Accept a module attribute as the private: option of a localized route

[rubas]

Before

A localized route whose private: option is a module attribute:

@page_private %{section: :docs}

localize [:en, :fr] do
  get "/#{locale}/sections/:page", PageController, :show, private: @page_private
end

The router does not compile:

** (FunctionClauseError) no function clause matching in Localize.Routes.put_value/3
    # 1
    {:@, [line: 79, column: 70], [{:page_private, [line: 79, column: 71], nil}]}
    # 2
    :localize_locale
    lib/localize/routes.ex:701: Localize.Routes.put_value/3

Problem

• localize/1 adds the locale to the private: (or assigns:) option, but only when that option is a literal map.
• A module attribute, or any other expression, reaches the macro as AST, and no clause of put_value/3 matches it.

After

The same route compiles. A request to /fr/sections/1 has both values in conn.private:

%{section: :docs, localize_locale: :fr}

Details

Cause. Localize.Routes.put_value/3 has a clause for nil and one for a literal map ({:%{}, meta, key_values}), nothing else.

Fix. A third clause wraps any other expression in Map.put/3, so the map is built at runtime, when the attribute has its value. The two existing clauses stay, so a literal map still merges at compile time.

Tests. test/support/router.ex gets a route with private: @page_private; test/routes_test.exs checks that /fr/sections/1 has section: :docs and the locale fr in conn.private. Without the fix the test router does not compile.

Checks. mix test (268 passed), mix format --check-formatted, mix compile --warnings-as-errors, mix credo --strict (one existing finding, unchanged).

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