feat(compiler): allow SDL to contain built-in type redefinition

crates/apollo-compiler/CHANGELOG.md

@@ -21,14 +21,20 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## Features
 
-- **Adds `ignore_builtin_redefinitions` option to `SchemaBuilder` to allow SDL to contain built-in
-  scalar definitions - [dariuszkuc], [pull/990]**
+- **Adds `ignore_builtin_redefinitions` option to `SchemaBuilder` to allow SDL to contain built-in type
+  definitions - [dariuszkuc], [pull/990] and [pull/994]**
 
 ## Fixes
 
-- **Fix handling of orphan root type extensions - [dariuszkuc], [pull/993]**
-- **Fix possible stack overflow in validation of directive definition arguments with nested types - [dariuszkuc], [pull/987]**
-- **Fix `iter_origin()` to be a pub method- [duckki], [pull/989]**
+- **Fix handling of orphan root type extensions - [dariuszkuc], [pull/993](#993)**
+- **Fix possible stack overflow in validation of directive definition arguments with nested types - [dariuszkuc], [pull/987](#987)**
+- **Fix `iter_origin()` to be a pub method- [duckki], [pull/989](#989)**
+
+[pull/994]: https://github.com/apollographql/apollo-rs/pull/994
+[pull/993]: https://github.com/apollographql/apollo-rs/pull/993
+[pull/990]: https://github.com/apollographql/apollo-rs/pull/990
+[pull/989]: https://github.com/apollographql/apollo-rs/pull/989
+[pull/987]: https://github.com/apollographql/apollo-rs/pull/987
 
 # [1.29.0](https://crates.io/crates/apollo-compiler/1.29.0) - 2025-08-08
 

crates/apollo-compiler/src/schema/from_ast.rs

@@ -134,15 +134,15 @@ impl SchemaBuilder {
                         }
                         Entry::Occupied(entry) => {
                             let previous = entry.get();
+                            if self.ignore_builtin_redefinitions && previous.is_built_in() {
+                                continue;
+                            }
+
                             if $is_scalar && previous.is_built_in() {
-                                if self.ignore_builtin_redefinitions {
-                                    continue;
-                                } else {
-                                    self.errors.push(
-                                        $def.location(),
-                                        BuildError::BuiltInScalarTypeRedefinition,
-                                    )
-                                }
+                                self.errors.push(
+                                    $def.location(),
+                                    BuildError::BuiltInScalarTypeRedefinition,
+                                )
                             } else {
                                 self.errors.push(
                                     $def.name.location(),

crates/apollo-compiler/tests/validation/types.rs

@@ -2020,7 +2020,7 @@ mod variable_default_values {
 }
 
 #[test]
-fn handles_built_in_type_redefinition() {
+fn handles_built_in_scalar_redefinition() {
     let schema = r#"
 scalar String
 
@@ -2049,3 +2049,48 @@ type Query {
         .build()
         .expect("schema parsed successfully");
 }
+
+#[test]
+fn handles_built_in_type_redefinition() {
+    let schema = r#"
+type __Directive {
+  name: String!
+  description: String!
+  isRepeatable: String!
+  args: __InputValue
+  locations: String!
+}
+
+type Query {
+  foo: String
+}
+"#;
+
+    let errors = Schema::parse_and_validate(schema, "schema.graphql")
+        .expect_err("invalid schema")
+        .errors;
+    let expected = expect![[r#"
+        Error: the type `__Directive` is defined multiple times in the schema
+            ╭─[ built_in.graphql:87:6 ]
+            │
+         87 │ type __Directive {
+            │      ─────┬─────  
+            │           ╰─────── previous definition of `__Directive` here
+            │
+            ├─[ schema.graphql:2:6 ]
+            │
+          2 │ type __Directive {
+            │      ─────┬─────  
+            │           ╰─────── `__Directive` redefined here
+            │ 
+            │ Help: remove or rename one of the definitions, or use `extend`
+        ────╯
+    "#]];
+    expected.assert_eq(&errors.to_string());
+
+    let builder = SchemaBuilder::new().ignore_builtin_redefinitions();
+    let _ = builder
+        .parse(schema, "schema.graphql")
+        .build()
+        .expect("schema parsed successfully");
+}