Add require-nullable-result-in-root lint rule

.changeset/dull-tables-mix.md

@@ -0,0 +1,5 @@
+---
+'@graphql-eslint/eslint-plugin': minor
+---
+
+Add `require-nullable-result-in-root` rule to report on non-null fields in root types

packages/plugin/src/configs/schema-all.ts

@@ -18,6 +18,7 @@ export default {
     '@graphql-eslint/require-deprecation-date': 'error',
     '@graphql-eslint/require-field-of-type-query-in-mutation-result': 'error',
     '@graphql-eslint/require-nullable-fields-with-oneof': 'error',
+    '@graphql-eslint/require-nullable-result-in-root': 'error',
     '@graphql-eslint/require-type-pattern-with-oneof': 'error',
   },
 };

packages/plugin/src/rules/index.ts

@@ -31,6 +31,7 @@ import { rule as requireFieldOfTypeQueryInMutationResult } from './require-field
 import { rule as requireIdWhenAvailable } from './require-id-when-available.js';
 import { rule as requireImportFragment } from './require-import-fragment.js';
 import { rule as requireNullableFieldsWithOneof } from './require-nullable-fields-with-oneof.js';
+import { rule as requireNullableResultInRoot } from './require-nullable-result-in-root.js';
 import { rule as requireTypePatternWithOneof } from './require-type-pattern-with-oneof.js';
 import { rule as selectionSetDepth } from './selection-set-depth.js';
 import { rule as strictIdInTypes } from './strict-id-in-types.js';
@@ -67,6 +68,7 @@ export const rules = {
   'require-id-when-available': requireIdWhenAvailable,
   'require-import-fragment': requireImportFragment,
   'require-nullable-fields-with-oneof': requireNullableFieldsWithOneof,
+  'require-nullable-result-in-root': requireNullableResultInRoot,
   'require-type-pattern-with-oneof': requireTypePatternWithOneof,
   'selection-set-depth': selectionSetDepth,
   'strict-id-in-types': strictIdInTypes,

packages/plugin/src/rules/require-nullable-result-in-root.ts

@@ -0,0 +1,90 @@
+import { Kind, ObjectTypeDefinitionNode } from 'graphql';
+import { GraphQLESLintRule } from '../types.js';
+import { getNodeName, requireGraphQLSchemaFromContext, truthy } from '../utils.js';
+import { GraphQLESTreeNode } from '../estree-converter/index.js';
+
+const RULE_ID = 'require-nullable-result-in-root';
+
+export const rule: GraphQLESLintRule = {
+  meta: {
+    type: 'suggestion',
+    hasSuggestions: true,
+    docs: {
+      category: 'Schema',
+      description: 'Require nullable fields in root types.',
+      url: `https://github.com/B2o5T/graphql-eslint/blob/master/docs/rules/${RULE_ID}.md`,
+      requiresSchema: true,
+      examples: [
+        {
+          title: 'Incorrect',
+          code: /* GraphQL */ `
+            type Query {
+              user: User!
+            }
+          `,
+        },
+        {
+          title: 'Correct',
+          code: /* GraphQL */ `
+            type Query {
+              foo: User
+              baz: [User]!
+              bar: [User!]!
+            }
+          `,
+        },
+      ],
+    },
+    messages: {
+      [RULE_ID]: 'Unexpected non-null result {{ resultType }} in {{ rootType }}',
+    },
+    schema: [],
+  },
+  create(context) {
+    const schema = requireGraphQLSchemaFromContext(RULE_ID, context);
+    const rootTypeNames = new Set(
+      [schema.getQueryType(), schema.getMutationType(), schema.getSubscriptionType()]
+        .filter(truthy)
+        .map(type => type.name),
+    );
+    const sourceCode = context.getSourceCode();
+
+    return {
+      'ObjectTypeDefinition,ObjectTypeExtension'(
+        node: GraphQLESTreeNode<ObjectTypeDefinitionNode>,
+      ) {
+        if (!rootTypeNames.has(node.name.value)) return;
+
+        for (const field of node.fields || []) {
+          if (
+            field.gqlType.type !== Kind.NON_NULL_TYPE ||
+            field.gqlType.gqlType.type !== Kind.NAMED_TYPE
+          )
+            continue;
+          const name = field.gqlType.gqlType.name.value;
+          const type = schema.getType(name);
+          const resultType = type ? getNodeName(type.astNode as any) : '';
+
+          context.report({
+            node: field.gqlType,
+            messageId: RULE_ID,
+            data: {
+              resultType,
+              rootType: getNodeName(node),
+            },
+            suggest: [
+              {
+                desc: `Make ${resultType} nullable`,
+                fix(fixer) {
+                  const text = sourceCode.getText(field.gqlType as any);
+
+                  return fixer.replaceText(field.gqlType as any, text.replace('!', ''));
+                },
+              },
+            ],
+          });
+        }
+      },
+    };
+  },
+};

