cmListCommand: add a policy for failing on invalid indicies

1 files changed, 21 insertions, 0 deletions

diff --git a/Help/policy/CMP0121.rst b/Help/policy/CMP0121.rst
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+CMP0121
+-------
+
+.. versionadded:: 3.21
+
+The :command:`list` command now detects invalid indicies.
+
+Prior to CMake version 3.21, the :command:`list` command's ``GET``,
+``INSERT``, ``SUBLIST``, and ``REMOVE_AT`` subcommands did not detect invalid
+index arguments.
+
+The ``OLD`` behavior of this policy is for invalid indicies to be treated as
+their integer value (if any) at the start of the string. For example,
+``2good4you`` is a ``2`` and ``not_an_integer`` is a ``0``. The ``NEW``
+behavior is for invalid indicies to trigger an error.
+
+This policy was introduced in CMake version 3.21.  CMake version |release|
+warns when the policy is not set and uses ``OLD`` behavior. Use the
+:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
+
+.. include:: DEPRECATED.txt