Adding CONFIG option (#211)

Signed-off-by: Harsh Mahesheka <[email protected]>

Co-authored-by: Jose Luis Rivero <[email protected]>

cmake/IgnUtils.cmake

@@ -1,7 +1,7 @@
 
 #################################################
 # ign_find_package(<PACKAGE_NAME>
-#                  [REQUIRED] [PRIVATE] [EXACT] [QUIET] [BUILD_ONLY] [PKGCONFIG_IGNORE]
+#                  [REQUIRED] [PRIVATE] [EXACT] [QUIET] [CONFIG] [BUILD_ONLY] [PKGCONFIG_IGNORE]
 #                  [COMPONENTS <components_of_PACKAGE_NAME>]
 #                  [OPTIONAL_COMPONENTS <components_of_PACKAGE_NAME>]
 #                  [REQUIRED_BY <components_of_project>]
@@ -50,6 +50,10 @@
 #          output, except there will be no warning if the package is missing,
 #          unless REQUIRED or REQUIRED_BY is specified.
 #
+# [CONFIG]: Optional. If provided, it will be passed forward to cmake's
+#          find_package(~) command. This will trigger Config mode search rather than
+#          Module mode.
+#
 # [BUILD_ONLY]: Optional. Use this to indicate that the project only needs this
 #               package while building, and it does not need to be available to
 #               the consumer of this project at all. Normally this should only
@@ -138,7 +142,7 @@ macro(ign_find_package PACKAGE_NAME)
 
   #------------------------------------
   # Define the expected arguments
-  set(options REQUIRED PRIVATE EXACT QUIET BUILD_ONLY PKGCONFIG_IGNORE)
+  set(options REQUIRED PRIVATE EXACT QUIET CONFIG BUILD_ONLY PKGCONFIG_IGNORE)
   set(oneValueArgs VERSION PRETTY PURPOSE EXTRA_ARGS PKGCONFIG PKGCONFIG_LIB PKGCONFIG_VER_COMPARISON)
   set(multiValueArgs REQUIRED_BY PRIVATE_FOR COMPONENTS OPTIONAL_COMPONENTS)
 
@@ -162,6 +166,10 @@ macro(ign_find_package PACKAGE_NAME)
     list(APPEND ${PACKAGE_NAME}_find_package_args EXACT)
   endif()
 
+  if(ign_find_package_CONFIG)
+    list(APPEND ${PACKAGE_NAME}_find_package_args CONFIG)
+  endif()
+
   if(ign_find_package_COMPONENTS)
     list(APPEND ${PACKAGE_NAME}_find_package_args COMPONENTS ${ign_find_package_COMPONENTS})
   endif()
@@ -275,6 +283,11 @@ macro(ign_find_package PACKAGE_NAME)
       ign_string_append(${PACKAGE_NAME}_dependency_args EXACT)
     endif()
 
+    # If we have specified to use CONFIG mode, we should provide that as well.
+    if(ign_find_package_CONFIG)
+      ign_string_append(${PACKAGE_NAME}_dependency_args CONFIG)
+    endif()
+
     # NOTE (MXG): 7 seems to be the number of escapes required to get
     # "${ign_package_required}" and "${ign_package_quiet}" to show up correctly
     # as strings in the final config-file outputs. It is unclear to me why the