packages/plugin/src/utils.ts

@@ -154,6 +154,7 @@ export function displayNodeName(node: GraphQLESTreeNode<ASTNode>): string {
 export function getNodeName(node: GraphQLESTreeNode<ASTNode>): string {
   switch (node.kind) {
     case Kind.OBJECT_TYPE_DEFINITION:
+    case Kind.OBJECT_TYPE_EXTENSION:
     case Kind.INTERFACE_TYPE_DEFINITION:
     case Kind.ENUM_TYPE_DEFINITION:
     case Kind.SCALAR_TYPE_DEFINITION:

packages/plugin/tests/__snapshots__/require-nullable-result-in-root.spec.md

@@ -0,0 +1,63 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`Invalid #1 1`] = `
+#### ⌨️ Code
+
+      1 |         type Query {
+      2 |           user: User!
+      3 |         }
+      4 |         type User {
+      5 |           id: ID!
+      6 |         }
+
+#### ❌ Error
+
+      1 |         type Query {
+    > 2 |           user: User!
+        |                 ^^^^ Unexpected non-null result type "User" in type "Query"
+      3 |         }
+
+#### 💡 Suggestion: Make type "User" nullable
+
+    1 |         type Query {
+    2 |           user: User
+    3 |         }
+    4 |         type User {
+    5 |           id: ID!
+    6 |         }
+`;
+
+exports[`should work with extend query 1`] = `
+#### ⌨️ Code
+
+       1 |         type MyMutation
+       2 |         extend type MyMutation {
+       3 |           user: User!
+       4 |         }
+       5 |         interface User {
+       6 |           id: ID!
+       7 |         }
+       8 |         schema {
+       9 |           mutation: MyMutation
+      10 |         }
+
+#### ❌ Error
+
+      2 |         extend type MyMutation {
+    > 3 |           user: User!
+        |                 ^^^^ Unexpected non-null result interface "User" in type "MyMutation"
+      4 |         }
+
+#### 💡 Suggestion: Make interface "User" nullable
+
+     1 |         type MyMutation
+     2 |         extend type MyMutation {
+     3 |           user: User
+     4 |         }
+     5 |         interface User {
+     6 |           id: ID!
+     7 |         }
+     8 |         schema {
+     9 |           mutation: MyMutation
+    10 |         }
+`;

packages/plugin/tests/require-nullable-result-in-root.spec.ts

@@ -0,0 +1,57 @@
+import { GraphQLRuleTester, ParserOptions } from '../src';
+import { rule } from '../src/rules/require-nullable-result-in-root';
+
+const ruleTester = new GraphQLRuleTester();
+
+function useSchema(code: string): { code: string; parserOptions: Omit<ParserOptions, 'filePath'> } {
+  return {
+    code,
+    parserOptions: { schema: code },
+  };
+}
+
+ruleTester.runGraphQLTests('require-nullable-result-in-root', rule, {
+  valid: [
+    {
+      ...useSchema(/* GraphQL */ `
+        type Query {
+          foo: User
+          baz: [User]!
+          bar: [User!]!
+        }
+        type User {
+          id: ID!
+        }
+      `),
+    },
+  ],
+  invalid: [
+    {
+      ...useSchema(/* GraphQL */ `
+        type Query {
+          user: User!
+        }
+        type User {
+          id: ID!
+        }
+      `),
+      errors: 1,
+    },
+    {
+      name: 'should work with extend query',
+      ...useSchema(/* GraphQL */ `
+        type MyMutation
+        extend type MyMutation {
+          user: User!
+        }
+        interface User {
+          id: ID!
+        }
+        schema {
+          mutation: MyMutation
+        }
+      `),
+      errors: 1,
+    },
+  ],
+});

