Struct FilterValidator 

pub struct FilterValidator {
    pub allowed_fields: Vec<String>,
    pub denied_operators: Vec<Operator>,
    pub max_depth: usize,
}

Validation configuration for user-provided filters.

Provides four layers of security:

1. Field whitelist - only specific fields can be queried
2. Operator blacklist - dangerous operators can be denied
3. Nesting depth limit - prevent complex nested queries
4. Total node count limit - prevent DoS via large arrays

Fields

allowed_fields: Vec<String>

Allowed field names (whitelist). Empty = allow all fields.

denied_operators: Vec<Operator>

Denied operators (blacklist).

max_depth: usize

Maximum nesting depth for complex filters.

Implementations

impl FilterValidator

pub fn new() -> Self

Create a new validator with secure defaults.

Defaults:

• No field restrictions (allow all)
• Denies Regex operator (ReDoS prevention)
• Max nesting depth: 5

This is the recommended constructor for user-facing filters. For internal/trusted filters where you need all operators, use permissive().

Example

use mik_sql::FilterValidator;

let validator = FilterValidator::new()
    .allow_fields(&["name", "email", "status"]);

pub fn permissive() -> Self

Create a permissive validator that allows all operators.

Warning: Only use this for trusted/internal filters, never for user-provided input. The Regex operator can cause ReDoS attacks.

Example

use mik_sql::FilterValidator;

// Only for trusted internal filters!
let validator = FilterValidator::permissive();

pub fn allow_fields(self, fields: &[&str]) -> Self

Set allowed fields (whitelist).

Only fields in this list can be used in user filters. If empty, all fields are allowed.

pub fn deny_operators(self, ops: &[Operator]) -> Self

Set denied operators (blacklist).

These operators cannot be used in user filters. Useful for blocking regex, pattern matching, or other expensive operations.

pub fn max_depth(self, depth: usize) -> Self

Set maximum nesting depth.

Prevents complex nested queries that could impact performance. Default is 5.

pub fn validate(&self, filter: &Filter) -> Result<(), ValidationError>

Validate a filter against the configured rules.

Returns an error if:

• Field is not in the allowed list (when list is not empty)
• Operator is in the denied list
• Array nesting depth exceeds maximum

Trait Implementations

impl Clone for FilterValidator

fn clone(&self) -> FilterValidator

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FilterValidator

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

Formats the value using the given formatter.

impl Default for FilterValidator

fn default() -> Self

Returns the “default value” for a type.