View Source Credo.Plugin (Credo v1.7.4)

Plugins are module which can provide additional functionality to Credo.

A plugin is basically just a module that provides an init/1 callback.

defmodule CredoDemoPlugin do
  def init(exec) do
    # but what do we do here??
    exec
  end
end

The Credo.Plugin module provides a number of functions for extending Credo's core features.

defmodule CredoDemoPlugin do
  @config_file File.read!(".credo.exs")

  import Credo.Plugin

  def init(exec) do
    exec
    |> register_default_config(@config_file)
    |> register_command("demo", CredoDemoPlugin.DemoCommand)
    |> register_cli_switch(:castle, :string, :X)
    |> prepend_task(:set_default_command, CredoDemoPlugin.SetDemoAsDefaultCommand)
  end
end

Summary

Functions

Appends a Credo.Execution.Task module to Credo's main execution pipeline.

Appends a Credo.Execution.Task module to the execution pipeline of an existing Command.

Prepends a Credo.Execution.Task module to Credo's main execution pipeline.

Prepends a Credo.Execution.Task module to the execution pipeline of an existing Command.

Registers and initializes a Command module with a given name.

Registers the contents of a config file.

Functions

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append_task(exec, group_name, task_mod)

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Appends a Credo.Execution.Task module to Credo's main execution pipeline.

Credo's execution pipeline consists of several steps, each with a group of tasks, which you can hook into.

Appending tasks to these steps is easy:

# credo_demo_plugin.ex
defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    append_task(exec, :set_default_command, CredoDemoPlugin.SetDemoAsDefaultCommand)
  end
end

Note how Credo.Plugin.append_task/3 takes two arguments after the Credo.Execution struct: the name of the group to be modified and the module that should be executed.

The group names of Credo's main pipeline are:

  • :parse_cli_options
  • :initialize_plugins
  • :determine_command
  • :set_default_command
  • :initialize_command
  • :parse_cli_options_final
  • :validate_cli_options
  • :convert_cli_options_to_config
  • :resolve_config
  • :validate_config
  • :run_command
  • :halt_execution

The module appended to these groups should use Credo.Execution.Task:

# credo_demo_plugin/set_demo_as_default_command.ex
defmodule CredoDemoPlugin.SetDemoAsDefaultCommand do
  use Credo.Execution.Task

  alias Credo.CLI.Options

  def call(exec, _opts) do
    set_command(exec, exec.cli_options.command || "demo")
  end

  defp set_command(exec, command) do
    %Execution{exec | cli_options: %Options{exec.cli_options | command: command}}
  end
end

This example would have the effect that typing mix credo would no longer run the built-in Suggest command, but rather our plugin's Demo command.

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append_task(exec, pipeline_key, group_name, task_mod)

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Appends a Credo.Execution.Task module to the execution pipeline of an existing Command.

Credo's commands can also have an execution pipeline of their own, which is executed when the command is used and which you can hook into as well.

Appending tasks to these steps is easy:

# credo_demo_plugin.ex
defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    append_task(exec, Credo.CLI.Command.Suggest.SuggestCommand, :print_after_analysis, CredoDemoPlugin.WriteFile)
  end
end

Note how Credo.Plugin.append_task/4 takes three arguments after the Credo.Execution struct: the pipeline and the name of the group to be modified and the module that should be executed.

Here are the pipeline keys and group names:

  • Credo.CLI.Command.Suggest.SuggestCommand (run via mix credo suggest)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_before_analysis
    • :run_analysis
    • :filter_issues
    • :print_after_analysis
  • Credo.CLI.Command.List.ListCommand (run via mix credo list)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_before_analysis
    • :run_analysis
    • :filter_issues
    • :print_after_analysis
  • Credo.CLI.Command.Diff.DiffCommand (run via mix credo diff)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_previous_analysis
    • :run_analysis
    • :filter_issues
    • :print_after_analysis
    • :filter_issues_for_exit_status
  • Credo.CLI.Command.Info.InfoCommand (run via mix credo info)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_info

The module appended to these groups should use Credo.Execution.Task:

# credo_demo_plugin/write_file.ex
defmodule CredoDemoPlugin.WriteFile do
  use Credo.Execution.Task

  alias Credo.CLI.Options

  def call(exec, _opts) do
    issue_count = exec |> Execution.get_issues() |> Enum.count
    File.write!("demo.json", ~q({"issue_count": #{issue_count}}))

    exec
  end
end

This example would have the effect that running mix credo suggest would write the issue count in a JSON file.

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prepend_task(exec, group_name, task_mod)

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Prepends a Credo.Execution.Task module to Credo's main execution pipeline.

Credo's execution pipeline consists of several steps, each with a group of tasks, which you can hook into.

