Form Autofill Heuristics
========================

Form Autofill Heuristics module is for detecting the field type based on `autocomplete attribute <https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#autofill>`_, `the regular expressions <https://searchfox.org/mozilla-central/source/toolkit/components/formautofill/shared/HeuristicsRegExp.sys.mjs>`_ and the customized logic in each parser.

Debugging
---------

The pref ``extensions.formautofill.heuristics.enabled`` is "true" in default. Set it to "false" could be useful to verify the result of autocomplete attribute.

Dependent APIs
--------------

``element.getAutocompleteInfo()`` provides the parsed result of ``autocomplete`` attribute which includes the field name and section information defined in `autofill spec <https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#autofill>`_

Regular Expressions
-------------------

This section is about how the regular expression is applied during parsing fields. All regular expressions are in `HeuristicsRegexp.sys.mjs <https://searchfox.org/mozilla-central/source/toolkit/components/formautofill/shared/HeuristicsRegExp.sys.mjs>`_.

Parser Implementations
----------------------

The parsers are for detecting the field type more accurately based on the near context of a field. Each parser uses ``FieldScanner`` to traverse the interested fields with the result from the regular expressions and adjust each field type when it matches to a grammar.

* _parsePhoneFields

  * related type: ``tel``, ``tel-*``

* _parseStreetAddressFields

  * related type: ``street-address`, `address-line[1-3]``

* _parseAddressFields

  * related type: ``address-level[1-2]``

* _parseCreditCardExpiryFields

  * related type: ``cc-exp``, ``cc-exp-month``, ``cc-exp-year``

* _parseCreditCardNameFields

  * related type: ``cc-name``, ``given-name``, ``additional-name``, ``family-name``

* _parseCreditCardNumberFields

  * related type: ``cc-number``