product_variables srcs in prebuilt_etc

bp2build conversion handles product_variable srcs

bug: 228353067
Test: prebuilt_etc_conversion_test.go
Change-Id: I82d3a384ee14d4e981d502dd9eb824c87d5ae2c7
diff --git a/bazel/configurability.go b/bazel/configurability.go
index e1cdd4a..7ff202b 100644
--- a/bazel/configurability.go
+++ b/bazel/configurability.go
@@ -295,10 +295,11 @@
 )
 
 // ProductVariableConfigurationAxis returns an axis for the given product variable
-func ProductVariableConfigurationAxis(variable string) ConfigurationAxis {
+func ProductVariableConfigurationAxis(variable string, outerAxis ConfigurationAxis) ConfigurationAxis {
 	return ConfigurationAxis{
 		configurationType: productVariables,
 		subType:           variable,
+		outerAxisType:     outerAxis.configurationType,
 	}
 }
 
@@ -309,6 +310,8 @@
 	// some configuration types (e.g. productVariables) have multiple independent axes, subType helps
 	// distinguish between them without needing to list all 17 product variables.
 	subType string
+	// used to keep track of which product variables are arch variant
+	outerAxisType configurationType
 }
 
 func (ca *ConfigurationAxis) less(other ConfigurationAxis) bool {
diff --git a/bazel/properties.go b/bazel/properties.go
index d82fa64..11f6247 100644
--- a/bazel/properties.go
+++ b/bazel/properties.go
@@ -309,7 +309,19 @@
 	_, containsProductVariables := axisTypes[productVariables]
 	if containsProductVariables {
 		if containsOs || containsArch || containsOsArch {
-			return fmt.Errorf("label attribute could not be collapsed as it has two or more unrelated axes")
+			if containsArch {
+				allProductVariablesAreArchVariant := true
+				for k := range la.ConfigurableValues {
+					if k.configurationType == productVariables && k.outerAxisType != arch {
+						allProductVariablesAreArchVariant = false
+					}
+				}
+				if !allProductVariablesAreArchVariant {
+					return fmt.Errorf("label attribute could not be collapsed as it has two or more unrelated axes")
+				}
+			} else {
+				return fmt.Errorf("label attribute could not be collapsed as it has two or more unrelated axes")
+			}
 		}
 	}
 	if (containsOs && containsArch) || (containsOsArch && (containsOs || containsArch)) {
diff --git a/bazel/properties_test.go b/bazel/properties_test.go
index dc4d5b0..8729381 100644
--- a/bazel/properties_test.go
+++ b/bazel/properties_test.go
@@ -247,13 +247,13 @@
 			OsArchConfigurationAxis: labelListSelectValues{
 				"linux_x86": makeLabelList([]string{"linux_x86_include"}, []string{}),
 			},
-			ProductVariableConfigurationAxis("product_with_defaults"): labelListSelectValues{
+			ProductVariableConfigurationAxis("product_with_defaults", NoConfigAxis): labelListSelectValues{
 				"a":                        makeLabelList([]string{}, []string{"not_in_value"}),
 				"b":                        makeLabelList([]string{"b_val"}, []string{}),
 				"c":                        makeLabelList([]string{"c_val"}, []string{}),
 				ConditionsDefaultConfigKey: makeLabelList([]string{"c_val", "default", "default2"}, []string{}),
 			},
-			ProductVariableConfigurationAxis("product_only_with_excludes"): labelListSelectValues{
+			ProductVariableConfigurationAxis("product_only_with_excludes", NoConfigAxis): labelListSelectValues{
 				"a": makeLabelList([]string{}, []string{"not_in_value"}),
 			},
 		},
@@ -281,7 +281,7 @@
 			"linux_x86":                makeLabels("linux_x86_include"),
 			ConditionsDefaultConfigKey: nilLabels,
 		},
-		ProductVariableConfigurationAxis("product_with_defaults"): {
+		ProductVariableConfigurationAxis("product_with_defaults", NoConfigAxis): {
 			"a":                        nilLabels,
 			"b":                        makeLabels("b_val"),
 			"c":                        makeLabels("c_val"),
@@ -674,7 +674,7 @@
 			OsArchConfigurationAxis: stringListSelectValues{
 				"linux_x86": {"linux_x86_include"},
 			},
-			ProductVariableConfigurationAxis("a"): stringListSelectValues{
+			ProductVariableConfigurationAxis("a", NoConfigAxis): stringListSelectValues{
 				"a": []string{"not_in_value"},
 			},
 		},
@@ -699,7 +699,7 @@
 			"linux": []string{"linux_include"},
 		},
 		OsArchConfigurationAxis: stringListSelectValues{},
-		ProductVariableConfigurationAxis("a"): stringListSelectValues{
+		ProductVariableConfigurationAxis("a", NoConfigAxis): stringListSelectValues{
 			"a": []string{"not_in_value"},
 		},
 	}