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use std::fmt;
/// Errors returned while constructing or evaluating a robot model.
#[derive(Debug)]
#[non_exhaustive]
pub enum Error {
/// The URDF file could not be read or parsed.
Urdf(urdf_rs::UrdfError),
/// The URDF describes an invalid or unsupported kinematic graph.
InvalidModel(String),
/// A joint uses a motion type not supported by this crate.
UnsupportedJointType {
/// Name of the joint using the unsupported type.
joint: String,
/// Unsupported URDF joint type.
joint_type: String,
},
/// A runtime-sized input or output has the wrong length.
WrongSliceLength {
/// Name of the rejected input or output.
slice: &'static str,
/// Required number of elements.
expected: usize,
/// Number of elements supplied by the caller.
actual: usize,
},
/// A joint axis is too small to normalize.
InvalidJointAxis {
/// Name of the joint with the invalid axis.
joint: String,
},
/// No link with the requested name exists in the model.
UnknownLink {
/// Link name requested by the caller.
name: String,
},
/// A link identifier belongs to a different robot model.
InvalidLinkId,
/// A workspace belongs to a different robot model or has the wrong size.
InvalidWorkspace,
/// A base-state component is invalid.
InvalidBaseState {
/// Name of the rejected component.
field: &'static str,
/// Constraint violated by the component.
reason: &'static str,
},
/// Inverse kinematics is not defined for floating-base robots.
FloatingBaseIkUnsupported,
/// One of the inverse-kinematics options is zero, negative, or non-finite.
InvalidIkOptions {
/// Name of the rejected option.
option: &'static str,
/// Constraint violated by the option.
reason: &'static str,
},
/// An inverse-kinematics input contains a non-finite value.
NonFiniteIkInput {
/// Name of the input containing a non-finite value.
input: &'static str,
},
/// The inverse-kinematics damped linear system could not be solved.
IkNumericalFailure {
/// One-based iteration at which the numerical solve failed.
iteration: usize,
},
/// A converged inverse-kinematics solution violates a joint limit.
IkJointLimitViolation {
/// Zero-based index of the joint.
joint_index: usize,
/// Name of the joint.
joint: String,
/// Position produced by the solver.
position: f64,
/// Minimum permitted position.
lower: f64,
/// Maximum permitted position.
upper: f64,
},
/// Inverse kinematics did not reach the requested pose within its iteration budget.
IkNotConverged {
/// Number of joint updates attempted.
iterations: usize,
/// Final Euclidean translation error, in metres.
translation_error: f64,
/// Final rotation-vector norm, in radians.
rotation_error: f64,
},
}
/// Stable, coarse classification of errors for language bindings and callers.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum ErrorCategory {
/// The caller supplied an invalid name, handle, buffer, option, or value.
InvalidInput,
/// A robot description could not be loaded or represented.
Model,
/// An iterative numerical calculation failed to produce a valid result.
Solver,
}
impl Error {
/// Returns a stable category suitable for mapping into a foreign-language API.
pub const fn category(&self) -> ErrorCategory {
match self {
Self::Urdf(_)
| Self::InvalidModel(_)
| Self::UnsupportedJointType { .. }
| Self::InvalidJointAxis { .. } => ErrorCategory::Model,
Self::WrongSliceLength { .. }
| Self::UnknownLink { .. }
| Self::InvalidLinkId
| Self::InvalidWorkspace
| Self::InvalidBaseState { .. }
| Self::FloatingBaseIkUnsupported
| Self::InvalidIkOptions { .. }
| Self::NonFiniteIkInput { .. } => ErrorCategory::InvalidInput,
Self::IkNumericalFailure { .. }
| Self::IkJointLimitViolation { .. }
| Self::IkNotConverged { .. } => ErrorCategory::Solver,
}
}
}
impl fmt::Display for Error {
/// Formats a human-readable description of the model or calculation error.
