What version of Phoenix and LiveView are you using? They weren’t available until Phoenix 1.17.

Please show this module.

In general sigils are just a functions with a bit of syntactic sugar (~ notation). Functions and macros are not “magically enabled”. They need to be defined or imported within a module. The only “magic” is that functions and macros defined in Kernel and Kernel.SpecialForms are automatically imported to every module. Since verified routes are not even part of Elixir core we need to define or import them.

# definition
defmodule MyLib do
  defmacro __using__(opts \\ []) do
    quote do
      def sigil_p(string, opts) do
        # …
      end
    end
  end
end

defmodule MyApp do
  # use is short for:
  # require MyLib
  # MyLib.__using__(…)
  use MyLib
end

# import
defmodule MyLib do
  def sigil_p(string, opts) do
    # …
  end 
end

defmodule MyApp do
  import MyLib
  # or use some macro with such import call
  # require MyLib
  # MyLib.macro_with_import_stuff(…)
  # or same macro, but with name __using__ and use call as above
end

When generating phoenix app with:

$ mix archive.install hex phx_new --force
$ mix phx.new drone_shop

it should create a file called drone_shop/lib/drone_shop_web.ex with such code:

defmodule DroneShopWeb do
  # …

  # this calls html_helpers private function …
  def live_view do
    quote do
      use Phoenix.LiveView,
        layout: {DroneShopWeb.Layouts, :app}

      unquote(html_helpers())
    end
  end

  # …

  # this function have some shared code for many parts of your application
  # at the bottom you should another call
  # this time to verified_routes private function
  defp html_helpers do
    quote do
      # …

      # Routes generation with the ~p sigil
      unquote(verified_routes())
    end
  end

  # we are finally here!
  # we are using some module
  # this is the second case I mentioned i.e. import within a macro
  def verified_routes do
    quote do
      use Phoenix.VerifiedRoutes,
        endpoint: DroneShopWeb.Endpoint,
        router: DroneShopWeb.Router,
        statics: DroneShopWeb.static_paths()
    end
  end

  @doc """
  When used, dispatch to the appropriate controller/view/etc.
  """
  # This is called first! It then call a live_view function …
  defmacro __using__(which) when is_atom(which) do
    apply(__MODULE__, which, [])
  end
end

You can find an import call in phoenix source:
https://github.com/phoenixframework/phoenix/blob/7b5cd358aadb507cd90aa3a52e013f9e9e947ac4/lib/phoenix/verified_routes.ex#L121-131

And the definition of said sigil is here:
https://github.com/phoenixframework/phoenix/blob/7b5cd358aadb507cd90aa3a52e013f9e9e947ac4/lib/phoenix/verified_routes.ex#L202-L210

use DroneShopWeb, :verified_routes

Will do it for you

In newly generated projects this code is wrong, because a live_view function should call it. This code would be good only if author would remove said call, but then there would be no question about it …

Verified routes are not enabled by default. Either this use or

use Phoenix.VerifiedRoutes,
  endpoint: MyAppWeb.Endpoint,
  router: MyAppWeb.Router

Is needed for them to work.

Sources:

• Migrating to Verified Routes · The Phoenix Files
• Phoenix.VerifiedRoutes — Phoenix v1.8.8

Not sure what do you mean … They are enabled by default. See my previous post explaining macros expansion. In newly generated phoenix app you can use routes without any extra change …

I am using the latest versions of both

Here is drone_shop/lib/drone_shop_web.ex

defmodule DroneShopWeb do
  @moduledoc """
  The entrypoint for defining your web interface, such
  as controllers, views, channels and so on.

  This can be used in your application as:

      use DroneShopWeb, :controller
      use DroneShopWeb, :view

  The definitions below will be executed for every view,
  controller, etc, so keep them short and clean, focused
  on imports, uses and aliases.

  Do NOT define functions inside the quoted expressions
  below. Instead, define any helper function in modules
  and import those modules here.
  """

  def controller do
    quote do
      use Phoenix.Controller, namespace: DroneShopWeb

      import Plug.Conn
      import DroneShopWeb.Gettext
      alias DroneShopWeb.Router.Helpers, as: Routes
    end
  end

  def view do
    quote do
      use Phoenix.View,
        root: "lib/drone_shop_web/templates",
        namespace: DroneShopWeb

      # Import convenience functions from controllers
      import Phoenix.Controller,
        only: [get_flash: 1, get_flash: 2, view_module: 1, view_template: 1]

      # Include shared imports and aliases for views
      unquote(view_helpers())
    end
  end

  def live_view do
    quote do
      use Phoenix.LiveView,
        layout: {DroneShopWeb.LayoutView, "live.html"}

      unquote(view_helpers())
    end
  end

  def live_component do
    quote do
      use Phoenix.LiveComponent

      unquote(view_helpers())
    end
  end

  def component do
    quote do
      use Phoenix.Component

      unquote(view_helpers())
    end
  end

  def router do
    quote do
      use Phoenix.Router

      import Plug.Conn
      import Phoenix.Controller
      import Phoenix.LiveView.Router
    end
  end

  def channel do
    quote do
      use Phoenix.Channel
      import DroneShopWeb.Gettext
    end
  end

  defp view_helpers do
    quote do
      # Use all HTML functionality (forms, tags, etc)
      use Phoenix.HTML

      # Import LiveView and .heex helpers (live_render, live_patch, <.form>, etc)
      import Phoenix.LiveView.Helpers

      # Import basic rendering functionality (render, render_layout, etc)
      import Phoenix.View

      import DroneShopWeb.ErrorHelpers
      import DroneShopWeb.Gettext
      alias DroneShopWeb.Router.Helpers, as: Routes
    end
  end

  @doc """
  When used, dispatch to the appropriate controller/view/etc.
  """
  defmacro __using__(which) when is_atom(which) do
    apply(__MODULE__, which, [])
  end
end

Do I need to specifically define the verified routes somewhere?

That doesn’t look like it was generated with the latest version. I’m assuming you did an update?

As per @SergeyMoiseev pointed out you need to add:

def verified_routes do
  quote do
    use Phoenix.VerifiedRoutes,
      endpoint: DroneShopWeb.Endpoint,
      router: DroneShopWeb.Router,
      statics: DroneShopWeb.static_paths()
  end
end

Then in the view_helpers function add:

unquote(verified_routes())