What causes "Unable to process value" in denisidoro/navi?

Run the variable's underlying command manually and confirm it emits output containing the expected column

Unable to process value

Error message

Unable to process value

What it means

In the variable preview command (`preview var`), values that are not already plain env vars are computed by delegating to the finder pipeline via `finder::process`. The code `expect`s the result, so if the finder subprocess fails to parse/produce a value for the column, the preview panics with "Unable to process value".

Source

Thrown at src/commands/preview/var.rs:97

                "".to_string()
            };

            let replacement = format!(
                "{variable}",
                variable = style(bracketed_variable_name).with(variable_color),
            );

            colored_snippet = colored_snippet.replace(bracketed_variable_name, &replacement);

            variables = format!(
                "{variables}\n{variable} = {value}",
                variables = variables,
                variable = style(variable_name).with(variable_color),
                value = if env_var::get(&env_variable_name).is_ok() {
                    value
                } else if is_current {
                    finder::process(value, column, delimiter.as_deref(), map.clone())
                        .expect("Unable to process value")
                } else {
                    "".to_string()
                }
            );
        }

        println!("{snippet}", snippet = deser::fix_newlines(&colored_snippet));
        println!("{variables}");

        process::exit(0)
    }
}

View on GitHub (pinned to f7330b9ad5)

Solutions

Run the variable's underlying command manually and confirm it emits output containing the expected column
Check the variable's delimiter/column settings in the snippet config match the command output format
Verify the configured finder binary is installed and on PATH
Patch the preview code to surface `finder::process`'s error via `?` instead of panicking

Example fix

// before
finder::process(value, column, delimiter.as_deref(), map.clone()).expect("Unable to process value")
// after
finder::process(value, column, delimiter.as_deref(), map.clone())?

Defensive patterns

Strategy: validation

Validate before calling

let out = std::process::Command::new("sh").arg("-c").arg(&value).output()?;
if !out.status.success() || out.stdout.is_empty() {
    eprintln!("variable command produces no output; preview will fail");
}

Type guard

fn processable(value: &str, column: Option<usize>) -> bool {
    !value.trim().is_empty() && column.map_or(true, |c| value.split_whitespace().count() > c)
}

Try / catch

match finder::process(value, column, delimiter, map) {
    Ok(v) => v,
    Err(e) => { eprintln!("preview: cannot process value: {e}"); String::new() }
}

Prevention

Test dynamic variable commands manually before adding them to snippets
Make sure delimiter/column settings match the command's actual output
Keep the finder binary installed for preview to work
Run preview inside a TTY-capable terminal

When it happens

Trigger: Calling `preview` on a command/variable whose value requires finder processing (dynamic value with a column/delimiter) and `finder::process` returns `Err` — e.g. the underlying command fails, the delimiter/column doesn't match any output, or the finder binary errors.

Common situations: Previewing a variable whose dynamic command emits nothing (so column extraction fails); wrong `delimiter` configured for the snippet variable; finder binary missing or failing in the preview environment.

Related errors

AI-assisted analysis of denisidoro/navi@f7330b9ad5 (2026-09-03). Data as JSON: /api/errors/3c2de1750120b7e6. Report an issue: GitHub.