Clouseau is a silly little inspector. Essentialy is an enhancement over the IO.inspect function. It adds the functionality to display the file, module and line number of the calling location. Also it can optionaly display a line under the inspected term, to separate it from other output on the screen and optionaly colorize the output.

Add clouseau to your list of dependencies in mix.exs

def deps do
  [
    #...
    {:clouseau, "~> 0.5.0"}
  ]
end

In order to use Clouseau you first must require the Cl module

require Cl

Clouseau exports two macros: Cl.inspect/2 and Cl.inspect/3. Just use them instead of IO.inspect.

Cl.inspect("test", label: "This is a test")

or if you want colors and a bottom border

Cl.inspect("test", label: "-cb This is a test")

Of course the Cl.inspect/2 macro can be used in a pipe

conn
  |> Cl.inspect(label: "-cb Before magic")
  |> do_some_magic()
  |> Cl.inspect(label: "-cb After magic")

That's it. You can return to your code now.

If you wish to do some customization continue reading below.

Both macros are ready to use out of the box. By default they display the file, module and line where the macro was called, above the label and the inspected term.

clouseau uses OptionParser to parse the switches. The switches can be given directly in the label option. You can use switches to modify what will be shown.

Cl.inspect({"test", 7, %{banana: :yellow}}, label: "--no-file Test showing only module and line")
# Clouseau.ClTest:20
# Test showing only module and line: {"test", 7, %{banana: :yellow}}

Cl.inspect({"test", 7, %{banana: :yellow}}, label: "-b Test With border", syntax_colors: [number: :blue])
# lib/cltest.ex
# Clouseau.ClTest:26
# Test With border: {"test", 7}
# -------------------------------------------------------------------------------------
# {"test", 7}

Switches must be grouped in the beginning of the string. Any non-switch group of characters stops the parser and the rest of the line is treated as the text of the label. For example:

Cl.inspect({"test", 7, [banana: :yellow]}, label: "--no-module --no-line -b Showing only the --file option. The --no-border option has no effect")
# lib/cltest.ex
# Showing only the --file option. The --no-border option has no effect: {"test", 7, [banana: "split"]}
# --------------------------------------------------------------------------------------------------------------------------------------------------

Note: The first space on the label text is always discarded. The rest of the spaces stay there. This is intentional to keep it as consistent as possible with IO.inspect who does not trim white spaces. For example:

Cl.inspect({"test", 7}, label: "-b      Test With border", syntax_colors: [number: :blue])
#lib/cltest.ex
#Clouseau.ClTest:26
#     Test With border: {"test", 7}
#------------------------------------------------------------------------------------------

The distance between the switch and the text is 6 spaces while the result displays 5 spaces. If, for some reason, you depend on IO.inspect not triming the white space, keep this behavior in mind.

If you wish to have your default set of switches you can set options in your config

config :clouseau,
default_switches: [module: true, line: true, file: true, border: true, colors: true]

clouseau uses an EEx template to display the various parts of the label. The template uses a custom engine Clouseau.TemplateEngine instead of the default EEx.SmartEngine. The differences are:

• It doesn't add a line break on tag's end. Instead you shoud add a "\n" where you want a line break. The reason for this change is beacuse this way the line break can be controlled with conditionals.
• It supports a has_val?/1 function that returns false if the value is one of nil, false or "".
• The @ function desn't use Access.fetch/2 but Map.get/2 to get the value. It does not warn or rise any errors. Instead it returns an empty string.
• It can use IO Lists.

The format of the label is not configurable on the fly. If, for example, it is prefered to display the module before the line, this can be changed only by using a diferent template at compile time.

You can use a custom template by setting in your config. Below is shown the default template as an example.

config :clouseau,
template: """
<% import IO.ANSI %>
<%= if has_val?(file), do: from_iolist [:blue,  @file, :reset, "\n"] %>
<%= if has_val?(module), do: from_iolist [:green, @module, ":"] %>
<%= if has_val?(line), do:  from_iolist [:red, @line] %>
<%= if has_val?(module) || has_val?(line), do: from_iolist [:reset, "\n"] %>
<%= if has_val?(text), do: from_iolist [:yellow, @text, :reset, ": "] %>
"""

The colors for the inspected term are choosen to match those of iex. If you wish to change any of the default colors you can do so in your config

config :clouseau,
  syntax_colors: [
    string: :red,
    number: :yellow
]

The above snipet will replace the default colors for strings and numbers.

Or directly in you macro call

%{
  "doors" => 2,
  "windows" => 5,
} 
|> Cl.inspect(label: "-bc Test with border and colors", syntax_colors: [number: :red])

If the syntax_colors option is used in the macro call, then the default colors or colors used in the syntax_colors option in config.exs are not used.

%{
  :answer => 42,
  :comment => "The Answer to the Ultimate Question of Life, The Universe, and Everything."

} 
|> Cl.inspect(syntax_colors: [number: :red])

In the above snippet, only the numbers will be colored.

If colors are defined in config.exs they will be merged with the default colors. Any defined color will override the default.

Colors can be displayed either by using the -c switch in the call, by defining the colors: true in config.exs or the syntax_colors option in the call.

clouseau provides two custom credo checks: Clouseau.Check.Warning.ClInspect and Clouseau.Check.Warning.RequireCl. To use them just append them to the :checks option in your .credo.exs file.

checks: [

  # ... some checks

  # Custom checks can be created using `mix credo.gen.check`.
  #

  {Clouseau.Check.Warning.ClInspect},
  {Clouseau.Check.Warning.RequireCl},
]

• Add some tests
• Add dialyzer documentation