
+
     for (modifier in uniqueNonPublicExplicitOnlyModifiers) {
       emit(modifier.keyword)
       emit(" ")
@@ -652,6 +660,11 @@ internal class CodeWriter constructor(
       return false
     }
 
+    if (implicitModifiers.containsAnyOf(KModifier.INTERNAL, KModifier.PRIVATE, KModifier.PROTECTED)) {
+      // omit more permissive modifiers on more restrictive visibility modifiers
+      return false
+    }
+
     if (!implicitModifiers.contains(KModifier.PUBLIC)) {
       return false
     }

kotlinpoet/src/commonMain/kotlin/com/squareup/kotlinpoet/TypeSpec.kt

@@ -171,7 +171,7 @@ public class TypeSpec private constructor(
         codeWriter.emitAnnotations(annotations, false)
         codeWriter.emitModifiers(
           modifiers,
-          if (isNestedExternal) setOf(PUBLIC, EXTERNAL) else setOf(PUBLIC),
+          implicitModifiers + if (isNestedExternal) setOf(PUBLIC, EXTERNAL) else setOf(PUBLIC),
         )
         codeWriter.emit(kind.declarationKeyword)
         if (name != null) {
@@ -446,6 +446,9 @@ public class TypeSpec private constructor(
         ANNOTATION in modifiers -> emptySet()
         EXPECT in modifiers -> setOf(EXPECT)
         EXTERNAL in modifiers -> setOf(EXTERNAL)
+        INTERNAL in modifiers -> setOf(INTERNAL)
+        PRIVATE in modifiers -> setOf(PRIVATE)
+        PROTECTED in modifiers -> setOf(PROTECTED)
         else -> emptySet()
       }
     }
@@ -454,6 +457,9 @@ public class TypeSpec private constructor(
       return defaultImplicitFunctionModifiers + when {
         EXPECT in modifiers -> setOf(EXPECT)
         EXTERNAL in modifiers -> setOf(EXTERNAL)
+        INTERNAL in modifiers -> setOf(INTERNAL)
+        PRIVATE in modifiers -> setOf(PRIVATE)
+        PROTECTED in modifiers -> setOf(PROTECTED)
         else -> emptySet()
       }
     }
@@ -462,6 +468,9 @@ public class TypeSpec private constructor(
       return defaultImplicitTypeModifiers + when {
         EXPECT in modifiers -> setOf(EXPECT)
         EXTERNAL in modifiers -> setOf(EXTERNAL)
+        INTERNAL in modifiers -> setOf(INTERNAL)
+        PRIVATE in modifiers -> setOf(PRIVATE)
+        PROTECTED in modifiers -> setOf(PROTECTED)
         else -> emptySet()
       }
     }