feat: allow nullable return and voidable params (#331)

closes #278

packages/graphqlgen/src/generators/common.spec.ts

@@ -41,6 +41,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
         {
@@ -56,6 +57,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
@@ -85,6 +87,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
@@ -114,6 +117,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],
@@ -143,6 +147,7 @@ it('getDistinctInputTypes', () => {
             isUnion: false,
             isRequired: false,
             isArray: false,
+            isArrayRequired: false,
           },
         },
       ],

packages/graphqlgen/src/generators/common.ts

@@ -188,29 +188,88 @@ export function shouldScaffoldFieldResolver(
   return !shouldRenderDefaultResolver(graphQLField, modelField, args)
 }
 
-export function printFieldLikeType(
+const nullable = (type: string): string => {
+  return `${type} | null`
+}
+
+const kv = (
+  key: string,
+  value: string,
+  isOptional: boolean = false,
+): string => {
+  return `${key}${isOptional ? '?' : ''}: ${value}`
+}
+
+const array = (innerType: string, config: { innerUnion?: boolean } = {}) => {
+  return config.innerUnion ? `${innerType}[]` : `Array<${innerType}>`
+}
+
+type FieldPrintOptions = {
+  isReturn?: boolean
+}
+
+export const printFieldLikeType = (
   field: GraphQLTypeField,
   modelMap: ModelMap,
-) {
-  const isNullable =
-    field.defaultValue === null ||
-    (!field.type.isRequired && field.defaultValue === undefined)
-
-  if (field.type.isScalar) {
-    return `${getTypeFromGraphQLType(field.type.name)}${
-      field.type.isArray ? '[]' : ''
-    }${isNullable ? '| null' : ''}`
+  options: FieldPrintOptions = {
+    isReturn: false,
+  },
+): string => {
+  const name = field.type.isScalar
+    ? getTypeFromGraphQLType(field.type.name)
+    : field.type.isInput || field.type.isEnum
+    ? field.type.name
+    : getModelName(field.type, modelMap)
+
+  /**
+   * Considerable difference between types in array versus not, such as what
+   * default value means, isRequired, ..., lead to forking the rendering paths.
+   *
+   * Regarding voidable, note how it can only show up in the k:v rendering e.g.:
+   *
+   *     foo?: null | string
+   *
+   * but not for return style e.g.:
+   *
+   *     undefined | null | string
+   *
+   * given footnote 1 below.
+   *
+   * 1. Return type doesn't permit void return since that would allow
+   *    resolvers to e.g. forget to return anything and that be considered OK.
+   */
+
+  if (field.type.isArray) {
+    const innerUnion = field.type.isRequired
+
+    // - Not voidable here because a void array member is not possible
+    // - For arrays default value does not apply to inner value
+    const valueInnerType = field.type.isRequired ? name : nullable(name)
+
+    const isArrayNullable =
+      !field.type.isArrayRequired &&
+      (field.defaultValue === undefined || field.defaultValue === null)
+
+    const isArrayVoidable = isArrayNullable && field.defaultValue === undefined
+
+    const valueType = isArrayNullable
+      ? nullable(array(valueInnerType, { innerUnion })) // [1]
+      : array(valueInnerType, { innerUnion })
+
+    return options.isReturn
+      ? valueType
+      : kv(field.name, valueType, isArrayVoidable)
+  } else {
+    const isNullable =
+      !field.type.isRequired &&
+      (field.defaultValue === undefined || field.defaultValue === null)
+
+    const isVoidable = isNullable && field.defaultValue === undefined
+
+    const valueType = isNullable ? nullable(name) : name // [1]
+
+    return options.isReturn ? valueType : kv(field.name, valueType, isVoidable)
   }
-
-  if (field.type.isInput || field.type.isEnum) {
-    return `${field.type.name}${field.type.isArray ? '[]' : ''}${
-      isNullable ? '| null' : ''
-    }`
-  }
-
-  return `${getModelName(field.type, modelMap)}${
-    field.type.isArray ? '[]' : ''
-  }${isNullable ? '| null' : ''}`
 }
 
 export function getTypeFromGraphQLType(

packages/graphqlgen/src/generators/flow-generator.ts

@@ -170,8 +170,8 @@ function renderInputTypeInterfaces(
       return `export interface ${upperFirst(type.name)}_${upperFirst(
         inputTypesMap[typeAssociation].name,
       )} {
-      ${inputTypesMap[typeAssociation].fields.map(
-        field => `${field.name}: ${printFieldLikeType(field, modelMap)}`,
+      ${inputTypesMap[typeAssociation].fields.map(field =>
+        printFieldLikeType(field, modelMap),
       )}
     }`
     })
@@ -199,12 +199,11 @@ function renderInputArgInterface(
   return `
   export interface ${getInputArgName(type, field)} {
     ${field.arguments
-      .map(
-        arg =>
-          `${arg.name}: ${getArgTypePrefix(type, arg)}${printFieldLikeType(
-            arg as GraphQLTypeField,
-            modelMap,
-          )}`,
+      .map(arg =>
+        printFieldLikeType(arg as GraphQLTypeField, modelMap).replace(
+          ': ',
+          `: ${getArgTypePrefix(type, arg)}`,
+        ),
       )
       .join(',' + os.EOL)}
   }
@@ -254,7 +253,10 @@ function renderResolverFunctionInterface(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeType(field, modelMap)
+
+  const returnType = printFieldLikeType(field, modelMap, {
+    isReturn: true,
+  })
 
