Allow explicit CCN syntax

libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo3/ast/gql.kt

@@ -1529,15 +1529,17 @@ class GQLNullDesignator(override val sourceLocation: SourceLocation? = null) : G
 @ApolloExperimental
 class GQLListNullability(
     override val sourceLocation: SourceLocation? = null,
-    val itemNullability: GQLNullability,
+    val itemNullability: GQLNullability?,
     val selfNullability: GQLNullability?,
 ) : GQLNullability {
   override val children: List<GQLNode>
-    get() = listOf(itemNullability)
+    get() = listOfNotNull(itemNullability)
 
   override fun writeInternal(writer: SDLWriter) {
     writer.write("[")
-    writer.write(itemNullability)
+    if (itemNullability != null) {
+      writer.write(itemNullability)
+    }
     writer.write("]")
     if (selfNullability != null) {
       writer.write(selfNullability)
@@ -1552,7 +1554,7 @@ class GQLListNullability(
 
   fun copy(
       sourceLocation: SourceLocation? = this.sourceLocation,
-      ofNullability: GQLNullability = this.itemNullability,
+      ofNullability: GQLNullability? = this.itemNullability,
       selfNullability: GQLNullability? = this.selfNullability,
   ): GQLListNullability {
     return GQLListNullability(

libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo3/ast/gqltype.kt

@@ -35,15 +35,15 @@ internal fun isVariableUsageAllowed(variableDefinition: GQLVariableDefinition, u
 }
 
 internal fun areTypesCompatible(variableType: GQLType, locationType: GQLType): Boolean {
-  return if(locationType is GQLNonNullType) {
+  return if (locationType is GQLNonNullType) {
     if (variableType !is GQLNonNullType) {
       false
     } else {
       areTypesCompatible(variableType.type, locationType.type)
     }
   } else if (variableType is GQLNonNullType) {
     areTypesCompatible(variableType.type, locationType)
-  } else if (locationType is GQLListType){
+  } else if (locationType is GQLListType) {
     if (variableType !is GQLListType) {
       false
     } else {
@@ -84,43 +84,43 @@ internal fun GQLType.isOutputType(typeDefinitions: Map<String, GQLTypeDefinition
   }
 }
 
-private fun GQLNullability?.selfNullability(): GQLNullability? {
-  return when (this) {
-    is GQLListNullability -> this.selfNullability
-    else -> this
-  }
-}
-
-private fun GQLType.withListNullability(nullability: GQLNullability?): GQLType {
-  if (this is GQLListType && nullability is GQLListNullability) {
-    return copy(type = type.withNullability(nullability.itemNullability))
-  } else if (this is GQLListType && nullability !is GQLListNullability) {
+private fun GQLType.withItemNullability(itemNullability: GQLNullability?): GQLType {
+  if (itemNullability == null) {
     return this
-  } else if (this !is GQLListType && nullability is GQLListNullability) {
-    return this
-  } else if (this !is GQLListType && nullability !is GQLListNullability) {
-    return this
-  } else {
-    error("")
   }
+
+  check(this is GQLListType)
+
+  return this.copy(type = type.withNullability(itemNullability))
 }
 
 @ApolloExperimental
 fun GQLType.withNullability(nullability: GQLNullability?): GQLType {
-  val selfNullability = nullability.selfNullability()
+  val selfNullability: GQLNullability?
+  val itemNullability: GQLNullability?
 
