SCons: Make sure a library gets built before a program - build

Question

I'm trying to port my wayland compositor from make to scons, but I'm having trouble with the build order. I need xdg-shell-protocol to be generated with wayland-scanner and built before anything else. With make, something like this is all it takes:
WLSCAN_INFO = #echo " WLSCAN " $#;
CC_INFO = #echo " CC " $#;
CFLAGS= -g \
-Werror \
-I. \
-DWLR_USE_UNSTABLE
LIBS = "-Lxdg-shell-protocol.h" \
$(shell pkg-config --cflags --libs wlroots) \
$(shell pkg-config --cflags --libs wayland-server) \
$(shell pkg-config --cflags --libs xkbcommon) \
WAYLAND_PROTOCOLS=$(shell pkg-config --variable=pkgdatadir wayland-protocols)
WAYLAND_SCANNER=$(shell pkg-config --variable=wayland_scanner wayland-scanner)
XDG_SHELL_DEPS = xdg-shell-protocol.c xdg-shell-protocol.h
xdg-shell-protocol.h:
$(WLSCAN_INFO)$(WAYLAND_SCANNER) server-header \
$(WAYLAND_PROTOCOLS)/stable/xdg-shell/xdg-shell.xml $#
xdg-shell-protocol.c: xdg-shell-protocol.h
$(WLSCAN_INFO)$(WAYLAND_SCANNER) private-code \
$(WAYLAND_PROTOCOLS)/stable/xdg-shell/xdg-shell.xml $#
OBJS = \
xdg-shell-protocol.o \
output.o \
renderer.o \
input.o \
xdg.o \
cursor.o \
keyboard.o \
main.o
%.o: %.c xdg-shell-protocol.h
$(CC_INFO)$(CC) $(CFLAGS) -c $(LIBS) -o $# $<
wlc: $(OBJS)
$(CC_INFO)$(CC) $(CFLAGS) $(LIBS) -o $# $(OBJS)
clean:
rm -f wlc $(XDG_SHELL_DEPS) *.o
.DEFAULT_GOAL = wlc
.PHONY: wlc clean
With scons, I tried this:
CCFLAGS = "-fdiagnostics-color=always -g -Werror -DWLR_USE_UNSTABLE"
CPPPATH = ["./", "./include"]
env = Environment()
env.Append(CCFLAGS = CCFLAGS)
env.Append(CPPPATH = ["./", "./include"])
env.ParseConfig("pkg-config --cflags --libs wlroots")
env.ParseConfig("pkg-config --cflags --libs wayland-server")
env.ParseConfig("pkg-config --cflags --libs xkbcommon")
env.Command( source = "",
target = "xdg-shell-protocol.h",
action = "`pkg-config --variable=wayland_scanner wayland-scanner` server-header \
`pkg-config --variable=pkgdatadir wayland-protocols`/stable/xdg-shell/xdg-shell.xml \
$TARGET"
)
env.Command( source = "",
target = "xdg-shell-protocol.c",
action = "`pkg-config --variable=wayland_scanner wayland-scanner` private-code \
`pkg-config --variable=pkgdatadir wayland-protocols`/stable/xdg-shell/xdg-shell.xml \
$TARGET"
)
xdg_shell_protocol = env.Library(
target = "xdg-shell-protocol",
source = [
"xdg-shell-protocol.h",
"xdg-shell-protocol.c"
]
)
wlc = env.Program(
target = "wlc",
source = [
Glob("input/*"),
Glob("output/*"),
Glob("shell/*"),
"main.c",
],
LIBS=[xdg_shell_protocol], LIBPATH="."
)
env.Depends(wlc, "xdg-shell-protocol.h")
)
But wlc always gets built before xdg_shell_protocol, and ends up failing because xdg-shell-protocol.h hasn't been generated yet. I also tried:
Defining an explicit dependency by adding env.Depends(wlc, "xdg-shell-protocol.h") or env.Depends(wlc, xdg_shell_protocol) at the end,
Setting LIBS = ["xdg-shell-protocol"] in wlc,
Not using Library and just adding xdg-shell-protocol.h and xdg-shell-protocol.c to the beginning of source in wlc.
But main.c or some other source file always ends up being compiled first and fails because xdg-shell-protocol.h doesn't exist yet.
What am I doing wrong?
EDIT:
Expanded ... above (note that the makefile is from before I moved source files to subdirectories, which was the main reason I decided to change build systems).
Output of $ scons --tree=prune

Answer 1

Please post the full file, the '...''s may be relevant.
Do any of your Command()'s specify the source argument?
What's line 1 of: include/shell/xdg.h ?
try adding this line
env.Depends('input/cursor.c', 'xdg-shell-protocol.h')
NOTE: This is not a good solution, but will help figure out what the issue is.
Now.. Try changing your Program(..) to this, and remove your explicit Depends().
cpppath = env['CPPPATH'] + ['/usr/include']
wlc = env.Program(
target = "wlc",
source = [
Glob("input/*"),
Glob("output/*"),
Glob("shell/*"),
"main.c",
],
LIBS=[xdg_shell_protocol],
CPPPATH=cpppath,
)

Answer 2

The problem is caused by the source scanner not seeing the dependency on xdg-shell-protocol.h because it comes from including /usr/include/wlr/types/wlr_xdg_shell.h, which wouldn't normally be scanned (this was the genesis of the suggestion above to add /usr/include to CPPPATH but that didn't seem to be good enough), and thus you don't get the order you would - forcing that header to get generated early - if it noticed that dependency. From your workaround, I think you can simplify to just this:
env.Depends("include/shell/xdg.h", "xdg-shell-protocol.h")
Which may still end up not being the prettiest answer...

Answer 3

Apparently I have to define the explicit dependency for each source file:
wlc_source = [
"main.c",
Glob("input/*.c"),
Glob("output/*.c"),
Glob("shell/*.c"),
]
for source in wlc_source:
env.Depends(source, xdg_shell_protocol)
wlc = env.Program(
target = "wlc",
source = wlc_source
)
This fixes the issue, but I don't think this is the best solution.