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template-no-duplicate-form-names.md

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ember/template-no-duplicate-form-names

This rule disallows two form controls sharing the same name attribute within the same <form> (or within the template root, if no <form> wraps the controls).

Duplicate names break form serialization: both values are emitted into the entry list, and server-side code that expects a single value typically reads only one — often not the one the author intended.

Three categories are exempt from the duplicate check:

  • Non-submitting controls (<input type="button">, <input type="reset">, <button type="button">, <button type="reset">) are skipped entirely. Per HTML §4.10.21.4 they do not contribute to the form data, so their name can't collide with anything.
  • Radio groups (<input type="radio">) share a name with same-type siblings to express mutual exclusion — exactly one contributes per submission.
  • Submit-like controls may share a name across any mix of <input type="submit">, <input type="image">, and <button> (bare <button> defaults to type="submit" per HTML §4.10.9). Only one submit-like control contributes to the form-data entry list per submission — the one the user activated — so same-name is unambiguous.

Examples

This rule forbids the following:

<form>
  <input name='email' />
  <input name='email' />
</form>

<form>
  <input type='text' name='field' />
  <textarea name='field'></textarea>
</form>

This rule allows the following:

<form>
  <input type='radio' name='color' value='red' />
  <input type='radio' name='color' value='blue' />
  <input type='submit' name='action' value='save' />
  <input type='submit' name='action' value='publish' />
</form>

Controls with the HTML disabled attribute are ignored — per HTML §4.10.21.4 they do not contribute to the form-data entry list and cannot collide.

Controls with the HTML hidden attribute are not exempt: hidden affects rendering, not form submission. A hidden control still submits its name/value, so a duplicate name involving a hidden control is a real collision.

Limitations

  • Controls associated with a form via the form="id" attribute (rather than by nesting inside a <form> element) are not tracked by this rule. Only controls that are descendants of a <form> element are scoped to that form.
  • name values via mustache (name={{this.fieldName}}) are skipped — we cannot know the value at lint time.
  • The name[] PHP-style array pattern is treated as an ordinary name; if you declare two name="x[]" controls in the same form this rule will still flag them. Support for array brackets may be added later.
  • The <input type="hidden"> + <input type="checkbox"> default-value pattern (which is permitted in HTML) is not recognized — the pair will be flagged if you use it. Rename the hidden input if you hit this.

References