.. _resolving_issues:

Suggesting New License Detection
================================

Firstly this analysis is then used to suggest new license matches in place of the matches with
different license detection issues, to rectify those issues and provide a better license
detection. This helps in quickly identifying issues when looking at a scan result or in
larger use cases/audits.

This can also help in sub-sequent rule addition in the scancode rules, to enhance the scancode
data.

.. note::

    The rule/.yml file generation/other actions is Work In Progress.
    Only reports with suggested rules with the rule text, license key, rule type is generated.

.. _crafting_rule_text:

Matched Text
------------

When two matched texts having a common boundary and has a common substring, Like in this example:-

- start_line - 16
- end_line - 17
- matched_text::

    * You should have received a copy of the GNU Lesser General Public\n * License along with this library; if not, write to the Free Software

- start_line - 17
- end_line - 19
- matched_text::

    * License along with this library; if not, write to the Free Software\n * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,\n * MA 02110-1301 USA

Here, ``License along with this library; if not, write to the Free Software`` is a substring of both
matched_texts, so we cannot simply join them, we have to join them without this repetition.

If they do have a common boundary but do not have common substrings, then they are joined simply.

Now if they do not have a common boundary,

- Less than or equal to 4 lines gap: They are joined as one Rule
- More than 4 lines gap: They are made two separate rules


.. _predict_license_expression:

Predict License Expression
--------------------------

The steps are as follows:

1. First from the list of `license expressions`, all the `license expressions` are sorted according
   to their occurrences.

2. Generic `license_expressions` like `unknown`, `warranty-disclaimer` are removed fro, this sorted
   list.

3. If there's only one `license_expression` with the most number of occurrences, then that is the
   predicted `license_expression`.

4. In case of same number of `license_expressions` for multiple matches, the `license_expression` of
   the license match with the highest `matched_length` given as the prediction.

.. _crafting_rule_yml:

``.yml`` file attributes
------------------------

1. The boolean value denoting the license type, i.e. license text/notice/tag/reference is determined
   from their respective class of problem, which they are already divided into.

2. The ``ignorable`` attributes are added later by using scripts.

3. The possible license id (like ``mit``) is predicted as the license ID of the match with the
   longest ``match_coverage``. This has to be manually verified in most cases.

4. If the rule is a ``false_positive`` as determined from the class of problem, only the
   ``is_false_positive`` attribute is there.

.. _crafted_rule_confidence:

Rule Confidence
---------------

Calculation of ``rule-confidence`` for manually checking only the low confidence errors.