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Error Types

Hornet defines its error types in hornet_bind9::error.

Error

The main error type returned by all parse and IO functions.

pub enum Error {
    /// A syntax error encountered while parsing.
    Parse {
        file: String,
        message: String,
        src: miette::NamedSource<String>,
        span: miette::SourceSpan,
    },

    /// A semantic validation finding.
    Validation(ValidationError),

    /// An IO error reading a file.
    Io(std::io::Error),

    /// An error serialising the AST to text.
    Write(String),
}

Error::Parse

Returned by parse_named_conf, parse_named_conf_source, parse_named_conf_file, parse_zone_file, parse_zone_file_source and parse_zone_file_from_path when the input text does not conform to the grammar.

Fields:

Field Type Description
file String Source name: the path for the file functions, the source_name argument for the _source functions, or <input> for plain string input
message String Human-readable description of the parse failure
src miette::NamedSource<String> Source text, named like file, for pretty-printing
span miette::SourceSpan Location of the failure (currently the start of the source)

Zone-file parsing returns Error::Parse for any logical line that is neither a record nor a known directive: an unknown $ directive, a bad $TTL value, a line with no record type, or a bad owner name. The message names the line:

line 7: cannot parse `$BOGUS 1`

Record data that does not match its type is not a parse error; it is kept verbatim and reported by the validator (see below).

Error::Io

Wraps std::io::Error. Returned by parse_named_conf_file and parse_zone_file_from_path when the file cannot be read (not found, permission denied, etc.).

Result

Type alias for std::result::Result<T, Error>:

pub type Result<T> = std::result::Result<T, Error>;

ValidationError

Returned (in a Vec) by validate_named_conf and validate_zone_file.

pub struct ValidationError {
    pub severity: Severity,
    pub message: String,
    pub location: Option<ErrorLocation>,
}
Field Type Description
severity Severity Diagnostic severity level
message String Human-readable description
location Option<ErrorLocation> Source location (line/column), if available

Zone-file diagnostics

validate_zone_file emits these messages (<...> marks substituted values):

error:   Zone file is missing a SOA record
error:   Multiple SOA records found in zone file
error:   Zone file is missing NS records
error:   TXT record data exceeds 65535 bytes
warning: TXT string of <N> bytes exceeds 255-byte chunk limit
warning: MX exchange is '.' which means no mail server
warning: CAA tag "<tag>" is not a standard tag
warning: <TYPE> record data `<data>` is not valid <TYPE> syntax; kept verbatim

The last warning is new in 0.2.0. It fires for an RData::Unknown record whose rtype is listed in hornet_bind9::ast::zone_file::MODELLED_RTYPES: the parser kept data it could not read for that type instead of dropping the record.

Severity

#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
pub enum Severity {
    Info,
    Warning,
    Error,
}

Severity implements PartialOrd: Info < Warning < Error.

Variant Meaning
Info Informational; best-practice reminder
Warning Suspicious configuration; BIND9 will load but may behave unexpectedly
Error Definite misconfiguration; BIND9 will likely refuse to start

ErrorLocation

Optional source location attached to a ValidationError.

pub struct ErrorLocation {
    pub line: usize,
    pub column: usize,
}

Note

Most validation diagnostics currently have location: None. Source location tracking is planned for a future release.

Working with miette

Error::Parse implements miette::Diagnostic, enabling pretty-printed error output with syntax highlighting when using miette::IntoDiagnostic:

fn main() -> miette::Result<()> {
    let conf = hornet_bind9::parse_named_conf_file(path)?;
    Ok(())
}

Graphical rendering needs miette's fancy feature, which hornet enables only with its cli feature (since 0.3.0); add features = ["fancy"] to your own miette dependency to get it.

The diagnostic code is hornet_bind9::parse, and the source shown is named after the file field. The highlighted span currently points at the start of the source; zone-file errors carry the line number in their message.

Next Steps