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Is email strict

isEmailStrict validates that a value is a strict RFC‑style email address.

It enforces a detailed pattern for both the local part and domain, rejecting malformed, ambiguous, or loosely formatted email strings. Any non‑string value or string that fails the strict pattern results in a single validation event. Otherwise, it produces no validation output.

Signature

Through the API:

.isEmailStrict();

And internally:

export const isEmailStrict: ValidationRule
(value: unknown, path: FieldPath) => Promise<ReadonlyArray<JaneEvent>>

Events

Event code Description
type.not.valid Value is not a string.
string.not.strict-email String does not match the strict RFC‑style pattern.

Design rationale

  • Enforces a stricter pattern than general‑purpose email validators.
  • Rejects non‑string values early with a structural‑type diagnostic.
  • Ensures both local part and domain follow RFC‑style constraints.
  • Avoids normalization — contributors must provide canonical email strings.
  • Emits exactly one event per failure for clarity and composability.
  • Pure, total, async‑compatible, and returns a readonly array of JaneEvent objects.
  • Preserves the provided path and supports pipeline‑level userMessage overrides.

Invoke

isEmailStrict runs only when explicitly included in a boundary or pipeline. It does not run automatically.

The rule activates when:

  • The value is any JavaScript value.
  • If the value is not a string, emits type.not.valid.
  • If the string does not match the strict regex: /^[a-zA-Z0-9.!#$%&'*+/=?^_{|}~-]+@[a-zA-Z0-9-]+(?:.[a-zA-Z0-9-]+)+$/, → emits string.not.strict-email.
  • Otherwise, returns an empty result set.

Examples

Valid — strict RFC‑style email addresses

await isEmailStrict("user@example.com", "$");
// → []

await isEmailStrict("john.doe+tag@sub.domain.org", "$");
// → []

Invalid — non‑string values

await isEmailStrict(123, "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "type.not.valid",
//       path: "$",
//       ...
//     }
//   ]

Invalid — incorrect format

await isEmailStrict("user@", "$");
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.strict-email",
//       path: "$",
//       ...
//     }
//   ]

await isEmailStrict("user@domain", "$"); // missing TLD
// → [
//     JaneEvent{
//       kind: "error",
//       code: "string.not.strict-email",
//       path: "$",
//       ...
//     }
//   ]