nushell/crates/nu-protocol/src/value/custom_value.rs
Stefan Holderbach 62575c9a4f
Document and critically review ShellError variants - Ep. 3 (#8340)
Continuation of #8229 and #8326

# Description

The `ShellError` enum at the moment is kind of messy. 

Many variants are basic tuple structs where you always have to reference
the implementation with its macro invocation to know which field serves
which purpose.
Furthermore we have both variants that are kind of redundant or either
overly broad to be useful for the user to match on or overly specific
with few uses.

So I set out to start fixing the lacking documentation and naming to
make it feasible to critically review the individual usages and fix
those.
Furthermore we can decide to join or split up variants that don't seem
to be fit for purpose.

# Call to action

**Everyone:** Feel free to add review comments if you spot inconsistent
use of `ShellError` variants.

# User-Facing Changes

(None now, end goal more explicit and consistent error messages)

# Tests + Formatting

(No additional tests needed so far)

# Commits (so far)

- Remove `ShellError::FeatureNotEnabled`
- Name fields on `SE::ExternalNotSupported`
- Name field on `SE::InvalidProbability`
- Name fields on `SE::NushellFailed` variants
- Remove unused `SE::NushellFailedSpannedHelp`
- Name field on `SE::VariableNotFoundAtRuntime`
- Name fields on `SE::EnvVarNotFoundAtRuntime`
- Name fields on `SE::ModuleNotFoundAtRuntime`
- Remove usused `ModuleOrOverlayNotFoundAtRuntime`
- Name fields on `SE::OverlayNotFoundAtRuntime`
- Name field on `SE::NotFound`
2023-03-06 18:33:09 +01:00

60 lines
1.8 KiB
Rust

use std::{cmp::Ordering, fmt};
use crate::{ast::Operator, ShellError, Span, Value};
// Trait definition for a custom value
#[typetag::serde(tag = "type")]
pub trait CustomValue: fmt::Debug + Send + Sync {
fn clone_value(&self, span: Span) -> Value;
//fn category(&self) -> Category;
// Define string representation of the custom value
fn value_string(&self) -> String;
// Converts the custom value to a base nushell value
// This is used to represent the custom value using the table representations
// That already exist in nushell
fn to_base_value(&self, span: Span) -> Result<Value, ShellError>;
// Json representation of custom value
fn to_json(&self) -> nu_json::Value {
nu_json::Value::Null
}
// Any representation used to downcast object to its original type
fn as_any(&self) -> &dyn std::any::Any;
// Follow cell path functions
fn follow_path_int(&self, _count: usize, span: Span) -> Result<Value, ShellError> {
Err(ShellError::IncompatiblePathAccess {
type_name: self.value_string(),
span,
})
}
fn follow_path_string(&self, _column_name: String, span: Span) -> Result<Value, ShellError> {
Err(ShellError::IncompatiblePathAccess {
type_name: self.value_string(),
span,
})
}
// ordering with other value
fn partial_cmp(&self, _other: &Value) -> Option<Ordering> {
None
}
// Definition of an operation between the object that implements the trait
// and another Value.
// The Operator enum is used to indicate the expected operation
fn operation(
&self,
_lhs_span: Span,
operator: Operator,
op: Span,
_right: &Value,
) -> Result<Value, ShellError> {
Err(ShellError::UnsupportedOperator { operator, span: op })
}
}