std-validation

Reusable composable validation rules

Package: std.validation Version: 0.1.0 Capabilities required: none

Overview

std-validation provides a small set of pure, composable validation functions. Each returns a ValidationResult that carries a pass/fail flag and an error message. Chain results with validation_merge to apply multiple rules in sequence and surface the first failure. std-forms depends on this library for field-level validation.

Installation

Add to your package.ax.json dependencies:

"std.validation": "0.1.0"

API Reference

Types

ValidationError

type ValidationError { field: String, message: String }

ValidationResult

type ValidationResult { valid: Int, error_field: String, error_message: String }

• valid — 1 if the rule passed, 0 if it failed
• error_field — the field name on failure, "" on success
• error_message — a short description of what failed, "" on success

Functions

String rules

validate_required(field: String, value: String) -> ValidationResult

Fails if value is an empty string.

Example

fn main() -> Int {
  let r: ValidationResult = validate_required("email", "")
  r.valid
}

validate_not_empty(field: String, value: String) -> ValidationResult

Alias for validate_required.

validate_min_length(field: String, value: String, min: Int) -> ValidationResult

Fails if the string length is less than min.

validate_max_length(field: String, value: String, max: Int) -> ValidationResult

Fails if the string length exceeds max.

validate_numeric(field: String, value: String) -> ValidationResult

Fails if value cannot be parsed as an integer.

validate_equals(field: String, actual: String, expected: String) -> ValidationResult

Fails if actual != expected. Use for password confirmation fields.

Integer rules

validate_min_value(field: String, value: Int, min: Int) -> ValidationResult

Fails if value < min.

validate_max_value(field: String, value: Int, max: Int) -> ValidationResult

Fails if value > max.

Composition

validation_ok() -> ValidationResult

Returns a pre-built passing result. Use as the initial accumulator in a chain.

validation_fail(field: String, message: String) -> ValidationResult

Returns a pre-built failing result with a custom message.

validation_merge(a: ValidationResult, b: ValidationResult) -> ValidationResult

Returns a if it failed, otherwise returns b. Use to apply rules in priority order and surface the first failure.

Example: chaining multiple rules

fn main() -> Int {
  let r1: ValidationResult = validate_required("username", "alice")
  let r2: ValidationResult = validate_min_length("username", "alice", 3)
  let r3: ValidationResult = validate_max_length("username", "alice", 20)
  let result: ValidationResult = validation_merge(validation_merge(r1, r2), r3)
  result.valid
}

Capabilities

None. All functions are pure.

Notes / Limitations

• string_length is a runtime built-in; the stub in core.ax returns 0 and is replaced at compile time.
• validate_numeric uses try_parse_int (a pattern-matching built-in); the library does not support float parsing.
• validation_merge returns the first failure only — it does not accumulate multiple errors. If you need to collect all errors, maintain a list of ValidationResult in your app state.

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