go2bp: Add -limit and -skip-tests to more easily limit imported modules

I wrote these flags primarily for build-tools:external/kythe, where we
only use a subset of the Go packages defined in the project.

-limit allows defining the entry points to keep in the Android.bp, and
the utput will omit everything except those entry points and their
dependencies. This allows the kythe Android.gen.bp file to drop from 195
modules to 31 using two flags, without having to manually exclude the
other 160 packages.

-skip-tests does as you'd expect, though ideally it wouldn't be
necessary. We didn't import all of the test-only dependencies for kythe
into the source tree, so we're not able to build them.

Change-Id: I49e9f12dac53a74c6e05725ee41fb7c0ed8b0cbb

cmd/go2bp/go2bp.go

@@ -88,11 +88,24 @@ var excludes = make(Exclude)
 var excludeDeps = make(Exclude)
 var excludeSrcs = make(Exclude)
 
+type StringList []string
+
+func (l *StringList) String() string {
+	return strings.Join(*l, " ")
+}
+
+func (l *StringList) Set(v string) error {
+	*l = append(*l, strings.Fields(v)...)
+	return nil
+}
+
 type GoModule struct {
 	Dir string
 }
 
 type GoPackage struct {
+	ExportToAndroid bool
+
 	Dir         string
 	ImportPath  string
 	Name        string
@@ -117,7 +130,7 @@ func (g GoPackage) BpModuleType() string {
 
 func (g GoPackage) BpName() string {
 	if g.IsCommand() {
-		return filepath.Base(g.ImportPath)
+		return rewriteNames.GoToBp(filepath.Base(g.ImportPath))
 	}
 	return rewriteNames.GoToBp(g.ImportPath)
 }
@@ -279,6 +292,10 @@ Usage: %s [--rewrite <pkg-prefix>=<replace>] [-exclude <package>] [-regen <file>
      Don't put the specified go package in the dependency lists.
   -exclude-srcs <module>
      Don't put the specified source files in srcs or testSrcs lists.
+  -limit <package>
+     If set, limit the output to the specified packages and their dependencies.
+  -skip-tests
+     If passed, don't write out any test srcs or dependencies to the Android.bp output.
   -regen <file>
      Read arguments from <file> and overwrite it.
 
@@ -286,11 +303,15 @@ Usage: %s [--rewrite <pkg-prefix>=<replace>] [-exclude <package>] [-regen <file>
 	}
 
 	var regen string
+	var skipTests bool
+	limit := StringList{}
 
 	flag.Var(&excludes, "exclude", "Exclude go package")
 	flag.Var(&excludeDeps, "exclude-dep", "Exclude go package from deps")
 	flag.Var(&excludeSrcs, "exclude-src", "Exclude go file from source lists")
 	flag.Var(&rewriteNames, "rewrite", "Regex(es) to rewrite artifact names")
+	flag.Var(&limit, "limit", "If set, only includes the dependencies of the listed packages")
+	flag.BoolVar(&skipTests, "skip-tests", false, "Whether to skip test sources")
 	flag.StringVar(&regen, "regen", "", "Rewrite specified file")
 	flag.Parse()
 
@@ -321,7 +342,8 @@ Usage: %s [--rewrite <pkg-prefix>=<replace>] [-exclude <package>] [-regen <file>
 	}
 	decoder := json.NewDecoder(bytes.NewReader(output))
 
-	pkgs := []GoPackage{}
+	pkgs := []*GoPackage{}
+	pkgMap := map[string]*GoPackage{}
 	for decoder.More() {
 		pkg := GoPackage{}
 		err := decoder.Decode(&pkg)
@@ -329,7 +351,15 @@ Usage: %s [--rewrite <pkg-prefix>=<replace>] [-exclude <package>] [-regen <file>
 			fmt.Fprintf(os.Stderr, "Failed to parse json: %v\n", err)
 			os.Exit(1)
 		}
-		pkgs = append(pkgs, pkg)
+		if len(limit) == 0 {
+			pkg.ExportToAndroid = true
+		}
+		if skipTests {
+			pkg.TestGoFiles = nil
+			pkg.TestImports = nil
+		}
+		pkgs = append(pkgs, &pkg)
+		pkgMap[pkg.ImportPath] = &pkg
 	}
 
 	buf := &bytes.Buffer{}
@@ -337,8 +367,27 @@ Usage: %s [--rewrite <pkg-prefix>=<replace>] [-exclude <package>] [-regen <file>
 	fmt.Fprintln(buf, "// Automatically generated with:")
 	fmt.Fprintln(buf, "// go2bp", strings.Join(proptools.ShellEscapeList(os.Args[1:]), " "))
 
+	var mark func(string)
+	mark = func(pkgName string) {
+		if excludes[pkgName] {
+			return
+		}
+		if pkg, ok := pkgMap[pkgName]; ok && !pkg.ExportToAndroid {
+			pkg.ExportToAndroid = true
+			for _, dep := range pkg.AllImports() {
+				if !excludeDeps[dep] {
+					mark(dep)
+				}
+			}
+		}
+	}
+
+	for _, pkgName := range limit {
+		mark(pkgName)
+	}
+
 	for _, pkg := range pkgs {
-		if excludes[pkg.ImportPath] {
+		if !pkg.ExportToAndroid || excludes[pkg.ImportPath] {
 			continue
 		}
 		if len(pkg.BpSrcs(pkg.GoFiles)) == 0 && len(pkg.BpSrcs(pkg.TestGoFiles)) == 0 {