Pass if type implements reachable interface (#319)

Co-authored-by: Kamil Kisiela <[email protected]>

Author: gilgardosh

.changeset/spotty-lies-hang.md

@@ -0,0 +1,5 @@
+---
+'@graphql-eslint/eslint-plugin': patch
+---
+
+no-unreachable-types pass if type implements reachable interface

packages/plugin/src/rules/no-unreachable-types.ts

@@ -48,16 +48,17 @@ const rule: GraphQLESLintRule = {
   create(context) {
     function ensureReachability(node) {
       const typeName = node.name.value;
+      const implemented = node.interfaces?.map(instance => instance.name.value) || [];
       const reachableTypes = requireReachableTypesFromContext('no-unreachable-types', context);
 
-      if (!reachableTypes.has(typeName)) {
+      if (!reachableTypes.has(typeName) && implemented.filter(name => reachableTypes.has(name)).length === 0) {
         context.report({
           node,
           messageId: UNREACHABLE_TYPE,
           data: {
             typeName,
           },
-          fix: fixer => fixer.removeRange(node.range)
+          fix: fixer => fixer.removeRange(node.range),
         });
       }
     }

packages/plugin/tests/no-unreachable-types.spec.ts

@@ -30,7 +30,6 @@ ruleTester.runGraphQLTests('no-unreachable-types', rule, {
         name: String
       }
     `),
-
     useSchema(/* GraphQL */ `
       type Query {
         me: User
@@ -44,6 +43,39 @@ ruleTester.runGraphQLTests('no-unreachable-types', rule, {
         city: String
       }
     `),
+    useSchema(/* GraphQL */ `
+      type Query {
+        me: User!
+      }
+
+      interface User {
+        name: String
+      }
+
+      type SuperUser implements User {
+        address: String
+      }
+    `),
+    useSchema(/* GraphQL */ `
+      type Query {
+        node(id: ID!): Node!
+      }
+
+      interface Node {
+        id: ID!
+      }
+
+      interface User implements Node {
+        id: ID!
+        name: String
+      }
+
+      type SuperUser implements User & Node {
+        id: ID!
+        name: String
+        address: String
+      }
+    `),
   ],
   invalid: [
     {
@@ -186,5 +218,60 @@ ruleTester.runGraphQLTests('no-unreachable-types', rule, {
         },
       ],
     },
+    {
+      ...useSchema(/* GraphQL */ `
+        # normalize graphql
+
+        type Query {
+          node(id: ID!): User
+        }
+
+        interface User implements Node {
+          id: ID!
+          name: String
+        }
+
+        interface Node {
+          id: ID!
+        }
+
+        interface Missing {
+          mid: ID!
+        }
+
+        type SuperUser implements User & Node {
+          id: ID!
+          name: String
+          isSuper: Boolean!
+        }
+      `),
+      output: /* GraphQL */ `
+        # normalize graphql
+
+        type Query {
+          node(id: ID!): User
+        }
+
+        interface User implements Node {
+          id: ID!
+          name: String
+        }
+
+        interface Node {
+          id: ID!
+        }
+
+        type SuperUser implements User & Node {
+          id: ID!
+          name: String
+          isSuper: Boolean!
+        }
+      `,
+      errors: [
+        {
+          message: `Type "Missing" is unreachable`,
+        },
+      ],
+    },
   ],
 });