# `BoxTurtle.Debug.PipeDebug`
[🔗](https://github.com/twajjo/box_turtle/blob/v0.1.0/lib/debug/pipe_debug.ex#L1)

Injects a `debug/3` function that can be dropped into the middle of a pipe to log a value, returning it unchanged.

Logging is off by default and enabled per module through application configuration, so debug calls can stay in
the code without flooding the logs.

## Usage

    defmodule MyApp.Billing do
      use BoxTurtle.Debug.PipeDebug

      def invoice_total(items) do
        items
        |> Enum.map(& &1.price)
        |> debug("prices")
        |> Enum.sum()
        # Only log suspicious totals.
        |> debug("large total", condition: &(&1 > 10_000))
      end
    end

    # config/dev.exs: log from these modules only
    config :my_app, debug_enabled_modules: [MyApp.Billing]

    # Logger must also let :debug through (the default in dev):
    config :logger, level: :debug

With that config, `MyApp.Billing.invoice_total([%{price: 5}, %{price: 7}])` returns `12` and logs
`prices: [5, 7]`. With `MyApp.Billing` not listed, it returns `12` and logs nothing.

To log at `:info` instead, or to pick the application whose config is read:

    use BoxTurtle.Debug.PipeDebug, application: :my_app, logger_macro: :info

## Options

  * `:application` - the application whose `:debug_enabled_modules` setting is consulted. Defaults to the
    application the using module belongs to, falling back to `:box_turtle`. Useful in tests, where modules
    may not belong to a loaded application.
  * `:logger_module` - defaults to `Logger`. Any module exposing `debug/1` and `info/1` (functions or macros)
    will do; mostly used for testing PipeDebug itself.
  * `:logger_macro` - `:debug` (default) or `:info`, the level messages are logged at.

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*Consult [api-reference.md](api-reference.md) for complete listing*