-  if (this is GQLNonNullType && selfNullability == null) {
-    return this.copy(type = type.withListNullability(nullability))
+  when(nullability) {
+    is GQLListNullability -> {
+      selfNullability = nullability.selfNullability
+      itemNullability = nullability.itemNullability
+    }
+    else -> {
+      selfNullability = nullability
+      itemNullability = null
+    }
+  }
+  return if (this is GQLNonNullType && selfNullability == null) {
+    this.copy(type = type.withItemNullability(itemNullability))
   } else if (this is GQLNonNullType && selfNullability is GQLNonNullDesignator) {
-    return this.copy(type = type.withListNullability(nullability))
+    this.copy(type = type.withItemNullability(itemNullability))
   } else if (this is GQLNonNullType && selfNullability is GQLNullDesignator) {
-    return this.type.withListNullability(nullability)
+    this.type.withItemNullability(itemNullability)
   } else if (this !is GQLNonNullType && selfNullability == null) {
-    return this.withListNullability(nullability)
+    this.withItemNullability(itemNullability)
   } else if (this !is GQLNonNullType && selfNullability is GQLNonNullDesignator) {
-    return GQLNonNullType(type = this.withListNullability(nullability))
+    GQLNonNullType(type = this.withItemNullability(itemNullability))
   } else if (this !is GQLNonNullType && selfNullability is GQLNullDesignator) {
-    return this.withListNullability(nullability)
+    this.withItemNullability(itemNullability)
   } else {
     error("")
   }

libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo3/ast/internal/ExecutableValidationScope.kt

@@ -17,14 +17,14 @@ import com.apollographql.apollo3.ast.GQLListType
 import com.apollographql.apollo3.ast.GQLListValue
 import com.apollographql.apollo3.ast.GQLNamedType
 import com.apollographql.apollo3.ast.GQLNode
+import com.apollographql.apollo3.ast.GQLNonNullDesignator
 import com.apollographql.apollo3.ast.GQLNonNullType
+import com.apollographql.apollo3.ast.GQLNullDesignator
 import com.apollographql.apollo3.ast.GQLNullValue
 import com.apollographql.apollo3.ast.GQLNullability
 import com.apollographql.apollo3.ast.GQLObjectTypeDefinition
 import com.apollographql.apollo3.ast.GQLObjectValue
 import com.apollographql.apollo3.ast.GQLOperationDefinition
-import com.apollographql.apollo3.ast.GQLNullDesignator
-import com.apollographql.apollo3.ast.GQLNonNullDesignator
 import com.apollographql.apollo3.ast.GQLScalarTypeDefinition
 import com.apollographql.apollo3.ast.GQLSelection
 import com.apollographql.apollo3.ast.GQLStringValue
@@ -246,7 +246,7 @@ internal class ExecutableValidationScope(
 
   private fun GQLNullability.listDimension(): Int {
     return when (this) {
-      is GQLListNullability -> 1 + this.itemNullability.listDimension()
+      is GQLListNullability -> 1 + (this.itemNullability?.listDimension() ?: 0)
       is GQLNullDesignator -> 0
       is GQLNonNullDesignator -> 0
     }

libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo3/ast/internal/Parser.kt

@@ -265,17 +265,12 @@ internal class Parser(
   }
 
   private fun parseListNullability(): GQLListNullability {
-    val start = token
     val sourceLocation = sourceLocation()
 
     expectToken<Token.LeftBracket>()
     val ofNullability = parseNullability()
     expectToken<Token.RightBracket>()
 
-    if (ofNullability == null) {
-      throw ParserException("List nullability must not be empty", start)
-    }
-
     return GQLListNullability(
         sourceLocation = sourceLocation,
         itemNullability = ofNullability,

tests/ccn/src/main/graphql/operation.graphql

@@ -11,5 +11,8 @@ query GetList {
     enemies[!]! {
       name
     }
+    frenemies: enemies[]! {
+      name
+    }
   }
 }

tests/ccn/src/test/kotlin/test/CcnTest.kt

@@ -40,7 +40,8 @@ class CcnTest {
               {
                 "name": "nullability"
               }
-            ]
+            ],
+            "frenemies": []
           }
         }
       }
@@ -54,5 +55,6 @@ class CcnTest {
     }
     assertEquals(null, response.data!!.user!!.friends[0]?.name)
     assertEquals("nullability", response.data!!.user!!.enemies[0].name)
+    assertEquals(0, response.data!!.user!!.frenemies.size)
   }
 }