Valibot Source Code Documentation

Documentation patterns for library source code in /library/src/.

JSDoc Patterns

Interface Documentation

/**
 * String issue interface.
 */
export interface StringIssue extends BaseIssue<unknown> {
  /**
   * The issue kind.
   */
  readonly kind: 'schema';
  /**
   * The issue type.
   */
  readonly type: 'string';
}

Rules:

• First line: [Name] [category] interface. (e.g., “String issue interface.”)
• Property comments: The [description]. (always start with “The”, end with period)
• All properties use readonly
• No blank lines between property and its comment

Function Overloads

Each overload gets its own complete JSDoc:

/**
 * Creates a string schema.
 *
 * @returns A string schema.
 */
export function string(): StringSchema<undefined>;

/**
 * Creates a string schema.
 *
 * @param message The error message.
 *
 * @returns A string schema.
 */
export function string<
  const TMessage extends ErrorMessage<StringIssue> | undefined,
>(message: TMessage): StringSchema<TMessage>;

Rules:

• First line: Creates a [name] [category]. (use “a” vs “an” correctly)
• Blank line after description
• @param name The [description]. (start with “The”, end with period)
• Blank line after params
• @returns A [name] [category]. or @returns The [description].

Hints

Add hints after the main description, before @param:

/**
 * Creates an object schema.
 *
 * Hint: This schema removes unknown entries. To include unknown entries, use
 * `looseObject`. To reject unknown entries, use `strictObject`.
 *
 * @param entries The entries schema.
 *
 * @returns An object schema.
 */

Links

Link to external resources when relevant using markdown format:

/**
 * Creates an [email](https://en.wikipedia.org/wiki/Email_address) validation action.
 */

Implementation Function

The implementation has NO JSDoc but uses // @__NO_SIDE_EFFECTS__:

// @__NO_SIDE_EFFECTS__
export function string(
  message?: ErrorMessage<StringIssue>
): StringSchema<ErrorMessage<StringIssue> | undefined> {
  return {
    /* ... */
  };
}

// @__NO_SIDE_EFFECTS__ rules:

• Add for pure functions (no external state mutation, no I/O)
• Most schema/action/method factories are pure
• Do NOT add for functions that mutate arguments (like _addIssue)
• Used by bundlers for tree-shaking

Utility Functions

/**
 * Stringifies an unknown input to a literal or type string.
 *
 * @param input The unknown input.
 *
 * @returns A literal or type string.
 *
 * @internal
 */
// @__NO_SIDE_EFFECTS__
export function _stringify(input: unknown): string {
  // ...
}

Rules:

• Use @internal tag for internal utilities
• Prefix internal functions with _
• Only add // @__NO_SIDE_EFFECTS__ if function is pure

Inline Comment Patterns

Section Headers

'~run'(dataset, config) {
  // Get input value from dataset
  const input = dataset.value;

  // If root type is valid, check nested types
  if (Array.isArray(input)) {
    // Set typed to true and value to empty array
    dataset.typed = true;
    dataset.value = [];

    // Parse schema of each array item
    for (let key = 0; key < input.length; key++) {
      // ...
    }
  }
}

Rules:

• Describe WHAT the next code block does
• Present tense verbs: “Get”, “Parse”, “Check”, “Set”, “Add”, “Create”
• Omit articles (“the”, “a”, “an”): “Get input value” not “Get the input value”
• No period at end
• Blank line before comment, no blank line after

Conditional Logic

// If root type is valid, check nested types
if (input && typeof input === 'object') {
  // ...
}

// Otherwise, add issue
else {
  _addIssue(this, 'type', dataset, config);
}

Rules:

• Use “If [condition], [action]”
• Use “Otherwise, [action]” for else branches
• Omit articles

Hint Comments (Exception)

// Hint: The issue is deliberately not constructed with the spread operator
// for performance reasons
const issue: BaseIssue<unknown> = {
  /* ... */
};

Rules:

• Start with “Hint:”
• Explain WHY, not just what
• CAN use articles (unlike other inline comments)
• Document performance decisions, non-obvious logic

TODO Comments

// TODO: Should we add "n" suffix to bigints?
if (type === 'bigint') {
  /* ... */
}

@ts-expect-error

Used for internal dataset mutations TypeScript can’t track:

// @ts-expect-error
dataset.typed = true;

File Type Patterns

Schema Files (string.ts, object.ts, etc.)

1. Issue interface with JSDoc
2. Schema interface with JSDoc
3. Function overloads with full JSDoc each
4. Implementation with // @__NO_SIDE_EFFECTS__
5. Return object with '~run' method containing inline comments

Action Files (email.ts, minLength.ts, etc.)

1. Issue interface (for validation actions)
2. Action interface with JSDoc
3. Function overloads with JSDoc
4. Implementation with // @__NO_SIDE_EFFECTS__

Method Files (parse.ts, pipe.ts, etc.)

More complex logic, require more inline comments.

Utility Files (_addIssue.ts, _stringify.ts)

1. Single function with JSDoc including @internal
2. // @__NO_SIDE_EFFECTS__ only if pure

Terminology Consistency

JSDoc descriptions must match the kind property if present:

Quick Reference

JSDoc First Lines

Inline Comment Starters

Terminology

Use consistently:

• Schema (not “validator”)
• Action (not “validation” for the object)
• Issue (not “error” in type names)
• Dataset (internal data structure)
• Config/Configuration (not “options”)

Checklist

• Interfaces: [Name] [category] interface.
• Properties: The [description].
• Overloads: Complete JSDoc each
• Implementation: NO JSDoc
• Pure functions: // @__NO_SIDE_EFFECTS__
• Impure functions (mutate args): NO @__NO_SIDE_EFFECTS__
• Internal utilities: @internal tag
• Inline comments: No articles (except Hint), no periods
• JSDoc comments: End with periods