docs: add user guide

Author: kenjis

user_guide_src/source/changelogs/v4.3.0.rst

@@ -23,6 +23,20 @@ Exceptions when Database Errors Occur
 - The exceptions thrown by the database connection classes have been changed to ``CodeIgniter\Database\Exceptions\DatabaseException``. Previously, different database drivers threw different exception classes, but these have been unified into ``DatabaseException``.
 - The exceptions thrown by the ``execute()`` method of Prepared Queries have been changed to ``DatabaseException``. Previously, different database drivers might throw different exception classes or did not throw exceptions, but these have been unified into ``DatabaseException``.
 
+HTTP Status Code and Exit Code when Exception Occurs
+----------------------------------------------------
+
+Previously, the CodeIgniter's Exception Handler used the *Exception code* as *HTTP status code* in some cases, and set calculated *Exit code* based on the Exception code. However there is essentially nothing to do with Exception code and HTTP Status Code or Exit code.
+
+- Now the Exception Handler sets HTTP status code to ``500`` and set Exit code to the constant ``EXIT_ERROR`` (= ``1``) by default.
+- You can change HTTP status code or Exit code to implements ``HTTPExceptionInterface`` or ``HasExitCodeInterface`` in your Exception class.
+
+For example, the Exit code has been changed like the following:
+
+- If an uncaught ``ConfigException`` occurs, the Exit code is ``EXIT_CONFIG`` (= ``3``) instead of ``12``.
+- If an uncaught ``CastException`` occurs, the Exit code is ``EXIT_CONFIG`` (= ``3``) instead of ``9``.
+- If an uncaught ``DatabaseException`` occurs, the Exit code is ``EXIT_DATABASE`` (= ``8``) instead of ``17``.
+
 Others
 ------
 

user_guide_src/source/general/errors.rst

@@ -64,10 +64,10 @@ To ignore logging on other status codes, you can set the status code to ignore i
 .. note:: It is possible that logging still will not happen for exceptions if your current Log settings
     are not set up to log **critical** errors, which all exceptions are logged as.
 
-Custom Exceptions
-=================
+Framework Exceptions
+====================
 
-The following custom exceptions are available:
+The following framework exceptions are available:
 
 PageNotFoundException
 ---------------------
@@ -89,7 +89,7 @@ is not the right type, etc:
 
 .. literalinclude:: errors/008.php
 
-This provides an HTTP status code of 500 and an exit code of 3.
+This provides an exit code of 3.
 
 DatabaseException
 -----------------
@@ -99,7 +99,7 @@ or when it is temporarily lost:
 
 .. literalinclude:: errors/009.php
 
-This provides an HTTP status code of 500 and an exit code of 8.
+This provides an exit code of 8.
 
 RedirectException
 -----------------
@@ -113,3 +113,23 @@ forcing a redirect to a specific route or URL:
 redirect code to use instead of the default (``302``, "temporary redirect"):
 
 .. literalinclude:: errors/011.php
+
+.. _error-specify-http-status-code:
+
+Specify HTTP Status Code in Your Exception
+==========================================
+
+Since v4.3.0, you can specify the HTTP status code for your Exception class to implement
+``HTTPExceptionInterface``.
+
+When an exception implemented ``HTTPExceptionInterface`` is caught by CodeIgniter's exception handler, the Exception code will be the HTTP status code.
+
+.. _error-specify-exit-code:
+
+Specify Exit Code in Your Exception
+===================================
+
+Since v4.3.0, you can specify the exit code for your Exception class to implement
+``HasExitCodeInterface``.
+
+When an exception implemented ``HasExitCodeInterface`` is caught by CodeIgniter's exception handler, the code returned from the ``getExitCode()`` method will be the exit code.

user_guide_src/source/installation/upgrade_430.rst

@@ -44,6 +44,17 @@ Add **types** to the properties in these Config classes. You may need to fix the
 Breaking Changes
 ****************
 
+HTTP Status Code and Exit Code of Uncaught Exceptions
+=====================================================
+
+- If you expect *Exception code* as *HTTP status code*, the HTTP status code will be changed.
+  In that case, you need to implements ``HTTPExceptionInterface`` in the Exception. See :ref:`error-specify-http-status-code`.
+- If you expect *Exit code* based on *Exception code*, the Exit code will be changed.
+  In that case, you need to implements ``HasExitCodeInterface`` in the Exception. See :ref:`error-specify-exit-code`.
+
+Others
+======
+
 - The exception classes may be changed when database errors occur. If you catch the exceptions, you must confirm that your code can catch the exceptions. See :ref:`exceptions-when-database-errors-occur` for details.
 
 Breaking Enhancements