Use required on input, nullable on output to determine GraphQL nullability

packages/openapi-to-graphql/src/oas_3_tools.ts

@@ -389,6 +389,25 @@ export function resolveAllOf<TSource, TContext, TArgs>(
           }
         })
       }
+
+      // Collapse nullable if applicable
+      if (typeof collapsedMemberSchema.nullable !== 'undefined') {
+        if (typeof collapsedSchema.nullable === 'undefined') {
+          collapsedSchema.nullable = collapsedMemberSchema.nullable
+
+          // Check for incompatible nullable property
+        } else if (collapsedSchema.nullable !== collapsedMemberSchema.nullable) {
+          handleWarning({
+            mitigationType: MitigationTypes.UNRESOLVABLE_SCHEMA,
+            message:
+              `Resolving 'allOf' field in schema '${JSON.stringify(
+                collapsedSchema
+              )}' ` + `results in incompatible nullable property.`,
+            data,
+            log: preprocessingLog
+          })
+        }
+      }
     })
   }
 

packages/openapi-to-graphql/src/preprocessor.ts

@@ -696,6 +696,7 @@ export function createDataDef<TSource, TContext, TArgs>(
       preferredName,
       schema: null,
       required: [],
+      nullable: null,
       links: null,
       subDefinitions: null,
       graphQLTypeName: null,
@@ -794,6 +795,7 @@ export function createDataDef<TSource, TContext, TArgs>(
      */
     schema,
     required: [],
+    nullable: collapsedSchema.nullable,
     targetGraphQLType, // May change due to allOf and oneOf resolution
     subDefinitions: undefined,
     links: saneLinks,

packages/openapi-to-graphql/src/schema_builder.ts

@@ -662,10 +662,34 @@ function createFields<TSource, TContext, TArgs extends object>({
       iteration: iteration + 1,
       isInputObjectType,
       fetch
-    })
+    }) as GraphQLObjectType | GraphQLInputObjectType
+
+
+    /* On requiredness / nullability
+
+      In GraphQL, fields are either wrapped in a `GraphQLNonNull` (type ends with `!`) or not.
+      In input types, a field with `GraphQLNonNull` type [must be present and must not be `null`](https://spec.graphql.org/October2021/#sec-Non-Null.Input-Coercion)
+      In output types, a field with `GraphQLNonNull` type [cannot return a `null` value](https://spec.graphql.org/October2021/#sec-Value-Completion)
+
+      The OpenAPI spec is [not clear on the meaning of "required"](https://swagger.io/docs/specification/data-models/data-types/#required)
+      but the JSON schema specification that OpenAPI 3.0 uses [is clearer](https://json-schema.org/specification-links#draft-5)
+        > An object instance is valid against this keyword if its property set contains all elements in this keyword's array value.
+      Essentially, we can interpret "required" as "must be present in the object."
+
+      The OpenAPI spec also [provides a "nullable" property](https://swagger.io/docs/specification/data-models/data-types/#null)
+        > [nullable: true will] specify that the value may be null
+      Essentially, we can interpret "nullable" as "may be `null` (if present)."
+
+      In OpenAPI, the same component schema can be used as both input and output types. So we must interpret "required" and "nullable" differently.
+      For input types, we must interpret "required" as `GraphQLNonNull` and ignore "nullable" (since `GraphQLNonNull` implies non-nullable).
+      For output types, we must interpret "nullable" as `GraphQLNonNull` and ignore "required" (since presence in output is determined by the query).
+    */
+
+    // If the data is not present, assume nullable (GraphQL fields are null by default)
 
-    const requiredProperty =
-      typeof def.required === 'object' && def.required.includes(fieldName)
+    const nonNullProperty = isInputObjectType ?
+      def.schema.required?.includes(fieldName) :
+      fieldTypeDefinition.nullable === false
 
     // Finally, add the object type to the fields (using sanitized field name)
     if (objectType) {
@@ -706,7 +730,7 @@ function createFields<TSource, TContext, TArgs extends object>({
       )
 
       fields[sanePropName] = {
-        type: requiredProperty
+        type: nonNullProperty
           ? new GraphQLNonNull(objectType as GraphQLOutputType)
           : (objectType as GraphQLOutputType),
 

packages/openapi-to-graphql/src/types/operation.ts

@@ -68,6 +68,13 @@ export type DataDefinition = {
    */
   required: string[]
 
