facebook/relay · error

Duplicate fragment definitions named {}: first one: {:?} s

Error message

Duplicate fragment definitions named {}: 
first one: {:?}
second one: {:?}

What it means

Panic while constructing a Program::from_definitions: two fragment definitions with the same name were collected; the location of both declarations is printed. Fragments are stored in a name-keyed map, so a duplicate makes the IR ambiguous and the build aborts.

Source

Thrown at compiler/crates/graphql-ir/src/program.rs:62

        let mut fragments = HashMap::default();
        let mut seen_operation_loc = HashMap::new();
        for definition in definitions {
            match definition {
                ExecutableDefinition::Operation(operation) => {
                    let loc = operation.name.location;
                    let name = operation.name.item;
                    if let Some(another) = seen_operation_loc.insert(name, loc) {
                        panic!(
                            "\nDuplicate operation definitions named {name}: \nfirst one: {loc:?}\nsecond one: {another:?}\n"
                        );
                    }
                    operations.push(Arc::new(operation)); // Keep the order the operations same as inputs.
                }
                ExecutableDefinition::Fragment(fragment) => {
                    let loc = fragment.name.location;
                    let name = fragment.name.item;
                    if let Some(another) = fragments.insert(name, Arc::new(fragment)) {
                        panic!(
                            "\nDuplicate fragment definitions named {}: \nfirst one: {:?}\nsecond one: {:?}\n",
                            name, loc, &another.name.location
                        );
                    }
                }
            }
        }
        Self {
            schema,
            fragments,
            operations,
        }
    }

    pub fn insert_fragment(&mut self, fragment: Arc<FragmentDefinition>) {
        let name = fragment.name.item;
        if let Some(previous) = self.fragments.insert(name, fragment) {
            panic!(

View on GitHub (pinned to 668b1b85e0)

Solutions

1. Rename one of the fragments or consolidate them into a single definition
2. Check for the same fragment file being included by overlapping source globs
3. Move project-specific fragments under their project root so names don't collide across projects

When it happens

Trigger: Thrown at compiler/crates/graphql-ir/src/program.rs:62 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of facebook/relay@668b1b85e0 (2026-09-02). Data as JSON: /api/errors/547bca64a7767307. Report an issue: GitHub.