Add documentation about the 'Check' GPR package

Also correct the description of the 'Switches' attribute.

Do this as the previous commit remove the only example of 'Check' GPR package
usage.

lkql_checker/doc/gnatcheck_rm/using_gnatcheck.rst

@@ -305,6 +305,52 @@ one (non-aggregate) project, the gnatcheck behavior is the same as for the
 case of non-aggregate argument project file.
 
 
+.. _Check_GPR_Package:
+
+The *Check* GPR Package
+=======================
+
+In addition to the command-line options, you can use attributes offered by the
+``Check`` package to configure a GNATcheck run. In order to do this you may add
+the ``Check`` package in the GPR file you're providing to GNATcheck through the
+``-P`` command line options, example given:
+
+.. code-block:: ada
+
+  project My_Project is
+     package Check is
+        ...
+     end Check;
+  end My_Project;
+
+Inside this package you can define the following attributes to configure
+GNATcheck:
+
+* ``Switches``
+  Index is a language name. Value is a list of additional switches to be used
+  when invoking ``gnatcheck``.
+
+  .. attention::
+
+    There are several command-line switches that you cannot pass through the
+    ``Switches`` attribute:
+
+    * ``-P``
+    * ``-U``
+    * ``-Xname=value``
+    * ``-eL``
+    * ``-r, --rule [rule_name]``
+    * ``--rule-file=filename``
+
+    If you're providing one of those switches through the ``Switches`` or the
+    ``Default_Switches`` attribute, GNATcheck will raise an error message and
+    exit with an error code.
+
+* ``Default_Switches``
+  Same as ``Switches``, but provided additional switches will apply only if
+  there is no applicable ``Switches`` attribute.
+
+
 .. _LKQL_options_file:
 
 LKQL Rule Files

lkql_checker/src/gnatcheck-projects.adb

@@ -676,8 +676,7 @@ package body Gnatcheck.Projects is
         (Switches_Attr,
          "Index is a language name. Value is a " &
            "list of switches to be used when invoking 'gnatcheck' for a " &
-           "source of the language, if there is no applicable attribute " &
-           "Switches.");
+           "source of the language.");
       Add_Alias (Name     => Default_Switches_Attr,
                  Alias_Of => Switches_Attr);
       GPR2.Project.Registry.Attribute.Description.Set_Attribute_Description

testsuite/tests/gnatcheck/print_gpr_registry/test.out

@@ -1 +1 @@
-{"packages":[{"attributes":[{"attribute_def":{"builtin":false,"config_concatenable":false,"empty_value":"ALLOW","has_default_in":{"abstract":false,"aggregate":false,"aggregate_library":false,"configuration":false,"library":false,"standard":false},"index_optional":false,"index_type":"LANGUAGE_INDEX","inherit_from_extended":"NOT_INHERITED","is_allowed_in":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true},"is_toolchain_config":false,"value":"LIST","value_case_sensitive":true,"value_is_set":false},"attribute_descr":"Index is a language name. Value is a list of switches to be used when invoking 'gnatcheck' for a source of the language, if there is no applicable attribute Switches.","attribute_name":"Default_Switches"},{"attribute_def":{"builtin":false,"config_concatenable":false,"empty_value":"ALLOW","has_default_in":{"abstract":false,"aggregate":false,"aggregate_library":false,"configuration":false,"library":false,"standard":false},"index_optional":false,"index_type":"LANGUAGE_INDEX","inherit_from_extended":"NOT_INHERITED","is_allowed_in":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true},"is_toolchain_config":false,"value":"LIST","value_case_sensitive":true,"value_is_set":false},"attribute_descr":"Index is a language name. Value is a list of switches to be used when invoking 'gnatcheck' for a source of the language, if there is no applicable attribute Switches.","attribute_name":"Switches"}],"package_descr":"This package specifies the options used when calling the checking tool 'gnatcheck'. Its attribute Default_Switches has the same semantics as for the package Builder. The first string should always be -rules to specify that all the other options belong to the -rules section of the parameters to 'gnatcheck'.","package_name":"Check","projects_kind":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true}},{"attributes":[{"attribute_def":{"builtin":false,"config_concatenable":false,"empty_value":"ALLOW","has_default_in":{"abstract":false,"aggregate":false,"aggregate_library":false,"configuration":false,"library":false,"standard":false},"index_optional":false,"index_type":"NO_INDEX","inherit_from_extended":"NOT_INHERITED","is_allowed_in":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true},"is_toolchain_config":false,"value":"LIST","value_case_sensitive":true,"value_is_set":false},"attribute_descr":"If you want to override ada default file extensions (ada, ads, adb, spc & bdy), use this attribute which includes a list of file patterns where you can specify the following meta characters: * : matches any string of 0 or more characters, ? : matches any character,  [list of chars] : matches any character listed, [char-char] : matches any character in given range, [^list of chars] : matches any character not listed. These patterns are case insensitive.","attribute_name":"File_Patterns"}],"package_descr":"This package specifies the options used when calling the tool 'codepeer'.","package_name":"Codepeer","projects_kind":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true}}]}
+{"packages":[{"attributes":[{"attribute_def":{"builtin":false,"config_concatenable":false,"empty_value":"ALLOW","has_default_in":{"abstract":false,"aggregate":false,"aggregate_library":false,"configuration":false,"library":false,"standard":false},"index_optional":false,"index_type":"LANGUAGE_INDEX","inherit_from_extended":"NOT_INHERITED","is_allowed_in":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true},"is_toolchain_config":false,"value":"LIST","value_case_sensitive":true,"value_is_set":false},"attribute_descr":"Index is a language name. Value is a list of switches to be used when invoking 'gnatcheck' for a source of the language, if there is no applicable attribute Switches.","attribute_name":"Default_Switches"},{"attribute_def":{"builtin":false,"config_concatenable":false,"empty_value":"ALLOW","has_default_in":{"abstract":false,"aggregate":false,"aggregate_library":false,"configuration":false,"library":false,"standard":false},"index_optional":false,"index_type":"LANGUAGE_INDEX","inherit_from_extended":"NOT_INHERITED","is_allowed_in":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true},"is_toolchain_config":false,"value":"LIST","value_case_sensitive":true,"value_is_set":false},"attribute_descr":"Index is a language name. Value is a list of switches to be used when invoking 'gnatcheck' for a source of the language.","attribute_name":"Switches"}],"package_descr":"This package specifies the options used when calling the checking tool 'gnatcheck'. Its attribute Default_Switches has the same semantics as for the package Builder. The first string should always be -rules to specify that all the other options belong to the -rules section of the parameters to 'gnatcheck'.","package_name":"Check","projects_kind":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true}},{"attributes":[{"attribute_def":{"builtin":false,"config_concatenable":false,"empty_value":"ALLOW","has_default_in":{"abstract":false,"aggregate":false,"aggregate_library":false,"configuration":false,"library":false,"standard":false},"index_optional":false,"index_type":"NO_INDEX","inherit_from_extended":"NOT_INHERITED","is_allowed_in":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true},"is_toolchain_config":false,"value":"LIST","value_case_sensitive":true,"value_is_set":false},"attribute_descr":"If you want to override ada default file extensions (ada, ads, adb, spc & bdy), use this attribute which includes a list of file patterns where you can specify the following meta characters: * : matches any string of 0 or more characters, ? : matches any character,  [list of chars] : matches any character listed, [char-char] : matches any character in given range, [^list of chars] : matches any character not listed. These patterns are case insensitive.","attribute_name":"File_Patterns"}],"package_descr":"This package specifies the options used when calling the tool 'codepeer'.","package_name":"Codepeer","projects_kind":{"abstract":true,"aggregate":true,"aggregate_library":true,"configuration":true,"library":true,"standard":true}}]}