Add soong_config_get

Having a function to get soong config variables
makes it easier to convert to starlark.

Bug: 201700692
Test: m RBC_PRODUCT_CONFIG=1 RBC_BOARD_CONFIG=1 nothing and check output files
Change-Id: I8627555df10d3f66f6154c00be9f0565076f1f94

core/config.mk

@@ -304,7 +304,7 @@ $(eval SOONG_CONFIG_$(strip $1)_$(strip $2):=$3)
 endef
 
 # soong_config_append appends to the value of the variable in the given Soong
-# config namespace. If the varabile does not exist, it will be defined. If the
+# config namespace. If the variable does not exist, it will be defined. If the
 # namespace does not  exist, it will be defined.
 # $1 is the namespace, $2 is the variable name, $3 is the value
 define soong_config_append
@@ -312,6 +312,14 @@ $(call soong_config_define_internal,$1,$2) \
 $(eval SOONG_CONFIG_$(strip $1)_$(strip $2):=$(SOONG_CONFIG_$(strip $1)_$(strip $2)) $3)
 endef
 
+# soong_config_append gets to the value of the variable in the given Soong
+# config namespace. If the namespace or variables does not exist, an
+# empty string will be returned.
+# $1 is the namespace, $2 is the variable name
+define soong_config_get
+$(SOONG_CONFIG_$(strip $1)_$(strip $2))
+endef
+
 # Set the extensions used for various packages
 COMMON_PACKAGE_SUFFIX := .zip
 COMMON_JAVA_PACKAGE_SUFFIX := .jar

core/product_config.rbc

@@ -321,6 +321,11 @@ def _soong_config_append(g, nsname, var, value):
         ns[var] += " " + value
 
 
+def _soong_config_get(g, nsname, var):
+    """Gets to the value of the variable in the namespace."""
+    return g.get(_soong_config_namespaces_key, {}).get(nsname, {}).get(var, None)
+
+
 def _abspath(path):
     """Provided for compatibility, to be removed later."""
     return path
@@ -644,6 +649,7 @@ rblf = struct(
     soong_config_namespace = _soong_config_namespace,
     soong_config_append = _soong_config_append,
     soong_config_set = _soong_config_set,
+    soong_config_get = _soong_config_get,
     abspath = _abspath,
     addprefix = _addprefix,
     addsuffix = _addsuffix,

target/product/runtime_libart.mk

@@ -61,7 +61,7 @@ else
   apex_test_module := art-check-release-apex-gen-fakebin
 endif
 
-ifeq (true,$(SOONG_CONFIG_art_module_source_build)
+ifeq (true,$(call soong_config_get,art_module,source_build))
   PRODUCT_HOST_PACKAGES += $(apex_test_module)
 endif
 

tests/run.rbc

@@ -94,3 +94,6 @@ assert_eq(
 
 assert_eq("S", globals["PLATFORM_VERSION"])
 assert_eq(30, globals["PLATFORM_SDK_VERSION"])
+
+assert_eq("xyz", rblf.soong_config_get(globals, "NS2", "v3"))
+assert_eq(None, rblf.soong_config_get(globals, "NS2", "nonexistant_var"))