Document limitations of current implementation of PEP 518 in pip
@@ -150,6 +150,8 @@ can be problematic. If this is the case, pip provides a
flag are responsible for ensuring the build environment is managed
appropriately.
+.. _pep-518-limitations:
+
The current implementation of `PEP518`_ in pip requires that any dependencies
specified in ``pyproject.toml`` are available as wheels. This is a technical
limitation of the implementation - dependencies only available as source would
@@ -158,6 +160,10 @@ dependency installation process. The potentially unbounded recursion involved
was not considered acceptable, and so installation of build dependencies from
source has been disabled until a safe resolution of this issue has been found.
+Further, it also doesn't support the use of environment markers and extras,
+only version specifiers are respected. Support for markers and extras will be
+added in a future release.
+
.. _PEP517: http://www.python.org/dev/peps/pep-0517/
.. _PEP518: http://www.python.org/dev/peps/pep-0518/
