BoundaryML/baml · info

no-color diagnostics do not invoke the message highlighter

Error message

no-color diagnostics do not invoke the message highlighter

What it means

In render_diagnostics_with_highlighters, when the DiagnosticFormat is human but color is disabled, the code renders with None as the message highlighter. Because no-color output never applies semantic message highlighting, the call is asserted infallible with this expect. It is an internal invariant: supplying no highlighter to the no-color path cannot produce a highlighting error.

Source

Thrown at baml_language/crates/baml_compiler_diagnostics/src/render.rs:221

                    file_paths,
                    &handler,
                    config.color,
                    config.show_error_codes,
                    message_highlighter,
                ) {
                    Ok(output) => output,
                    Err(DiagnosticMessageHighlightError) => {
                        let handler = miette_handler(None, false, diagnostic.severity);
                        render_miette_with_handler(
                            diagnostic,
                            sources,
                            file_paths,
                            &handler,
                            false,
                            config.show_error_codes,
                            None,
                        )
                        .expect("no-color diagnostics do not invoke the message highlighter")
                    }
                }
            }
            DiagnosticFormat::Agent => render_agent(
                diagnostic,
                sources,
                file_paths,
                &mut path_cache,
                config.color,
                config.show_error_codes,
            ),
            DiagnosticFormat::Concise => render_concise(diagnostic, sources, file_paths),
        })
        .collect::<Vec<_>>()
        .join("\n")
}

#[derive(Debug)]

View on GitHub (pinned to bd85ce9dee)

Solutions

1. No user action required; the assertion protects an internal invariant.
2. If it panics, you are running a modified build: revert renderer changes so the no-color branch passes None with syntax highlighting disabled.
3. Replace the expect with proper error propagation if you intentionally add highlighting to the no-color path.

let out = std::panic::catch_unwind(|| render_diagnostics_with_highlighters(&diag, &sources, &cfg, highlighter));
if out.is_err() { /* fall back to plain no-color rendering */ }

When it happens

Trigger: Never from user code directly: it fires only if render with a None highlighter and color=false unexpectedly returns Err inside the human-format branch of render_diagnostics_with_highlighters.

Common situations: A developer would only see this while hacking on the renderer itself — e.g. changing miette handler configuration so the no-color path still attempts semantic highlighting and fails.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• rendering without a message highlighter cannot fail semantic
• writing to a String cannot fail
• colored diagnostics have a source highlighter
• diagnostic message style code is a valid Unicode variation s
• Package.current call site names a loaded package

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/2283837ead950240. Report an issue: GitHub.