PIO: enabled -Wextra for _my_ code

and not for dependencies

config/common.ini

@@ -21,11 +21,6 @@ build_flags =
 
     ; todo: enable more code quality checkers, just exclude vendor libs somehow…
 
-    ; This enables some extra warning flags that are not enabled by -Wall.
-    ; https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
-    ; it is OK for my code, shitload of warnings for included libs
-;    -Wextra
-
     ; Warn when a function declaration hides virtual functions from a base clas
     ; https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html
     ; it is OK for my code, shitload of warnings for included libs
@@ -58,3 +53,27 @@ build_flags =
     ; https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html
     ; Too much shit from included libs
 ;    -fanalyzer
+
+; List of flags that I want to be applied to _my_ code,
+; while I don't want them for the external libraries (dependencies).
+;
+; Despite the name, it applies also to files in `lib` and `test`.
+;
+; -> Mostly because the external libs are not / will not be fixed,
+;    and I don't want them to pollute my build results.
+; -> Hence not using `build_flags`.
+;
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_src_flags.html
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_flags.html
+build_src_flags =
+    ; Enables some extra warning flags that are not enabled by -Wall.
+    ; https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html
+    ;
+    ; todo: check that unity warning disappears after PIO upgrade to 6.1.7:
+    ;       .pio/build/native/unity_config/unity_config.c:39:37:
+    ;       warning: unused parameter 'baudrate' [-Wunused-parameter]
+    ;       https://github.com/platformio/platformio-core/pull/4610
+    ;
+    ; todo: move to build_flags when fixed:
+    ;       https://github.com/ayushsharma82/WebSerial/pull/63
+    -Wextra

config/native.ini

@@ -26,6 +26,11 @@ lib_compat_mode = off
 build_flags =
     ${common.build_flags}
 
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_src_flags.html
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_flags.html
+build_src_flags =
+    ${common.build_src_flags}
+
 ; https://docs.platformio.org/en/latest/projectconf/section_env_build.html#build-src-filter
 build_src_filter = "+<native.cpp>"
 

config/nodemcu.ini

@@ -87,6 +87,11 @@ build_flags =
     ; https://git-scm.com/docs/pretty-formats/2.39.0
     !echo '-D BUILD_GIT_COMMIT_HASH=\\"'$(git log -1 --format=%%h)'\\"'
 
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_src_flags.html
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/build/build_flags.html
+build_src_flags =
+    ${common.build_src_flags}
+
 ; https://docs.platformio.org/en/latest/projectconf/section_env_library.html#lib-deps
 lib_deps =
     ${common.lib_deps}