Help: Clarify behavior of INHERITED properties

Fixes: #17839

Help/command/define_property.rst

@@ -34,10 +34,24 @@ actual scope needs to be given; only the kind of scope is important.
 The required ``PROPERTY`` option is immediately followed by the name of
 the property being defined.
 
-If the ``INHERITED`` option then the :command:`get_property` command will
+If the ``INHERITED`` option is given, then the :command:`get_property` command
-chain up to the next higher scope when the requested property is not set
+will chain up to the next higher scope when the requested property is not set
-in the scope given to the command. ``DIRECTORY`` scope chains to
+in the scope given to the command.
-``GLOBAL``. ``TARGET``, ``SOURCE``, and ``TEST`` chain to ``DIRECTORY``.
+
+* ``DIRECTORY`` scope chains to its parent directory's scope, continuing the
+  walk up parent directories until a directory has the property set or there
+  are no more parents.  If still not found at the top level directory, it
+  chains to the ``GLOBAL`` scope.
+* ``TARGET``, ``SOURCE`` and ``TEST`` properties chain to ``DIRECTORY`` scope,
+  including further chaining up the directories, etc. as needed.
+
+Note that this scope chaining behavior only applies to calls to
+:command:`get_property`, :command:`get_directory_property`,
+:command:`get_target_property`, :command:`get_source_file_property` and
+:command:`get_test_property`.  There is no inheriting behavior when *setting*
+properties, so using ``APPEND`` or ``APPEND_STRING`` with the
+:command:`set_property` command will not consider inherited values when working
+out the contents to append to.
 
 The ``BRIEF_DOCS`` and ``FULL_DOCS`` options are followed by strings to be
 associated with the property as its brief and full documentation.

Help/command/get_directory_property.rst

@@ -7,11 +7,16 @@ Get a property of ``DIRECTORY`` scope.
 
   get_directory_property(<variable> [DIRECTORY <dir>] <prop-name>)
 
-Store a property of directory scope in the named variable.  If the
+Store a property of directory scope in the named ``<variable>``.
-property is not defined the empty-string is returned.  The ``DIRECTORY``
+The ``DIRECTORY`` argument specifies another directory from which
-argument specifies another directory from which to retrieve the
+to retrieve the property value instead of the current directory.
-property value.  The specified directory must have already been
+The specified directory must have already been traversed by CMake.
-traversed by CMake.
+
+If the property is not defined for the nominated directory scope,
+an empty string is returned.  In the case of ``INHERITED`` properties,
+if the property is not found for the nominated directory scope,
+the search will chain to a parent scope as described for the
+:command:`define_property` command.
 
 ::
 

Help/command/get_property.rst

@@ -50,7 +50,10 @@ be one of the following:
 
 The required ``PROPERTY`` option is immediately followed by the name of
 the property to get.  If the property is not set an empty value is
-returned.  If the ``SET`` option is given the variable is set to a boolean
+returned, although some properties support inheriting from a parent scope
+if defined to behave that way (see :command:`define_property`).
+
+If the ``SET`` option is given the variable is set to a boolean
 value indicating whether the property has been set.  If the ``DEFINED``
 option is given the variable is set to a boolean value indicating
 whether the property has been defined such as with the

Help/command/get_source_file_property.rst

@@ -8,9 +8,15 @@ Get a property for a source file.
   get_source_file_property(VAR file property)
 
 Get a property from a source file.  The value of the property is
-stored in the variable ``VAR``.  If the property is not found, ``VAR``
+stored in the variable ``VAR``.  If the source property is not found, the
-will be set to "NOTFOUND".  Use :command:`set_source_files_properties`
+behavior depends on whether it has been defined to be an ``INHERITED`` property
-to set property values.  Source file properties usually control how the
+or not (see :command:`define_property`).  Non-inherited properties will set
-file is built. One property that is always there is :prop_sf:`LOCATION`
+``VAR`` to "NOTFOUND", whereas inheritied properties will search the relevent
+parent scope as described for the :command:`define_property` command and
+if still unable to find the property, ``VAR`` will be set to an empty string.
+
+Use :command:`set_source_files_properties` to set property values.  Source
+file properties usually control how the file is built. One property that is
+always there is :prop_sf:`LOCATION`.
 
 See also the more general :command:`get_property` command.

Help/command/get_target_property.rst

@@ -8,8 +8,15 @@ Get a property from a target.
   get_target_property(VAR target property)
 
 Get a property from a target.  The value of the property is stored in
-the variable ``VAR``.  If the property is not found, ``VAR`` will be set to
+the variable ``VAR``.  If the target property is not found, the behavior
-"NOTFOUND".  Use :command:`set_target_properties` to set property values.
+depends on whether it has been defined to be an ``INHERITED`` property
+or not (see :command:`define_property`).  Non-inherited properties will
+set ``VAR`` to "NOTFOUND", whereas inheritied properties will search the
+relevent parent scope as described for the :command:`define_property`
+command and if still unable to find the property, ``VAR`` will be set to
+an empty string.
+
+Use :command:`set_target_properties` to set target property values.
 Properties are usually used to control how a target is built, but some
 query the target instead.  This command can get properties for any
 target so far created.  The targets do not need to be in the current

Help/command/get_test_property.rst

@@ -8,8 +8,14 @@ Get a property of the test.
   get_test_property(test property VAR)
 
 Get a property from the test.  The value of the property is stored in
-the variable ``VAR``.  If the test or property is not found, ``VAR`` will
+the variable ``VAR``.  If the test property is not found, the behavior
-be set to "NOTFOUND".  For a list of standard properties you can type
+depends on whether it has been defined to be an ``INHERITED`` property
-``cmake --help-property-list``.
+or not (see :command:`define_property`).  Non-inherited properties will
+set ``VAR`` to "NOTFOUND", whereas inheritied properties will search the
+relevent parent scope as described for the :command:`define_property`
+command and if still unable to find the property, ``VAR`` will be set to
+an empty string.
+
+For a list of standard properties you can type ``cmake --help-property-list``.
 
 See also the more general :command:`get_property` command.

Help/command/set_property.rst

@@ -59,11 +59,17 @@ be one of the following:
 
 The required ``PROPERTY`` option is immediately followed by the name of
 the property to set.  Remaining arguments are used to compose the
-property value in the form of a semicolon-separated list.  If the
+property value in the form of a semicolon-separated list.
-``APPEND`` option is given the list is appended to any existing property
+
-value.  If the ``APPEND_STRING`` option is given the string is append to any
+If the ``APPEND`` option is given the list is appended to any existing
-existing property value as string, i.e.  it results in a longer string
+property value.  If the ``APPEND_STRING`` option is given the string is
-and not a list of strings.
+appended to any existing property value as string, i.e. it results in a
+longer string and not a list of strings.  When using ``APPEND`` or
+``APPEND_STRING`` with a property defined to support ``INHERITED``
+behavior (see :command:`define_property`), no inheriting occurs when
+finding the initial value to append to.  If the property is not already
+directly set in the nominated scope, the command will behave as though
+``APPEND`` or ``APPEND_STRING`` had not been given.
 
 See the :manual:`cmake-properties(7)` manual for a list of properties
 in each scope.