   if (type.name === 'Subscription') {
     return `
@@ -299,7 +301,9 @@ function renderResolverTypeInterfaceFunction(
     ctx: ${getContextName(context)},
     info: GraphQLResolveInfo,
   )`
-  const returnType = printFieldLikeType(field, modelMap)
+  const returnType = printFieldLikeType(field, modelMap, {
+    isReturn: true,
+  })
 
   if (type.name === 'Subscription') {
     return `

packages/graphqlgen/src/generators/ts-generator.ts

@@ -194,8 +194,8 @@ function renderInputTypeInterfaces(
   return getDistinctInputTypes(type, typeToInputTypeAssociation, inputTypesMap)
     .map(typeAssociation => {
       return `export interface ${inputTypesMap[typeAssociation].name} {
-      ${inputTypesMap[typeAssociation].fields.map(
-        field => `${field.name}: ${printFieldLikeType(field, modelMap)}`,
+      ${inputTypesMap[typeAssociation].fields.map(field =>
+        printFieldLikeType(field, modelMap),
       )}
     }`
     })
@@ -222,13 +222,7 @@ function renderInputArgInterface(
   return `
   export interface Args${upperFirst(field.name)} {
     ${field.arguments
-      .map(
-        arg =>
-          `${arg.name}: ${printFieldLikeType(
-            arg as GraphQLTypeField,
-            modelMap,
-          )}`,
-      )
+      .map(arg => printFieldLikeType(arg as GraphQLTypeField, modelMap))
       .join(os.EOL)}
   }
   `
@@ -263,7 +257,8 @@ function renderResolverFunctionInterface(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeType(field, modelMap)
+
+  const returnType = printFieldLikeType(field, modelMap, { isReturn: true })
 
   if (type.name === 'Subscription') {
     return `
@@ -311,7 +306,7 @@ function renderResolverTypeInterfaceFunction(
     info: GraphQLResolveInfo,
   )
   `
-  const returnType = printFieldLikeType(field, modelMap)
+  const returnType = printFieldLikeType(field, modelMap, { isReturn: true })
 
   if (type.name === 'Subscription') {
     return `

packages/graphqlgen/src/source-helper.ts

@@ -46,6 +46,7 @@ type GraphQLTypeDefinition = {
 
 export type GraphQLType = GraphQLTypeDefinition & {
   isArray: boolean
+  isArrayRequired: boolean
   isRequired: boolean
 }
 
@@ -83,6 +84,7 @@ export type GraphQLUnionObject = {
 interface FinalType {
   isRequired: boolean
   isArray: boolean
+  isArrayRequired: boolean
   type: GraphQLInputType | GraphQLOutputType
 }
 
@@ -130,13 +132,20 @@ function extractTypeDefinition(
 
 const getFinalType = (
   type: GraphQLInputType | GraphQLOutputType,
-  acc: FinalType = { isArray: false, isRequired: false, type },
+  acc: FinalType = {
+    isArray: false,
+    isArrayRequired: false,
+    isRequired: false,
+    type,
+  },
 ): FinalType => {
   if (type instanceof GraphQLNonNull) {
     acc.isRequired = true
   }
   if (type instanceof GraphQLList) {
     acc.isArray = true
+    acc.isArrayRequired = acc.isRequired
+    acc.isRequired = false
   }
 
   if (type instanceof GraphQLNonNull || type instanceof GraphQLList) {
@@ -157,13 +166,21 @@ function extractTypeLike(
   type: GraphQLInputType | GraphQLOutputType,
 ): GraphQLType {
   const typeLike: GraphQLType = {} as GraphQLType
-  const { isArray, isRequired, type: finalType } = getFinalType(type)
+  const {
+    isArray,
+    isArrayRequired,
+    isRequired,
+    type: finalType,
+  } = getFinalType(type)
   if (isRequired) {
     typeLike.isRequired = true
   }
   if (isArray) {
     typeLike.isArray = true
   }
+  if (isArrayRequired) {
+    typeLike.isArrayRequired = true
+  }
   if (
     finalType instanceof GraphQLObjectType ||
     finalType instanceof GraphQLInterfaceType ||