Help: Document the $CACHE{} syntax

Also add a test case for the behavior.

1 files changed, 17 insertions, 0 deletions

diff --git a/Help/variable/CACHE.rst b/Help/variable/CACHE.rst
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+CACHE
+-----
+
+Read cache variables.
+
+Use the syntax ``$CACHE{VAR}`` to read cache entry ``VAR``.
+See the :ref:`cmake-language(7) variables <CMake Language Variables>`
+documentation for more complete documentation of the interaction of
+normal variables and cache entries.
+
+When evaluating :ref:`Variable References` of the form ``${VAR}``,
+CMake first searches for a normal variable with that name, and if not
+found CMake will search for a cache entry with that name.
+The ``$CACHE{VAR}`` syntax can be used to do direct cache lookup and
+ignore any existing normal variable.
+
+See the :command:`set` command to see how to write cache variables.