BoundaryML/baml · error · SourceRootError

dependency ` ` is declared twice

Error message

dependency `{name}` is declared twice

What it means

Part of the `SourceRootError` enum returned by `ProjectDatabase::add_source_root` / `add_dependency`. Thrown when the same dependency edge name is declared more than once on a single source root. Each package may have at most one edge per name; a second declaration is ambiguous and rejected.

Solutions

1. Deduplicate the `Vec<Dependency>` passed to `depending_on`, keeping one entry per `name`.
2. If two edges intentionally differ, give one a different alias `name`.
3. Check the manifest/source that produced the spec for repeated dependency entries.

Example fix

// before
spec.depending_on(vec![dep("core"), dep("core")])
// after
let mut seen = HashSet::new();
let deps: Vec<Dependency> = deps.into_iter().filter(|d| seen.insert(d.name.clone())).collect();
spec.depending_on(deps)

fn ensure_unique_names(deps: &[Dependency]) -> Result<(), String> {
    let mut seen = std::collections::HashSet::new();
    for d in deps {
        if !seen.insert(&d.name) { return Err(format!("duplicate dependency `{}`", d.name)); }
    }
    Ok(())
}

fn has_unique_names(deps: &[Dependency]) -> bool {
    deps.iter().map(|d| &d.name).collect::<std::collections::HashSet<_>>().len() == deps.len()
}

match db.add_source_root(spec) {
    Err(SourceRootError::DuplicateDependencyName { name }) => eprintln!("fix duplicate edge `{name}`"),
    Err(e) => eprintln!("other root error: {e}"),
    Ok(root) => root,
}

When it happens

Trigger: Calling `add_source_root` (or `add_dependency`) with a `SourceRootSpec` built via `depending_on` where two `Dependency` entries in the vector share the same `name`.

Common situations: Hand-written dependency lists built programmatically that append a name twice; manifest/tooling generation bugs that emit duplicate edges; merging two dependency lists without deduplication.

Understand the failure class

Background: Conflicting config options: "cannot be used together" — configuration validation errors across open-source libraries — this error's family across 162 libraries.

Related errors

• dependency ` ` names a source root that does not exist
• dependency ` ` would form a dependency cycle
• {0}
• {0}
• {0}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/3621373e38d4b522. Report an issue: GitHub.

Appendix: source

Thrown at baml_language/crates/baml_db/src/db.rs:94

        self.dependencies = dependencies;
        self
    }
}

/// Why [`ProjectDatabase::add_source_root`] or
/// [`ProjectDatabase::add_dependency`] refused.
#[derive(Debug, Clone, PartialEq, Eq, thiserror::Error)]
pub enum SourceRootError {
    /// A live root already sits at this (canonical) path.
    #[error("a source root already exists at this path")]
    PathTaken(SourceRoot),
    /// The edge name is one no package may declare: a stdlib package's name
    /// (already an implicit edge of every package) or a source-level
    /// qualifier (`root`, `env`).
    #[error("dependency name `{name}` is reserved")]
    ReservedDependencyName { name: Name },
    /// The root already has an edge under this name.
    #[error("dependency `{name}` is declared twice")]
    DuplicateDependencyName { name: Name },
    /// The edge names a root that is not live in this database.
    #[error("dependency `{name}` names a source root that does not exist")]
    UnknownDependencyRoot { name: Name },
    /// The edge would make the dependency graph cyclic.
    #[error("dependency `{name}` would form a dependency cycle")]
    DependencyCycle { name: Name },
    /// The interface bytes are not a valid `PackageInterface` artifact.
    #[error("invalid package interface: {message}")]
    InvalidInterface { message: String },
}

/// The main database for BAML projects.
///
/// `ProjectDatabase` owns the Salsa storage directly and implements all the
/// compiler `Db` traits. It provides high-level APIs for:
/// - Source-root management (add/remove roots, longest-prefix lookup)
/// - File management within a root (add/update/remove files)

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