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::Urdf(error) => write!(f, "failed to parse URDF: {error}"),
Self::InvalidModel(message) => write!(f, "invalid robot model: {message}"),
Self::UnsupportedJointType { joint, joint_type } => {
write!(f, "joint {joint} uses unsupported type {joint_type}")
}
Self::WrongSliceLength {
slice,
expected,
actual,
} => write!(f, "expected {expected} elements in {slice}, found {actual}"),
Self::InvalidJointAxis { joint } => write!(f, "joint {joint} has an invalid axis"),
Self::UnknownLink { name } => write!(f, "link {name} does not exist in the model"),
Self::InvalidLinkId => write!(f, "link identifier does not belong to this robot model"),
Self::InvalidWorkspace => {
write!(f, "workspace does not belong to this robot model")
}
Self::InvalidBaseState { field, reason } => {
write!(f, "invalid base {field}: {reason}")
}
Self::FloatingBaseIkUnsupported => {
write!(f, "inverse kinematics does not support a floating base")
}
Self::InvalidIkOptions { option, reason } => {
write!(f, "invalid inverse-kinematics option {option}: {reason}")
}
Self::NonFiniteIkInput { input } => {
write!(f, "inverse-kinematics {input} contains a non-finite value")
}
Self::IkNumericalFailure { iteration } => write!(
f,
"inverse-kinematics linear solve failed at iteration {iteration}"
),
Self::IkJointLimitViolation {
joint_index,
joint,
position,
lower,
upper,
} => write!(
f,
"inverse-kinematics solution {position:.6e} for joint {joint_index} ({joint}) \
is outside URDF limits [{lower:.6e}, {upper:.6e}]"
),
Self::IkNotConverged {
iterations,
translation_error,
rotation_error,
} => write!(
f,
"inverse kinematics did not converge after {iterations} iterations \
(translation error {translation_error:.6e}, rotation error {rotation_error:.6e})"
),
}
}
}
impl std::error::Error for Error {
/// Returns the underlying URDF error, when present.
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
match self {
Self::Urdf(error) => Some(error),
_ => None,
}
}
}
impl From<urdf_rs::UrdfError> for Error {
/// Wraps a URDF parser error in the crate's general error type.
fn from(value: urdf_rs::UrdfError) -> Self {
Self::Urdf(value)
}
}
/// Result type returned by robot-model construction and calculations.
pub type Result<T> = std::result::Result<T, Error>;
#[cfg(test)]
mod tests {
use super::{Error, ErrorCategory};
#[test]
fn display_describes_each_library_error_and_has_no_source() {
let cases = [
(
Error::InvalidModel("broken tree".to_owned()),
"invalid robot model: broken tree".to_owned(),
),
(
Error::UnsupportedJointType {
joint: "floating_base".to_owned(),
joint_type: "floating".to_owned(),
},
"joint floating_base uses unsupported type floating".to_owned(),
),
(
Error::WrongSliceLength {
slice: "q",
expected: 4,
actual: 3,
},
"expected 4 elements in q, found 3".to_owned(),
),
(
Error::InvalidJointAxis {
joint: "shoulder".to_owned(),
},
"joint shoulder has an invalid axis".to_owned(),
),
(
Error::UnknownLink {
name: "tool".to_owned(),
},
"link tool does not exist in the model".to_owned(),
),
(
Error::InvalidLinkId,
"link identifier does not belong to this robot model".to_owned(),
),
(
Error::InvalidWorkspace,
"workspace does not belong to this robot model".to_owned(),
),
(
Error::InvalidBaseState {
field: "velocity",
reason: "must be finite",
},
"invalid base velocity: must be finite".to_owned(),
),
(
Error::FloatingBaseIkUnsupported,
"inverse kinematics does not support a floating base".to_owned(),
),
(
Error::InvalidIkOptions {
option: "damping",
reason: "must be positive",
},
"invalid inverse-kinematics option damping: must be positive".to_owned(),
),
(
Error::NonFiniteIkInput {
input: "target frame",
},
"inverse-kinematics target frame contains a non-finite value".to_owned(),
),
(
Error::IkNumericalFailure { iteration: 3 },
"inverse-kinematics linear solve failed at iteration 3".to_owned(),
),
(
Error::IkJointLimitViolation {
joint_index: 2,
joint: "elbow".to_owned(),
position: 1.5,
lower: -1.0,
upper: 1.0,
},
"inverse-kinematics solution 1.500000e0 for joint 2 (elbow) is outside URDF limits [-1.000000e0, 1.000000e0]".to_owned(),
),
(
Error::IkNotConverged {
iterations: 4,
translation_error: 0.25,
rotation_error: 0.5,
},
"inverse kinematics did not converge after 4 iterations (translation error 2.500000e-1, rotation error 5.000000e-1)".to_owned(),
),
];
for (error, expected) in cases {
assert_eq!(error.to_string(), expected);
assert!(std::error::Error::source(&error).is_none());
}
}
#[test]
fn categories_group_errors_by_caller_action() {
assert_eq!(
Error::InvalidModel("broken tree".to_owned()).category(),
ErrorCategory::Model
);
assert_eq!(
Error::WrongSliceLength {
slice: "q",
expected: 4,
actual: 3,
}
.category(),
ErrorCategory::InvalidInput
);
assert_eq!(
Error::IkNotConverged {
iterations: 4,
translation_error: 0.25,
rotation_error: 0.5,
}
.category(),
ErrorCategory::Solver
);
}
}