Enforce require-selections on FragmentSpreads within GraphQLUnionTypes (#2319)

* Add failing test

* Support fragment spreads in union types in `require-selections`

* Add changeset

* upd snapshot

* more

* more

* more

* more

---------

Co-authored-by: Dimitri POSTOLOV <[email protected]>

Author: maciesielka

.changeset/empty-horses-relate.md

@@ -2,4 +2,6 @@
 '@graphql-eslint/eslint-plugin': patch
 ---
 
-fix false positive cases for `require-import-fragment` on Windows, when `graphql-config`'s `documents` key contained glob pattern => source file path of document contained always forward slashes
+fix false positive cases for `require-import-fragment` on Windows, when `graphql-config`'s
+`documents` key contained glob pattern => source file path of document contained always forward
+slashes

.changeset/empty-singers-develop.md

@@ -1,5 +1,5 @@
 ---
-"@graphql-eslint/eslint-plugin": minor
+'@graphql-eslint/eslint-plugin': minor
 ---
 
 feat: add a new option `{` for alphabetize rule to sort fields `selection set`

.changeset/twenty-tables-help.md

@@ -0,0 +1,5 @@
+---
+'@graphql-eslint/eslint-plugin': major
+---
+
+Enforce `require-selections` on `FragmentSpread`s within `GraphQLUnionType`s

packages/plugin/src/rules/require-selections/index.test.ts

@@ -7,12 +7,19 @@ const TEST_SCHEMA = /* GraphQL */ `
     noId: NoId!
     vehicles: [Vehicle!]!
     flying: [Flying!]!
+    noIdOrNoId2: NoIdOrNoId2!
   }
 
   type NoId {
     name: String!
   }
 
+  type NoId2 {
+    name: String!
+  }
+
+  union NoIdOrNoId2 = NoId | NoId2
+
   interface Vehicle {
     id: ID!
   }
@@ -310,6 +317,22 @@ ruleTester.run<RuleOptions, true>('require-selections', rule, {
       ...WITH_SCHEMA,
       code: '{ hasId {  id: name } }',
     },
+    {
+      name: 'should work when union has no `id` field to select',
+      ...WITH_SCHEMA,
+      code: /* GraphQL */ `
+        {
+          noIdOrNoId2 {
+            ... on NoId {
+              name
+            }
+            ... on NoId2 {
+              name
+            }
+          }
+        }
+      `,
+    },
   ],
   invalid: [
     {
@@ -429,5 +452,53 @@ ruleTester.run<RuleOptions, true>('require-selections', rule, {
         },
       },
     },
+    {
+      name: 'should report an error with union and non-inline fragment',
+      errors: [MESSAGE_ID],
+      code: /* GraphQL */ `
+        {
+          userOrPost {
+            ...UnionFragment
+          }
+        }
+      `,
+      parserOptions: {
+        graphQLConfig: {
+          schema: USER_POST_SCHEMA,
+          documents: /* GraphQL */ `
+            fragment UnionFragment on UserOrPost {
+              ... on User {
+                name
+              }
+            }
+          `,
+        },
+      },
+    },
+    {
+      name: 'should report an error with union and non-inline fragment and nested fragment',
+      errors: [MESSAGE_ID],
+      code: /* GraphQL */ `
+        {
+          userOrPost {
+            ...UnionFragment
+          }
+        }
+      `,
+      parserOptions: {
+        graphQLConfig: {
+          schema: USER_POST_SCHEMA,
+          documents: /* GraphQL */ `
+            fragment UnionFragment on UserOrPost {
+              ...UserFields
+            }
+
+            fragment UserFields on User {
+              name
+            }
+          `,
+        },
+      },
+    },
   ],
 });

packages/plugin/src/rules/require-selections/index.ts

@@ -171,12 +171,25 @@ export const rule: GraphQLESLintRule<RuleOptions, true> = {
         checkFields(rawType);
       } else if (rawType instanceof GraphQLUnionType) {
         for (const selection of node.selections) {
+          const types = rawType.getTypes();
           if (selection.kind === Kind.INLINE_FRAGMENT) {
-            const types = rawType.getTypes();
             const t = types.find(t => t.name === selection.typeCondition!.name.value);
             if (t) {
               checkFields(t);
             }
+          } else if (selection.kind === Kind.FRAGMENT_SPREAD) {
+            const [foundSpread] = siblings.getFragment(selection.name.value);
+            if (!foundSpread) return;
+            const fragmentSpread = foundSpread.document;
+
+            // the fragment is either for the union type itself or one of the types in the union
+            const t =
+              fragmentSpread.typeCondition.name.value === rawType.name
+                ? rawType
+                : types.find(t => t.name === fragmentSpread.typeCondition.name.value)!;
+            checkedFragmentSpreads.add(fragmentSpread.name.value);
+
+            checkSelections(fragmentSpread.selectionSet, t, loc, parent, checkedFragmentSpreads);
           }
         }
       }

packages/plugin/src/rules/require-selections/snapshot.md

@@ -170,6 +170,42 @@ exports[`require-selections > invalid > should report an error with union and fr
     7 |         }
 `;
 
+exports[`require-selections > invalid > should report an error with union and non-inline fragment 1`] = `
+#### ⌨️ Code
+
+      1 |         {
+      2 |           userOrPost {
+      3 |             ...UnionFragment
+      4 |           }
+      5 |         }
+
+#### ❌ Error
+
+      1 |         {
+    > 2 |           userOrPost {
+        |                      ^ Field \`userOrPost.id\` must be selected when it's available on a type.
+    Include it in your selection set or add to used fragment \`UnionFragment\`.
+      3 |             ...UnionFragment
+`;
+
+exports[`require-selections > invalid > should report an error with union and non-inline fragment and nested fragment 1`] = `
+#### ⌨️ Code
+
+      1 |         {
+      2 |           userOrPost {
+      3 |             ...UnionFragment
+      4 |           }
+      5 |         }
+
+#### ❌ Error
+
+      1 |         {
+    > 2 |           userOrPost {
+        |                      ^ Field \`userOrPost.id\` must be selected when it's available on a type.
+    Include it in your selection set or add to used fragments \`UnionFragment\` or \`UserFields\`.
+      3 |             ...UnionFragment
+`;
+
 exports[`require-selections > invalid > support multiple id field names 1`] = `
 #### ⌨️ Code