SConstruct : Added INCLUDE_PATHS option and skip empty include paths

INCLUDE_PATHS is a list argument that can be used to add an arbitrary
list of include paths to be added, with full control over their order
from the options file.

We are also avoiding adding any include paths that are empty, when using
the old arguments.

That is not strictly necessary (we could be setting it to an invalid
path, for example) but does result in a much cleaner compile command.

Author: ivanimanishi

Changes

@@ -1,6 +1,12 @@
 10.6.x.x (relative to 10.6.2.0)
 ========
 
+Build
+-----
+
+- SConstruct :
+  - Added `INCLUDE_PATHS` option.
+  - Empty include path options are no longer added to the compile commands.
 
 
 10.6.2.0 (relative to 10.6.1.0)

SConstruct

@@ -647,6 +647,11 @@ o.Add(
 	BoolVariable( "INSTALL_CREATE_SYMLINKS", "Whether to create symlinks post install", True )
 )
 
+o.Add(
+	"INCLUDE_PATHS",
+	"Locations on which to search for include files for the dependencies.",
+	[],
+)
 
 # Test options
 
@@ -788,20 +793,41 @@ env.Append(
 		"-DBOOST_BIND_GLOBAL_PLACEHOLDERS",
 	]
 )
-systemIncludeArgument = "/external:I" if env[ "PLATFORM" ] == "win32" else "-isystem"
 
-# update the include and lib paths
-dependencyIncludes = [
-	systemIncludeArgument, "$BOOST_INCLUDE_PATH",
-	systemIncludeArgument, "$OPENEXR_INCLUDE_PATH",
-	systemIncludeArgument, "$ILMBASE_INCLUDE_PATH",
-	systemIncludeArgument, "$TBB_INCLUDE_PATH",
-	systemIncludeArgument, "$BLOSC_INCLUDE_PATH",
+def includeFlags( includeEnv, includeVar ) :
+	systemIncludeArgument = "/external:I" if includeEnv[ "PLATFORM" ] == "win32" else "-isystem"
+	value = includeEnv.get( includeVar )
+	if not value :
+		return []
+
+	if isinstance( value, list ) :
+		result = []
+		for v in value :
+			result.extend( [ systemIncludeArgument, v ] )
+
+		return result
+
+	result = [ systemIncludeArgument, value ]
+
 	# we use "OpenEXR/x.h" and they use "x.h"
-	systemIncludeArgument, os.path.join( "$OPENEXR_INCLUDE_PATH","OpenEXR" ),
-	systemIncludeArgument, os.path.join( "$ILMBASE_INCLUDE_PATH","Imath" ),
-	systemIncludeArgument, "$FREETYPE_INCLUDE_PATH",
-]
+	if includeVar == "OPENEXR_INCLUDE_PATH":
+		result.extend( [ systemIncludeArgument, os.path.join( value, "OpenEXR" ) ] )
+	elif includeVar == "ILMBASE_INCLUDE_PATH":
+		result.extend( [ systemIncludeArgument, os.path.join( value, "Imath" ) ] )
+
+	return result
+
+
+# update the include and lib paths
+dependencyIncludes = []
+dependencyIncludes.extend( includeFlags( env, "BOOST_INCLUDE_PATH" ) )
+dependencyIncludes.extend( includeFlags( env, "OPENEXR_INCLUDE_PATH" ) )
+dependencyIncludes.extend( includeFlags( env, "ILMBASE_INCLUDE_PATH" ) )
+dependencyIncludes.extend( includeFlags( env, "TBB_INCLUDE_PATH" ) )
+dependencyIncludes.extend( includeFlags( env, "BLOSC_INCLUDE_PATH" ) )
+dependencyIncludes.extend( includeFlags( env, "FREETYPE_INCLUDE_PATH" ) )
+
+dependencyIncludes.extend( includeFlags( env, "INCLUDE_PATHS" ) )
 
 env.Prepend(
 	LIBPATH = [
@@ -1186,7 +1212,8 @@ if env["PLATFORM"] != "win32" :
 	if basePythonEnv["PYTHON_INCLUDE_PATH"]=="" :
 		basePythonEnv["PYTHON_INCLUDE_FLAGS"] = getPythonConfig( basePythonEnv, "--includes" ).split()
 	else :
-		basePythonEnv["PYTHON_INCLUDE_FLAGS"] = [ systemIncludeArgument, "$PYTHON_INCLUDE_PATH" ]
+
+		basePythonEnv["PYTHON_INCLUDE_FLAGS"] = includeFlags( env, "PYTHON_INCLUDE_PATH" )
 
 	basePythonEnv.Append( CXXFLAGS = "$PYTHON_INCLUDE_FLAGS" )
 
