fix(samples): de-overfit no_implicit_null_initial (inflector false positive)

priv/combined_metrics/samples/type_and_value/no_implicit_null_initial/bad/pricing.ex

@@ -0,0 +1,63 @@
+defmodule Pricing.Bad do
+  @moduledoc """
+  Price resolution — BAD: values initialized to nil then assigned in branches.
+  """
+
+  def quote(cart, customer) do
+    base = nil
+    discount = nil
+    shipping = nil
+
+    base = subtotal(cart)
+
+    if customer.tier == :gold do
+      discount = div(base, 10)
+    end
+
+    if discount == nil do
+      discount = 0
+    end
+
+    if customer.tier == :gold do
+      shipping = 0
+    else
+      shipping = 499
+    end
+
+    %{base: base, discount: discount, shipping: shipping, total: base - discount + shipping}
+  end
+
+  def discount_for(customer, base) do
+    discount = nil
+
+    if customer.tier == :gold do
+      discount = div(base, 10)
+    end
+
+    if customer.tier == :silver do
+      discount = div(base, 20)
+    end
+
+    if discount == nil do
+      discount = 0
+    end
+
+    discount
+  end
+
+  def coupon_value(coupon, base) do
+    value = nil
+
+    if coupon != nil do
+      value = div(base * coupon.value, 100)
+    end
+
+    if value == nil do
+      value = 0
+    end
+
+    value
+  end
+
+  defp subtotal(cart), do: Enum.reduce(cart, 0, &(&1.price * &1.qty + &2))
+end

priv/combined_metrics/samples/type_and_value/no_implicit_null_initial/bad/router.ex

@@ -0,0 +1,50 @@
+defmodule Router.Bad do
+  @moduledoc """
+  Request routing — BAD: handler starts nil and is set in branch after branch.
+  """
+
+  def dispatch(request) do
+    handler = nil
+
+    if request.method == :get and request.path == "/health" do
+      handler = &health/1
+    end
+
+    if request.method == :get and request.path == "/users" do
+      handler = &list_users/1
+    end
+
+    if request.method == :post and request.path == "/users" do
+      handler = &create_user/1
+    end
+
+    if handler == nil do
+      handler = &not_found/1
+    end
+
+    handler.(request)
+  end
+
+  def status_for(result) do
+    status = nil
+
+    if match?({:ok, _}, result) do
+      status = 200
+    end
+
+    if result == {:error, :not_found} do
+      status = 404
+    end
+
+    if status == nil do
+      status = 500
+    end
+
+    status
+  end
+
+  defp health(_request), do: {:ok, %{status: "up"}}
+  defp list_users(_request), do: {:ok, []}
+  defp create_user(_request), do: {:ok, %{id: 1}}
+  defp not_found(_request), do: {:error, :not_found}
+end

priv/combined_metrics/samples/type_and_value/no_implicit_null_initial/bad/session.ex

@@ -0,0 +1,57 @@
+defmodule Session.Bad do
+  @moduledoc """
+  Session building — BAD: nil placeholders filled in across nested branches.
+  """
+
+  def build(conn, store) do
+    user = nil
+    token = nil
+    prefs = nil
+
+    token = conn.cookies["session"]
+
+    if token != nil do
+      user = store.lookup(token)
+
+      if user != nil do
+        prefs = store.preferences(user.id)
+      end
+    end
+
+    if user == nil do
+      {:error, :unauthenticated}
+    else
+      {:ok, %{user: user, token: token, preferences: prefs}}
+    end
+  end
+
+  def current_role(session) do
+    role = nil
+
+    if session != nil do
+      if session.user != nil do
+        role = session.user.role
+      end
+    end
+
+    if role == nil do
+      role = :guest
+    end
+
+    role
+  end
+
+  def expires_at(session, now) do
+    ttl = nil
+
+    if current_role(session) == :admin do
+      ttl = 3_600
+    end
+
+    if ttl == nil do
+      ttl = 1_800
+    end
+
+    now + ttl
+  end
+end

priv/combined_metrics/samples/type_and_value/no_implicit_null_initial/good/pricing.ex

@@ -0,0 +1,35 @@
+defmodule Pricing.Good do
+  @moduledoc """
+  Price resolution — GOOD: each value comes straight from an expression.
+  """
+
+  def quote(cart, customer) do
+    base = subtotal(cart)
+    discount = discount_for(customer, base)
+    shipping = shipping_for(cart, customer)
+
+    %{base: base, discount: discount, shipping: shipping, total: base - discount + shipping}
+  end
+
+  def discount_for(customer, base) do
+    case customer.tier do
+      :gold -> div(base, 10)
+      :silver -> div(base, 20)
+      _ -> 0
+    end
+  end
+
+  def shipping_for(cart, customer) do
+    cond do
+      customer.tier == :gold -> 0
+      subtotal(cart) >= 5_000 -> 0
+      true -> 499
+    end
+  end
+
+  def coupon_value(nil, _base), do: 0
+  def coupon_value(%{type: :percent, value: value}, base), do: div(base * value, 100)
+  def coupon_value(%{type: :flat, value: value}, _base), do: value
+
+  defp subtotal(cart), do: Enum.reduce(cart, 0, &(&1.price * &1.qty + &2))
+end

priv/combined_metrics/samples/type_and_value/no_implicit_null_initial/good/router.ex

@@ -0,0 +1,35 @@
+defmodule Router.Good do
+  @moduledoc """
+  Request routing — GOOD: the handler is the value of a single case expression.
+  """
+
+  def dispatch(request) do
+    handler =
+      case {request.method, request.path} do
+        {:get, "/health"} -> &health/1
+        {:get, "/users"} -> &list_users/1
+        {:post, "/users"} -> &create_user/1
+        {_, _} -> &not_found/1
+      end
+
+    handler.(request)
+  end
+
+  def status_for(result) do
+    case result do
+      {:ok, _} -> 200
+      {:error, :not_found} -> 404
+      {:error, :invalid} -> 422
+      {:error, _} -> 500
+    end
+  end
+
+  def content_type(request) do
+    Map.get(request.headers, "accept", "application/json")
+  end
+
+  defp health(_request), do: {:ok, %{status: "up"}}
+  defp list_users(_request), do: {:ok, []}
+  defp create_user(_request), do: {:ok, %{id: 1}}
+  defp not_found(_request), do: {:error, :not_found}
+end

priv/combined_metrics/samples/type_and_value/no_implicit_null_initial/good/session.ex

@@ -0,0 +1,39 @@
+defmodule Session.Good do
+  @moduledoc """
+  Session building — GOOD: values bound once from with/case results.
+  """
+
+  def build(conn, store) do
+    with {:ok, token} <- read_token(conn),
+         {:ok, user} <- store.lookup(token),
+         {:ok, prefs} <- store.preferences(user.id) do
+      {:ok, %{user: user, token: token, preferences: prefs}}
+    else
+      :no_token -> {:error, :unauthenticated}
+      {:error, reason} -> {:error, reason}
+    end
+  end
+
+  def current_role(session) do
+    case session do
+      %{user: %{role: role}} -> role
+      _ -> :guest
+    end
+  end
+
+  def expires_at(session, now) do
+    ttl = ttl_for(current_role(session))
+    now + ttl
+  end
+
+  defp ttl_for(:admin), do: 3_600
+  defp ttl_for(:guest), do: 300
+  defp ttl_for(_), do: 1_800
+
+  defp read_token(conn) do
+    case conn.cookies["session"] do
+      nil -> :no_token
+      token -> {:ok, token}
+    end
+  end
+end