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How to contribute
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Error Reports
==============================

Please report any issue to the `GitHub Issue Tracker <https://github.com/prestodb/sql/issues>`_:

   1) Provide the **Sample SQL** (shortened and simplified, properly formatted)
   2) State the exact **Version of the Presto SQL:2016 Parser**
   3) State the **RDBMS** in use and point on the applicable Grammar specification
   4) Please write in **English** and post **Plain Text only** (avoiding screen shots or bitmap pictures).

Feature Requests
==============================

**Presto SQL:2016 Parser** is a demand-driven software library, where many contributors have shared solutions for their own needs. Requests for new features have a good chance to get implemented when

   1) the request is about a commonly used feature for one of the major RDBMS
   2) or the request is backed by a sponsor or a bounty, which may attract developers to spend their time on it.

Implementing new Features
==============================

The team around **Presto SQL:2016 Parser** warmly welcomes Code Contributions and Pull Requests. Please follow the guidance below and do not hesitate to ask us for assistance.

Create a new Git Branch
------------------------------

When starting afresh, clone the **Presto SQL:2016 Parser** from the `GitHub` repository:

.. code-block:: Bash

   git clone https://github.com/prestodb/sql.git
   cd sql
   git branch <new-branch>

When having a local repository already, then pull/merge from the `GitHub` repository:

.. code-block:: Bash

   cd sql
   git pull origin master
   git branch <new-branch>

Amend the Code
------------------------------

The **Presto SQL:2016 Parser** is generated by ``JavaCC`` based on the provided Grammar. The Grammar defines how a SQL Text is read and translated into Java Objects. Thus any contribution will depend on the following steps:

   1) Edit the ``JavaCC`` Grammar at ``sql/parser/grammar``
   2) Add or edit the Java Classes at ``sql/parser/src/main/java/com/facebook/coresql/parser/`` to facilitate this Grammar.
   3) Provide Java Unit Tests at ``sql/parser/src/test/java/com/facebook/coresql/parser/`` to test the new feature

      * The test should call the method ``TestUtils.assertParseAndUnparse()`` at least one time 
      * The test should ensure complete coverage of the new Java Classes.
      * The complete test suite must succeed.

   4) Add the description of the new feature to the ``README.md`` file, section `Extensions`.
   5) Build the package with ``Maven`` and ensure, all checks do pass (PMD and CheckStyle and Code Formatting).

Manage Reserved Keywords
------------------------------

Since **Presto SQL:2016 Parser** is built by JavaCC from a Token based Grammar, ``Reserved Keywords`` need a special treatment. All Tokens of the Grammar would become ``Reserved Keywords`` -- unless explicitly allowed.

.. code-block:: sql
    :caption: Allow Keyword example

    -- <OVERLAPS:"OVERLAPS"> is a Token, recently defined in the Grammar
    -- Although it is not restricted by the SQL Standard and could be used for Column, Table and Alias names
    -- Explicitly allowing OVERLAPS by adding it to the  NonReservedKeywords() Production will allow for parsing the following statement

    SELECT Overlaps( overlaps ) AS overlaps
    FROM overlaps.overlaps overlaps
    WHERE overlaps = 'overlaps'
        AND (CURRENT_TIME, INTERVAL '1' HOUR) OVERLAPS (CURRENT_TIME, INTERVAL -'1' HOUR)
    ;

So we will need to define and allow any Keywords which may be allowed for Object Names (such as `Schema`, `Table`, `Column`, `Function`, `Alias`). This White-List must be updated whenever the Tokens of the Grammar change (e. |_| g. when adding a new Token or Production).
Otherwise any new Token or Production will become a ``Reserved Keyword`` automatically and can't be used for Object Names without quoting.


Commit a Pull Request
---------------------------------

.. code-block:: Bash

   cd sql
   git add -A
   git commit -m <title> -m <description>
   git push –set-upstream origin <new-branch>

Follow the advice on `Meaningful Commit Messages <https://www.freecodecamp.org/news/how-to-write-better-git-commit-messages/>`_ and consider using `Commitizen <https://commitizen-tools.github.io/commitizen/>`_ when describing your commits.

Please consider using `Conventional Commits` and structure your commit message as follows:

.. code-block:: text
    :caption: Conventional Commit Message Structure

    <type>[optional scope]: <description>

    [optional body]

    [BREAKING CHANGE: <change_description>]

    [optional footer(s)]

.. list-table:: Commit Message Types
   :widths: 15 85
   :header-rows: 1

   * - Type
     - Description
   * - **feat**
     - introduce a new feature
   * - **fix**
     - patches a bug in your codebase (bugfix or hotfix)
   * - **build**
     - changes that affect the build system or external dependencies
   * - **chore**
     - updates dependencies and does not relate to fix or feat and does not modify src or test files.
   * - **ci**
     - changes that affect the continuous integration process
   * - **docs**
     - updates the documentation or introduce documentation
   * - **style**
     - updates the formatting of code; remove white spaces, add missing spaces, remove unnecessary newlines
   * - **refactor**
     - reactors code segments to optimize readability without changing behavior
   * - **perf**
     - improve performance
   * - **test**
     - add/remove/update tests
   * - **revert**
     - reverts one or many previous commits

Please visit `Better Programming <https://betterprogramming.pub/write-better-git-commit-messages-to-increase-your-productivity-89fa773e8375>`_ for more information and guidance.