@@ -1611,9 +1638,8 @@ imageEnvPrepends = {
 		"OpenImageIO$OIIO_LIB_SUFFIX",
 	],
 	"CXXFLAGS" : [
-		"-DIECoreImage_EXPORTS",
-		systemIncludeArgument, "$OIIO_INCLUDE_PATH"
-	]
+		"-DIECoreImage_EXPORTS"
+	] + includeFlags( imageEnv, "OIIO_INCLUDE_PATH" )
 }
 if imageEnv.get( "WITH_OIIO_UTIL", True ):
 	imageEnvPrepends["LIBS"].append( "OpenImageIO_Util$OIIO_LIB_SUFFIX" )
@@ -1807,10 +1833,7 @@ vdbEnvPrepends = {
 		"$VDB_LIB_PATH",
 	],
 	"LIBS" : ["openvdb$VDB_LIB_SUFFIX"],
-	"CXXFLAGS" : [
-		systemIncludeArgument, "$VDB_INCLUDE_PATH",
-		systemIncludeArgument, "$PYBIND11_INCLUDE_PATH",
-	]
+	"CXXFLAGS" : includeFlags( vdbEnv, "VDB_INCLUDE_PATH" )  + includeFlags( vdbEnv, "PYBIND11_INCLUDE_PATH" )
 }
 
 vdbEnv.Prepend( **vdbEnvPrepends)
@@ -1908,10 +1931,8 @@ if env["WITH_GL"] and doConfigure :
 			# while still using -Werror.
 			"-Wno-format" if env["PLATFORM"] != "win32" else "",
 			"-Wno-strict-aliasing" if env["PLATFORM"] != "win32" else "",
-			"/wd4701" if env["PLATFORM"] == "win32" else "",
-			systemIncludeArgument, "$GLEW_INCLUDE_PATH",
-			systemIncludeArgument, "$OIIO_INCLUDE_PATH",
-		],
+			"/wd4701" if env["PLATFORM"] == "win32" else ""
+		] + includeFlags( glEnv, "GLEW_INCLUDE_PATH" ) + includeFlags( glEnv, "OIIO_INCLUDE_PATH" ),
 		"LIBPATH" : [
 			"$GLEW_LIB_PATH",
 			"$OIIO_LIB_PATH",
@@ -2112,10 +2133,8 @@ usdEnvAppends = {
 		# This warning is already disabled generally for release builds,
 		# but also requires disabling for debug builds with USD.
 		"/wd4702" if env["PLATFORM"] == "win32" else "",
-		"-DIECoreUSD_EXPORTS",
-		systemIncludeArgument, "$USD_INCLUDE_PATH",
-		systemIncludeArgument, "$PYTHON_INCLUDE_PATH",
-	],
+		"-DIECoreUSD_EXPORTS"
+	] + includeFlags( usdEnv, "USD_INCLUDE_PATH" ) + includeFlags( usdEnv, "PYTHON_INCLUDE_PATH" ),
 	"CPPPATH" : [
 		"contrib/IECoreUSD/include",
 		"contrib/IECoreUSD/src",
@@ -2267,10 +2286,7 @@ alembicEnvSets = {
 alembicEnv = env.Clone( **alembicEnvSets )
 
 alembicEnvPrepends = {
-	"CXXFLAGS" : [
-		systemIncludeArgument, "$ALEMBIC_INCLUDE_PATH",
-		systemIncludeArgument, "$HDF5_INCLUDE_PATH",
-	],
+	"CXXFLAGS" : includeFlags( alembicEnv, "ALEMBIC_INCLUDE_PATH" ) + includeFlags( alembicEnv, "HDF5_INCLUDE_PATH" ),
 	"CPPPATH" : [
 		"contrib/IECoreAlembic/include",
 	],