website/src/pages/rules/_meta.json

@@ -31,6 +31,7 @@
   "require-description": "",
   "require-field-of-type-query-in-mutation-result": "",
   "require-nullable-fields-with-oneof": "",
+  "require-nullable-result-in-root": "",
   "require-type-pattern-with-oneof": "",
   "strict-id-in-types": "",
   "unique-directive-names": "",

website/src/pages/rules/index.md

@@ -59,6 +59,7 @@ Each rule has emojis denoting:
 | [require-id-when-available](/rules/require-id-when-available)                                                                | Enforce selecting specific fields when they are available on the GraphQL type.                                                                                                                          |                    ![recommended][]                    |        📦         |        🚀         |        💡         |
 | [require-import-fragment](/rules/require-import-fragment)                                                                    | Require fragments to be imported via an import expression.                                                                                                                                              |                                                        |        📦         |        🚀         |        💡         |
 | [require-nullable-fields-with-oneof](/rules/require-nullable-fields-with-oneof)                                              | Require `input` or `type` fields to be non-nullable with `@oneOf` directive.                                                                                                                            |                        ![all][]                        |        📄         |        🚀         |
+| [require-nullable-result-in-root](/rules/require-nullable-result-in-root)                                                    | Require nullable fields in root types.                                                                                                                                                                  |                        ![all][]                        |        📄         |        🚀         |        💡         |
 | [require-type-pattern-with-oneof](/rules/require-type-pattern-with-oneof)                                                    | Enforce types with `@oneOf` directive have `error` and `ok` fields.                                                                                                                                     |                        ![all][]                        |        📄         |        🚀         |
 | [scalar-leafs](/rules/scalar-leafs)                                                                                          | A GraphQL document is valid only if all leaf fields (fields without sub selections) are of scalar or enum types.                                                                                        |                    ![recommended][]                    |        📦         |        🔮         |        💡         |
 | [selection-set-depth](/rules/selection-set-depth)                                                                            | Limit the complexity of the GraphQL operations solely by their depth. Based on [graphql-depth-limit](https://npmjs.com/package/graphql-depth-limit).                                                    |                    ![recommended][]                    |        📦         |        🚀         |        💡         |

website/src/pages/rules/require-nullable-result-in-root.md

@@ -0,0 +1,42 @@
+# `require-nullable-result-in-root`
+
+💡 This rule provides
+[suggestions](https://eslint.org/docs/developer-guide/working-with-rules#providing-suggestions)
+
+- Category: `Schema`
+- Rule name: `@graphql-eslint/require-nullable-result-in-root`
+- Requires GraphQL Schema: `true`
+  [ℹ️](/docs/getting-started#extended-linting-rules-with-graphql-schema)
+- Requires GraphQL Operations: `false`
+  [ℹ️](/docs/getting-started#extended-linting-rules-with-siblings-operations)
+
+Require nullable fields in root types.
+
+## Usage Examples
+
+### Incorrect
+
+```graphql
+# eslint @graphql-eslint/require-nullable-result-in-root: 'error'
+
+type Query {
+  user: User!
+}
+```
+
+### Correct
+
+```graphql
+# eslint @graphql-eslint/require-nullable-result-in-root: 'error'
+
+type Query {
+  foo: User
+  baz: [User]!
+  bar: [User!]!
+}
+```
+
+## Resources
+
+- [Rule source](https://github.com/B2o5T/graphql-eslint/tree/master/packages/plugin/src/rules/require-nullable-result-in-root.ts)
+- [Test source](https://github.com/B2o5T/graphql-eslint/tree/master/packages/plugin/tests/require-nullable-result-in-root.spec.ts)