bpfix: remove empty HIDL libs

libhidltransport/libhwbinder are empty and disallowed in Android.bp
(motivation is ~4kb per empty library per process overhead).

Bug: 135686713
Test: bpfix
Change-Id: I964215ad35068465217af74c5ef1322b43476428

bpfix/bpfix/bpfix.go

@@ -116,6 +116,10 @@ var fixSteps = []FixStep{
 		Name: "rewriteAndroidAppImport",
 		Fix:  rewriteAndroidAppImport,
 	},
+	{
+		Name: "removeEmptyLibDependencies",
+		Fix:  removeEmptyLibDependencies,
+	},
 }
 
 func NewFixRequest() FixRequest {
@@ -650,6 +654,50 @@ func rewriteAndroidAppImport(f *Fixer) error {
 	return nil
 }
 
+// Removes library dependencies which are empty (and restricted from usage in Soong)
+func removeEmptyLibDependencies(f *Fixer) error {
+	emptyLibraries := []string{
+		"libhidltransport",
+		"libhwbinder",
+	}
+	relevantFields := []string{
+		"export_shared_lib_headers",
+		"export_static_lib_headers",
+		"static_libs",
+		"whole_static_libs",
+		"shared_libs",
+	}
+	for _, def := range f.tree.Defs {
+		mod, ok := def.(*parser.Module)
+		if !ok {
+			continue
+		}
+		for _, field := range relevantFields {
+			listValue, ok := getLiteralListProperty(mod, field)
+			if !ok {
+				continue
+			}
+			newValues := []parser.Expression{}
+			for _, v := range listValue.Values {
+				stringValue, ok := v.(*parser.String)
+				if !ok {
+					return fmt.Errorf("Expecting string for %s.%s fields", mod.Type, field)
+				}
+				if inList(stringValue.Value, emptyLibraries) {
+					continue
+				}
+				newValues = append(newValues, stringValue)
+			}
+			if len(newValues) == 0 && len(listValue.Values) != 0 {
+				removeProperty(mod, field)
+			} else {
+				listValue.Values = newValues
+			}
+		}
+	}
+	return nil
+}
+
 // Converts the default source list property, 'srcs', to a single source property with a given name.
 // "LOCAL_MODULE" reference is also resolved during the conversion process.
 func convertToSingleSource(mod *parser.Module, srcPropertyName string) {
@@ -1084,3 +1132,12 @@ func removeProperty(mod *parser.Module, propertyName string) {
 	}
 	mod.Properties = newList
 }
+
+func inList(s string, list []string) bool {
+	for _, v := range list {
+		if s == v {
+			return true
+		}
+	}
+	return false
+}

bpfix/bpfix/bpfix_test.go

@@ -833,3 +833,57 @@ func TestRewriteAndroidAppImport(t *testing.T) {
 		})
 	}
 }
+
+func TestRemoveEmptyLibDependencies(t *testing.T) {
+	tests := []struct {
+		name string
+		in   string
+		out  string
+	}{
+		{
+			name: "remove sole shared lib",
+			in: `
+				cc_library {
+					name: "foo",
+					shared_libs: ["libhwbinder"],
+				}
+			`,
+			out: `
+				cc_library {
+					name: "foo",
+
+				}
+			`,
+		},
+		{
+			name: "remove a shared lib",
+			in: `
+				cc_library {
+					name: "foo",
+					shared_libs: [
+						"libhwbinder",
+						"libfoo",
+						"libhidltransport",
+					],
+				}
+			`,
+			out: `
+				cc_library {
+					name: "foo",
+					shared_libs: [
+
+						"libfoo",
+
+					],
+				}
+			`,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			runPass(t, test.in, test.out, func(fixer *Fixer) error {
+				return removeEmptyLibDependencies(fixer)
+			})
+		})
+	}
+}