ExternalProject: Prevent COMMAND from being treated as a true keyword

The known keywords for each function are obtained by scraping the
documentation for lines matching a particular regular expression. In
commit 8842a027 (ExternalProject: Improve documentation, 2017-07-09),
the docs were overhauled and the COMMAND docs subsequently matched the
regular expression when they shouldn't have. This made COMMAND appear as
a true keyword, which thwarted the special handling logic elsewhere for
the intended use of COMMAND arguments.

This commit contains a workaround for issue #17229 to force a dependency
of the patch step on the update step to ensure a predictable step order.

Fixes: #17198

1 files changed, 8 insertions, 0 deletions

diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
index d92eb5f..912c5ac 100644
--- a/Modules/ExternalProject.cmake
+++ b/Modules/ExternalProject.cmake
@@ -870,6 +870,14 @@ foreach(line IN LISTS lines)
     set(_ep_keyword_sep)
   elseif("${line}" MATCHES "^ +``([A-Z0-9_]+) [^`]*``$")
     set(_ep_key "${CMAKE_MATCH_1}")
+    # COMMAND should never be included as a keyword,
+    # for ExternalProject_Add(), as it is treated as a
+    # special case by argument parsing as an extension
+    # of a previous ..._COMMAND
+    if("x${_ep_key}x" STREQUAL "xCOMMANDx" AND
+       "x${_ep_func}x" STREQUAL "xExternalProject_Addx")
+      continue()
+    endif()
     #message("  keyword [${_ep_key}]")
     string(APPEND _ep_keywords_${_ep_func}
       "${_ep_keyword_sep}${_ep_key}")