rust-lang/cargo · error · anyhow::Error

invalid `package.build` file name

Error message

invalid `package.build` file name

What it means

Error "invalid `package.build` file name" thrown in rust-lang/cargo.

Source

Thrown at src/workspace/parser/targets.rs:1136

                "`build_file` started as a String and `normalize_path` shouldn't have changed that",
            );
            Ok(Some(TomlPackageBuild::SingleScript(build)))
        }
        Some(TomlPackageBuild::Auto(true)) => {
            Ok(Some(TomlPackageBuild::SingleScript(BUILD_RS.to_owned())))
        }
        Some(TomlPackageBuild::MultipleScript(scripts)) => {
            for script in scripts {
                validate_build_name(script)?;
            }
            Ok(build.cloned())
        }
    }
}

fn validate_build_name(build: &str) -> CargoResult<()> {
    if Path::new(build).file_stem().is_none() {
        anyhow::bail!("invalid `package.build` file name");
    }
    Ok(())
}

fn name_or_panic(target: &TomlTarget) -> &str {
    target
        .name
        .as_deref()
        .unwrap_or_else(|| panic!("target name is required"))
}

fn validate_lib_name(target: &TomlTarget, warnings: &mut Vec<String>) -> CargoResult<()> {
    validate_target_name(target, TARGET_KIND_HUMAN_LIB, TARGET_KIND_LIB, warnings)?;
    let name = name_or_panic(target);
    if name.contains('-') {
        anyhow::bail!("library target names cannot contain hyphens: {}", name)
    }

View on GitHub (pinned to 0e07a15537)

Solutions

1. Use a valid file name for `package.build`, e.g. `build = "build.rs"` or another valid `.rs` path.
2. Remove the `build` key to use the default `build.rs`.

When it happens

Trigger: Thrown at src/workspace/parser/targets.rs:1136 when the library encounters an invalid state.

Common situations: Occurs when `package.build` points to a file with an invalid name. Use a valid file name such as `build.rs` or a custom path like `build/main.rs`.

AI-assisted analysis of rust-lang/cargo@0e07a15537 (2026-08-06). Data as JSON: /data/errors/e00d62de0e56e950.json. Report an issue: GitHub.