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

unexpected {btype} bracket `{literal}` in build.build-dir pa

Error message

unexpected {btype} bracket `{literal}` in build.build-dir path `{raw_template}`

What it means

Raised in the same `resolve_templated_path` call (src/workspace/workspace.rs:384) when the lockfile-path contains an unmatched/unbalanced brace — `ResolveTemplateError::UnexpectedBracket` with `BracketType::Opening` (`{`) or `Closing` (`}`). The message reports whether the stray character is an opening or closing bracket and shows the raw template. Note the message string hard-codes 'build.build-dir path' even though it fires for `resolver.lockfile-path`.

Source

Thrown at src/workspace/workspace.rs:390

            let replacements: [(&str, &str); 0] = [];
            let path = lockfile_path
                    .resolve_templated_path(self.gctx(), replacements)
                    .map_err(|e| match e {
                        context::ResolveTemplateError::UnexpectedVariable {
                            variable,
                            raw_template,
                        } => {
                            anyhow!(
                                "unexpected variable `{variable}` in resolver.lockfile-path `{raw_template}`"
                            )
                        }
                        context::ResolveTemplateError::UnexpectedBracket { bracket_type, raw_template } => {
                            let (btype, literal) = match bracket_type {
                                context::BracketType::Opening => ("opening", "{"),
                                context::BracketType::Closing => ("closing", "}"),
                            };

                            anyhow!(
                                "unexpected {btype} bracket `{literal}` in build.build-dir path `{raw_template}`"
                            )
                        }
                    })?;
            if !path.ends_with(LOCKFILE_NAME) {
                bail!("the `resolver.lockfile-path` must be a path to a {LOCKFILE_NAME} file");
            }
            if path.is_dir() {
                bail!(
                    "`resolver.lockfile-path` `{}` is a directory but expected a file",
                    path.display()
                );
            }
            self.requested_lockfile_path = Some(path);
        }

        Ok(())
    }

View on GitHub (pinned to 0e07a15537)

Solutions

1. Balance or remove the stray `{` / `}` in the `resolver.lockfile-path` value.
2. If the brace was meant literally (rare), choose a path without brace characters.
3. Re-read the raw value from the config file the error references and fix it there.

Example fix

# before
[resolver]
lockfile-path = "${HOME}/Cargo.lock"
# after — use a real path, no shell/brace syntax
[resolver]
lockfile-path = "/home/user/Cargo.lock"

fn balanced_braces(s: &str) -> bool {
    let mut depth = 0i32;
    for c in s.chars() { match c { '{' => depth += 1, '}' => { depth -= 1; if depth < 0 { return false; } } _ => {} } }
    depth == 0
}
// assert balanced_braces(&lockfile_path) and no stray braces

When it happens

Trigger: A `resolver.lockfile-path` value containing a lone `{` or `}` (e.g. `"{Cargo.lock"`, `"dir/}x"`, or a literal brace intended as a filename).

Common situations: Hand-editing config and leaving an unclosed brace; pasting a Windows path with brace characters; an editor auto-inserting a closing brace in the wrong place; shell variable leftovers like `${HOME}/Cargo.lock`.

Related errors

• unexpected variable `{variable}` in resolver.lockfile-path `
• unexpected {btype} bracket `{literal}` in build.build-dir pa
• subcommand is required, add a subcommand to the command alia
• alias {} has unresolvable recursive definition: {} -> {}
• subcommand is required, but `{alias_name}` is empty

AI-assisted analysis of rust-lang/cargo@0e07a15537 (2026-08-06). Data as JSON: /data/errors/dcf04f996d6ef87f.json. Report an issue: GitHub.