+  /**
+   * Similar to the nullable property in object schemas but because of certain
+   * keywords to combine schemas, e.g. "allOf", this resolves the nullable
+   * property in all member schemas
+   */
+  nullable?: boolean
+
   // The type GraphQL type this dataDefintion will be created into
   targetGraphQLType: TargetGraphQLType
 

packages/openapi-to-graphql/test/example_api.test.ts

@@ -431,7 +431,7 @@ test('Link parameters as constants and variables', () => {
           },
           everythingLink: {
             body:
-              'http://localhost:3002/api/scanner_get_200_hello_application/json_close'
+              'http://localhost:3002/api/scanner_get_200_hello_application/json_16'
           }
         }
       }
@@ -493,10 +493,10 @@ test('Nested links with constants and variables', () => {
               body: '123',
               everythingLink: {
                 body:
-                  'http://localhost:3002/api/copier_get_200_123_application/json_close',
+                  'http://localhost:3002/api/copier_get_200_123_application/json_14',
                 everythingLink: {
                   body:
-                    'http://localhost:3002/api/copier_get_200_http://localhost:3002/api/copier_get_200_123_application/json_close_application/json_close'
+                    'http://localhost:3002/api/copier_get_200_http://localhost:3002/api/copier_get_200_123_application/json_14_application/json_75'
                 }
               }
             }
@@ -506,7 +506,7 @@ test('Nested links with constants and variables', () => {
           },
           everythingLink: {
             body:
-              'http://localhost:3002/api/scanner_get_200_val_application/json_close'
+              'http://localhost:3002/api/scanner_get_200_val_application/json_14'
           }
         }
       }
@@ -531,7 +531,7 @@ test('Link parameters as constants and variables with request payload', () => {
           body: 'req.body: body, req.query.query: query, req.path.path: path',
           everythingLink2: {
             body:
-              'http://localhost:3002/api/scanner/path_post_200_body_query_path_application/json_req.body: body, req.query.query: query, req.path.path: path_query_path_close'
+              'http://localhost:3002/api/scanner/path_post_200_body_query_path_application/json_req.body: body, req.query.query: query, req.path.path: path_query_path_70'
           }
         }
       }
@@ -642,8 +642,8 @@ test('Get response containing 64-bit integer (using GraphQLBigInt)', () => {
     expect(result).toEqual({
       data: {
         productReviews: [
-          { timestamp: BigInt('1502787600000000') },
-          { timestamp: BigInt('1502787400000000') }
+          { timestamp: Number('1502787600000000') },
+          { timestamp: Number('1502787400000000') }
         ]
       }
     })

packages/openapi-to-graphql/test/file_upload.test.ts

@@ -119,6 +119,9 @@ test('Upload completes without any error', async () => {
   const graphqlServer = createServer(async (req, res) => {
     try {
       const operation = await processRequest(req, res)
+      if (Array.isArray(operation)) {
+        throw new Error('Expected a single operation')
+      }
       const result = await graphql({ schema: createdSchema, source: operation.query, variableValues: operation.variables as GraphQLArgs['variableValues'] })
       res.end(JSON.stringify(result))
     } catch (e) {

packages/openapi-to-graphql/test/fixtures/example_oas.json

@@ -1316,13 +1316,14 @@
       },
       "coordinates": {
         "type": "object",
-        "required": ["lat", "long"],
         "properties": {
           "lat": {
-            "type": "number"
+            "type": "number",
+            "nullable": false
           },
           "long": {
-            "type": "number"
+            "type": "number",
+            "nullable": false
           }
         }
       },
@@ -1332,10 +1333,16 @@
           {
             "properties": {
               "family": {
-                "$ref": "#/components/schemas/familyString"
+                "allOf": [
+                  {
+                    "$ref": "#/components/schemas/familyString"
+                  },
+                  {
+                    "nullable": false
+                  }
+                ]
               }
-            },
-            "required": ["family"]
+            }
           },
           {
             "properties": {
@@ -1388,7 +1395,8 @@
           "patent-id": {
             "type": "string",
             "description": "The id of the patent",
-            "format": "specialIdFormat"
+            "format": "specialIdFormat",
+            "nullable": false
           },
           "inventor-id": {
             "type": "string",
@@ -1600,13 +1608,13 @@
       "EverythingLink": {
         "operationId": "getCopier",
         "parameters": {
-          "query": "{$url}_{$method}_{$statusCode}_{$request.query.query}_{$request.header.accept}_{$response.header.connection}"
+          "query": "{$url}_{$method}_{$statusCode}_{$request.query.query}_{$request.header.accept}_{$response.header.content-length}"
         }
       },
       "EverythingLink2": {
         "operationId": "getCopier",
         "parameters": {
-          "query": "{$url}_{$method}_{$statusCode}_{$request.body}_{$request.query.query}_{$request.path.path}_{$request.header.accept}_{$response.body#/body}_{$response.query.query}_{$response.path.path}_{$response.header.connection}"
+          "query": "{$url}_{$method}_{$statusCode}_{$request.body}_{$request.query.query}_{$request.path.path}_{$request.header.accept}_{$response.body#/body}_{$response.query.query}_{$response.path.path}_{$response.header.content-length}"
         }
       },
       "Reviews": {

packages/openapi-to-graphql/test/fixtures/example_oas6.json

@@ -436,7 +436,7 @@
             "type": "number"
           },
           "previous_owner": {
-            "description": "Previouw owner of the pet",
+            "description": "Previous owner of the pet",
             "type": "string"
           },
           "history": {
@@ -446,7 +446,8 @@
               "data": {
                 "type": "string"
               }
-            }
+            },
+            "nullable": false
           },
           "history2": {
             "description": "History of the pet",