Print default val if all vals in axis match default val

To avoid verbosity, we currently dedupe keys in axis if its value
matches the value of //conditions:default. For axes where all values
might match the default value, we would effectively drop the common
value.

To fix this, we are now dropping the select statement and not the common
value.

Test: go test ./bp2build
Change-Id: Ic377b93ee2aba971753f6a5e7a62e15d1fcfa2bc

bp2build/build_conversion_test.go

@@ -21,6 +21,7 @@ import (
 
 	"android/soong/android"
 	"android/soong/android/allowlists"
+	"android/soong/bazel"
 	"android/soong/python"
 )
 
@@ -1931,3 +1932,17 @@ func TestGenerateConfigSetting(t *testing.T) {
 		Description:          "Generating API contribution Bazel targets for custom module",
 	})
 }
+
+// If values of all keys in an axis are equal to //conditions:default, drop the axis and print the common value
+func TestPrettyPrintSelectMapEqualValues(t *testing.T) {
+	lla := bazel.LabelListAttribute{
+		Value: bazel.LabelList{},
+	}
+	libFooImplLabel := bazel.Label{
+		Label: ":libfoo.impl",
+	}
+	lla.SetSelectValue(bazel.OsAndInApexAxis, bazel.AndroidAndNonApex, bazel.MakeLabelList([]bazel.Label{libFooImplLabel}))
+	lla.SetSelectValue(bazel.OsAndInApexAxis, bazel.ConditionsDefaultConfigKey, bazel.MakeLabelList([]bazel.Label{libFooImplLabel}))
+	actual, _ := prettyPrintAttribute(lla, 0)
+	android.AssertStringEquals(t, "Print the common value if all keys in an axis have the same value", `[":libfoo.impl"]`, actual)
+}

bp2build/configurability.go

@@ -279,6 +279,10 @@ func prettyPrintSelectMap(selectMap map[string]reflect.Value, defaultValue *stri
 	}
 
 	if len(selects) == 0 {
+		// If there is a default value, and there are no selects for this axis, print that without any selects.
+		if val, exists := selectMap[bazel.ConditionsDefaultSelectKey]; exists {
+			return prettyPrint(val, indent, emitZeroValues)
+		}
 		// No conditions (or all values are empty lists), so no need for a map.
 		return "", nil
 	}