dave
128 lines
4.3 KiB
Rust
128 lines
4.3 KiB
Rust
//! Typed validation error enum returned from all MCP write-tool input validation.
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use serde::{Deserialize, Serialize};
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use std::fmt;
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/// Structured error from input validation.
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///
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/// Each variant carries exactly the data a caller needs to act on the error.
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/// Serialises to serde's default externally-tagged form, e.g.
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/// `{"FieldTooLong":{"field":"description","max":200,"actual":287}}`.
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/// Callers can pattern-match on the JSON tag without parsing prose.
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#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
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pub enum ValidationError {
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/// A required field was absent from the input.
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FieldMissing { field: String },
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/// A field value is empty (or whitespace-only) after trimming.
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EmptyAfterTrim { field: String },
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/// A field value exceeds the maximum allowed length.
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FieldTooLong {
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field: String,
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max: usize,
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actual: usize,
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},
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/// A field value contains a character outside the allowed set.
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InvalidCharacter {
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field: String,
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ch: char,
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position: usize,
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},
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/// A field value contains a tool-call grammar fragment that must be rejected.
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AntiGrammarToken { field: String, token: String },
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/// A numeric field value is outside its allowed range.
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OutOfRange {
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field: String,
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min: i64,
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max: i64,
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actual: i64,
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},
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/// A list field has fewer items than the minimum.
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TooFewItems {
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field: String,
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min: usize,
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actual: usize,
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},
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/// A list field has more items than the maximum.
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TooManyItems {
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field: String,
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max: usize,
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actual: usize,
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},
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/// A field value is not valid UTF-8.
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InvalidUtf8 { field: String },
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/// A `depends_on` entry references the same item being created or updated.
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SelfReference { field: String },
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}
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impl fmt::Display for ValidationError {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::FieldMissing { field } => {
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write!(f, "field '{field}' is required but was not provided")
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}
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Self::EmptyAfterTrim { field } => {
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write!(f, "field '{field}' must not be empty or whitespace-only")
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}
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Self::FieldTooLong { field, max, actual } => {
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write!(f, "field '{field}' is too long ({actual} chars, max {max})")
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}
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Self::InvalidCharacter {
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field,
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ch,
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position,
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} => {
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write!(
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f,
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"field '{field}' contains invalid character {ch:?} at position {position}"
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)
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}
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Self::AntiGrammarToken { field, token } => {
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write!(
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f,
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"field '{field}' contains a tool-call grammar fragment: {token:?}"
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)
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}
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Self::OutOfRange {
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field,
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min,
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max,
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actual,
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} => {
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write!(
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f,
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"field '{field}' value {actual} is out of allowed range [{min}, {max}]"
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)
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}
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Self::TooFewItems { field, min, actual } => {
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write!(
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f,
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"field '{field}' has too few items ({actual}; minimum {min})"
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)
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}
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Self::TooManyItems { field, max, actual } => {
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write!(
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f,
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"field '{field}' has too many items ({actual}; maximum {max})"
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)
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}
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Self::InvalidUtf8 { field } => {
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write!(f, "field '{field}' contains invalid UTF-8")
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}
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Self::SelfReference { field } => {
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write!(
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f,
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"field '{field}' contains a self-reference (depends on itself)"
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)
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}
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}
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}
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}
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/// Serialise a slice of validation errors as a pretty-printed JSON string.
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///
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/// Used to turn `Vec<ValidationError>` into the `Err(String)` value returned by
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/// MCP tool handlers.
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pub fn format_errors_as_json(errors: &[ValidationError]) -> String {
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serde_json::to_string_pretty(errors).unwrap_or_else(|_| format!("{errors:?}"))
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}
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