Enum DriverError 

pub enum DriverError {
    Builder {
        error: BuilderError,
    },
    Failed {
        report: Box<DriverReport>,
    },
    Help {
        text: String,
    },
    Completions {
        script: String,
    },
    Version {
        text: String,
    },
    EnvSubst {
        error: EnvSubstError,
    },
}

Reason the driver did not produce a parsed value.

This enum covers two distinct cases:

• Early exits (Help, Version, Completions) — the user asked for something other than running the program. These have exit code 0 and are “errors” only in the sense that no T was produced.

• Actual errors (Failed, Builder, EnvSubst) — something went wrong. These have exit code 1.

Most programs don’t need to inspect this type at all — calling DriverOutcome::unwrap() handles everything correctly. This type is useful when you want to customize behavior, e.g. in tests or in programs that embed figue’s parsing in a larger framework.

Exit Codes

Variant	Exit Code	Kind
Help	0	Early exit
Version	0	Early exit
Completions	0	Early exit
Failed	1	Error
Builder	1	Error
EnvSubst	1	Error

Example

use figue::{self as args, FigueBuiltins, DriverError};
use facet::Facet;

#[derive(Facet)]
struct Args {
    #[facet(args::positional, default)]
    file: Option<String>,

    #[facet(flatten)]
    builtins: FigueBuiltins,
}

// --help is an early exit, not an error
let err = figue::from_slice::<Args>(&["--help"]).unwrap_err();
assert!(err.is_success());
assert_eq!(err.exit_code(), 0);

// Pattern matching for custom handling:
match figue::from_slice::<Args>(&["--help"]).into_result() {
    Ok(output) => {
        // use output.value
    }
    Err(DriverError::Help { text }) => {
        assert!(text.contains("--help"));
        // print text and exit(0)
    }
    Err(DriverError::Version { text }) => {
        // print text and exit(0)
    }
    Err(DriverError::Failed { report }) => {
        // print report.render_pretty() and exit(1)
    }
    Err(e) => {
        // other error, exit(1)
    }
}

Variants

Builder

Builder failed (e.g., schema validation, file not found).

Exit code: 1

Fields

error: BuilderError

The builder error.

Failed

Parsing or validation failed.

Exit code: 1

The report contains detailed diagnostics with source locations when available.

Fields

report: Box<DriverReport>

Report containing all diagnostics.

Help

Help was requested (via #[facet(figue::help)] field).

Exit code: 0

This is a “successful” exit - the user asked for help and got it.

Fields

text: String

Formatted help text ready to print to stdout.

Completions

Shell completions were requested (via #[facet(figue::completions)] field).

Exit code: 0

This is a “successful” exit - the user asked for completions and got them.

Fields

script: String

Generated completion script for the requested shell.

Version

Version was requested (via #[facet(figue::version)] field).

Exit code: 0

This is a “successful” exit - the user asked for version and got it.

Fields

text: String

Version string (e.g., “myapp 1.0.0”).

EnvSubst

Environment variable substitution failed.

Exit code: 1

This happens when ${VAR} substitution is enabled but the variable is not set and has no default.

Fields

error: EnvSubstError

The substitution error.

Implementations

impl DriverError

pub fn exit_code(&self) -> i32

Returns the appropriate exit code for this error.

pub fn is_success(&self) -> bool

Returns true if this is a “success” error (help, completions, version).

pub fn is_help(&self) -> bool

Returns true if this is a help request.

pub fn help_text(&self) -> Option<&str>

Returns the help text if this is a help request.

Trait Implementations

impl Debug for DriverError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for DriverError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for DriverError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0: use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0: replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl Termination for DriverError

fn report(self) -> ExitCode

Is called to get the representation of the value as status code. This status code is returned to the operating system.