func ReconcileRules()

in cmd/kazel/kazel.go [276:331]
54 lines of code
15 McCabe index (conditional complexity)

func ReconcileRules(pkgPath string, rules []*build.Rule, managedAttrs []string, dryRun bool) (bool, error) {
	_, path := findBuildFile(pkgPath)
	info, err := os.Stat(path)
	if err != nil && os.IsNotExist(err) {
		f := &build.File{}
		writeRules(f, rules)
		return writeFile(path, f, nil, false, dryRun)
	} else if err != nil {
		return false, err
	}
	if info.IsDir() {
		return false, fmt.Errorf("%q cannot be a directory", path)
	}
	b, err := ioutil.ReadFile(path)
	if err != nil {
		return false, err
	}
	f, err := build.Parse(path, b)
	if err != nil {
		return false, err
	}
	oldRules := make(map[string]*build.Rule)
	for _, r := range f.Rules("") {
		oldRules[r.Name()] = r
	}
	for _, r := range rules {
		o, ok := oldRules[r.Name()]
		if !ok {
			f.Stmt = append(f.Stmt, r.Call)
			continue
		}
		if !RuleIsManaged(o) {
			continue
		}
		reconcileAttr := func(o, n *build.Rule, name string) {
			if e := n.Attr(name); e != nil {
				o.SetAttr(name, e)
			} else {
				o.DelAttr(name)
			}
		}
		for _, attr := range managedAttrs {
			reconcileAttr(o, r, attr)
		}
		delete(oldRules, r.Name())
	}

	for _, r := range oldRules {
		if !RuleIsManaged(r) {
			continue
		}
		f.DelRules(r.Kind(), r.Name())
	}

	return writeFile(path, f, nil, true, dryRun)
}