Default genhtml opts to LCOV_OPTS; respect explicitly empty HTML_OPTS

Author: tevio

cmake/script/CoverageInclude.cmake.in

@@ -26,10 +26,17 @@ set(LCOV_COMMAND ${LCOV_EXECUTABLE} --gcov-tool ${CMAKE_CURRENT_LIST_DIR}/cov_to
 find_program(GENHTML_EXECUTABLE genhtml REQUIRED)
 
 # HTML_OPTS is optionally passed via -D flag.
-# If HTML_OPTS is not provided, implicitly pass LCOV_OPTS to genhtml.
+# If HTML_OPTS is not provided at all, implicitly pass LCOV_OPTS to genhtml.
+# If HTML_OPTS is provided but empty (e.g. -DHTML_OPTS=""), use an empty list
+# and do NOT inherit LCOV_OPTS.
+set(_HTML_OPTS_WAS_DEFINED FALSE)
+if(DEFINED HTML_OPTS)
+  set(_HTML_OPTS_WAS_DEFINED TRUE)
+endif()
 separate_arguments(HTML_OPTS)
-set(GENHTML_OPTS ${HTML_OPTS})
-if(NOT GENHTML_OPTS)
+if(_HTML_OPTS_WAS_DEFINED)
+  set(GENHTML_OPTS ${HTML_OPTS})
+else()
   set(GENHTML_OPTS ${LCOV_OPTS})
 endif()
 set(GENHTML_COMMAND ${GENHTML_EXECUTABLE} --show-details ${GENHTML_OPTS})

doc/developer-notes.md

@@ -508,10 +508,15 @@ enabled by setting `LCOV_OPTS="--rc branch_coverage=1"`:
 cmake -DLCOV_OPTS="--rc branch_coverage=1" -P build/Coverage.cmake
 ```
 
-HTML_OPTS can override the genhtml options (which default to LCOV_OPTS).
+HTML_OPTS can override the genhtml options (which default to LCOV_OPTS). If HTML_OPTS is omitted, LCOV_OPTS are implicitly passed to genhtml. If HTML_OPTS is provided but empty (e.g. -DHTML_OPTS=""), no options are passed to genhtml and LCOV_OPTS are not inherited.
 
+Examples:
 ```
-cmake -DHTML_OPTS="--exclude boost" -P build/Coverage.cmake
+# Override genhtml options explicitly
+cmake -DHTML_OPTS="--title 'Knots Coverage'" -P build/Coverage.cmake
+
+# Provide an empty override: pass nothing to genhtml (do not inherit LCOV_OPTS)
+cmake -DHTML_OPTS="" -P build/Coverage.cmake
 ```
 
 To enable test parallelism: