From deb080bd4f0d8a1b32c0a1af430f18046ca8e517 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Konstantin=20=C4=90or=C4=91evi=C4=87?=
 <vomindoraan@gmail.com>
Date: Wed, 13 May 2020 02:48:45 +0200
Subject: [PATCH] Demo <FEATURE>_SUPPORTED flags working with post_keymap

---
 build_keyboard.mk                    |  7 ++++---
 keyboards/maartenwut/wasdat/rules.mk |  1 +
 users/konstantin/my_backlight.c      |  1 +
 users/konstantin/post_keymap.mk      | 11 +++++++++++
 users/konstantin/rules.mk            |  2 +-
 5 files changed, 18 insertions(+), 4 deletions(-)
 create mode 100644 users/konstantin/my_backlight.c

diff --git a/build_keyboard.mk b/build_keyboard.mk
index 5252499efb85..d9ab05649b2c 100644
--- a/build_keyboard.mk
+++ b/build_keyboard.mk
@@ -286,6 +286,10 @@ ifneq ("$(wildcard $(KEYBOARD_PATH_5)/post_config.h)","")
     POST_CONFIG_H += $(KEYBOARD_PATH_5)/post_config.h
 endif
 
+# Disable features that a keyboard doesn't support
+# Process after keyboard, userspace and keymap, but before post_keymap
+-include disable_features.mk
+
 # Userspace makefile second pass
 -include $(USER_PATH)/post_keymap.mk
 # Userspace config.h first pass
@@ -293,9 +297,6 @@ ifneq ("$(wildcard $(USER_PATH)/config.h)","")
     CONFIG_H += $(USER_PATH)/config.h
 endif
 
-# Disable features that a keyboard doesn't support
--include disable_features.mk
-
 # Object files directory
 #     To put object files in current directory, use a dot (.), do NOT make
 #     this an empty or blank macro!
diff --git a/keyboards/maartenwut/wasdat/rules.mk b/keyboards/maartenwut/wasdat/rules.mk
index 822baf5ed845..850ca2403379 100644
--- a/keyboards/maartenwut/wasdat/rules.mk
+++ b/keyboards/maartenwut/wasdat/rules.mk
@@ -24,6 +24,7 @@ SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
 # if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
 NKRO_ENABLE = yes           # USB Nkey Rollover
 BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
+BACKLIGHT_SUPPORTED = no
 RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
 MIDI_ENABLE = no            # MIDI support
 BLUETOOTH_ENABLE = no       # Enable Bluetooth with the Adafruit EZ-Key HID
diff --git a/users/konstantin/my_backlight.c b/users/konstantin/my_backlight.c
new file mode 100644
index 000000000000..032d6b2ebdcb
--- /dev/null
+++ b/users/konstantin/my_backlight.c
@@ -0,0 +1 @@
+This will error out if it gets included in the build.
diff --git a/users/konstantin/post_keymap.mk b/users/konstantin/post_keymap.mk
index a762a3699af4..e88d50500017 100644
--- a/users/konstantin/post_keymap.mk
+++ b/users/konstantin/post_keymap.mk
@@ -12,3 +12,14 @@ endif
 ifneq (,$(filter yes,$(UNICODE_ENABLE) $(UNICODEMAP_ENABLE)))
     SRC += unicode.c
 endif
+# Context: The user konstantin has `BACKLIGHT_ENABLE = yes` in their userspace,
+# and is trying to build `make maartenwut/wasdat:konstantin`, a keyboard that
+# has `BACKLIGHT_SUPPORTED = no` declared.
+# If everything works correctly, at this point in the build (post_keymap.mk),
+# the supported flag will have overridden the enable flag and set it to no, so
+# the .c file will NOT be included and the build will finish successfully.
+# The keyboard's "backlight not supported" flag is respected by default,
+# without requiring extra checks in the makefile.
+ifeq ($(strip $(BACKLIGHT_ENABLE)), yes)
+    SRC += my_backlight.c
+endif
diff --git a/users/konstantin/rules.mk b/users/konstantin/rules.mk
index 475e930861d8..d43a9702f07b 100644
--- a/users/konstantin/rules.mk
+++ b/users/konstantin/rules.mk
@@ -9,7 +9,7 @@ TAP_DANCE_ENABLE   = yes
 UNICODEMAP_ENABLE  = yes
 
 # Keyboard-specific feature defaults
-BACKLIGHT_ENABLE   = no
+BACKLIGHT_ENABLE   = yes  # Enabled in userspace, but keyboard has BACKLIGHT_SUPPORTED = no
 RGBLIGHT_ENABLE    = no
 RGB_MATRIX_ENABLE  = no