render.go

// option 1:
// actions/render.go
"isCurrentPathName": func(name string, help plush.HelperContext) bool {
	if cp, ok := help.Value("current_route").(buffalo.RouteInfo); ok {
		return cp.PathName == name
	}
	return false
},

// template.html
// <div class="menu__item<%= if (isCurrentPathName("rootPath")) { %>--active<% } %>">Home</div>
// or
// <div class="menu__item<%= if (isCurrentPathName("rootPath")) { "--active" } %>">Home</div>

// option 2:
// actions/render.go
"isActiveMenu": func(name string, help plush.HelperContext) string {
	if cp, ok := help.Value("current_route").(buffalo.RouteInfo); ok {
		if cp.PathName == name {
			return "--active"
		}
	}
	return ""
},

// template.html
// <div class="menu__item<%= isActiveMenu("rootPath")  %>">Home</div>