Prepending tasks to these steps is easy:

# credo_demo_plugin.ex
defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    prepend_task(exec, :set_default_command, CredoDemoPlugin.SetDemoAsDefaultCommand)
  end
end

Note how Credo.Plugin.prepend_task/3 takes two arguments after the Credo.Execution struct: the name of the group to be modified and the module that should be executed.

The group names of Credo's main pipeline are:

  • :parse_cli_options
  • :initialize_plugins
  • :determine_command
  • :set_default_command
  • :initialize_command
  • :parse_cli_options_final
  • :validate_cli_options
  • :convert_cli_options_to_config
  • :resolve_config
  • :validate_config
  • :run_command
  • :halt_execution

The module prepended to these groups should use Credo.Execution.Task:

# credo_demo_plugin/set_demo_as_default_command.ex
defmodule CredoDemoPlugin.SetDemoAsDefaultCommand do
  use Credo.Execution.Task

  alias Credo.CLI.Options

  def call(exec, _opts) do
    set_command(exec, exec.cli_options.command || "demo")
  end

  defp set_command(exec, command) do
    %Execution{exec | cli_options: %Options{exec.cli_options | command: command}}
  end
end

This example would have the effect that typing mix credo would no longer run the built-in Suggest command, but rather our plugin's Demo command.

Link to this function

prepend_task(exec, pipeline_key, group_name, task_mod)

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Prepends a Credo.Execution.Task module to the execution pipeline of an existing Command.

Credo's commands can also have an execution pipeline of their own, which is executed when the command is used and which you can hook into as well.

Prepending tasks to these steps is easy:

# credo_demo_plugin.ex
defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    prepend_task(exec, Credo.CLI.Command.Suggest.SuggestCommand, :print_after_analysis, CredoDemoPlugin.WriteFile)
  end
end

Note how Credo.Plugin.prepend_task/4 takes three arguments after the Credo.Execution struct: the pipeline and the name of the group to be modified and the module that should be executed.

Here are the pipeline keys and group names:

  • Credo.CLI.Command.Suggest.SuggestCommand (run via mix credo suggest)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_before_analysis
    • :run_analysis
    • :filter_issues
    • :print_after_analysis
  • Credo.CLI.Command.List.ListCommand (run via mix credo list)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_before_analysis
    • :run_analysis
    • :filter_issues
    • :print_after_analysis
  • Credo.CLI.Command.Diff.DiffCommand (run via mix credo diff)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_previous_analysis
    • :run_analysis
    • :filter_issues
    • :print_after_analysis
    • :filter_issues_for_exit_status
  • Credo.CLI.Command.Info.InfoCommand (run via mix credo info)

    • :load_and_validate_source_files
    • :prepare_analysis
    • :print_info

The module prepended to these groups should use Credo.Execution.Task:

# credo_demo_plugin/write_file.ex
defmodule CredoDemoPlugin.WriteFile do
  use Credo.Execution.Task

  alias Credo.CLI.Options

  def call(exec, _opts) do
    issue_count = exec |> Execution.get_issues() |> Enum.count
    File.write!("demo.json", ~q({"issue_count": #{issue_count}}))

    exec
  end
end

This example would have the effect that running mix credo suggest would write the issue count in a JSON file.

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register_cli_switch(exec, name, type, alias_name \\ nil, convert_to_param \\ true)

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Adds a CLI switch to Credo.

For demo purposes, we are writing a command called demo (see register_command/3):

# credo_demo_plugin/demo_command.ex
defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    exec
    |> register_command("demo", CredoDemoPlugin.DemoCommand)
  end
end

# credo_demo_plugin/demo_command.ex
defmodule CredoDemoPlugin.DemoCommand do
  alias Credo.CLI.Output.UI
  alias Credo.Execution

  def call(exec, _) do
    castle = Execution.get_plugin_param(exec, CredoDemoPlugin, :castle)

    UI.puts("By the power of #{castle}!")

    exec
  end
end

Since Plugins can be configured by params in .credo.exs, we can add the :castle param:

# .credo.exs
{CredoDemoPlugin, [castle: "Grayskull"]}

And get the following output:

$ mix credo demo
By the power of Grayskull!

Plugins can provide custom CLI options as well, so we can do something like:

$ mix credo demo --castle Winterfell
Unknown switch: --castle

Registering a custom CLI switch for this is easy:

defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    exec
    |> register_command("demo", CredoDemoPlugin.DemoCommand)
    |> register_cli_switch(:castle, :string, :X)
  end
end

Every registered CLI switch is automatically converted into a plugin param of the same name, which is why we get the following output:

$ mix credo demo --castle Winterfell
By the power of Winterfell!

$ mix credo demo -X Camelot
By the power of Camelot!

Plugin authors can also provide a function to control the plugin param's name and value more granularly:

defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    register_cli_switch(exec, :kastle, :string, :X, fn(switch_value) ->
      {:castle, String.upcase(switch_value)}
    end)
  end
end

And get the following output:

$ mix credo demo --kastle Winterfell
By the power of WINTERFELL!
Link to this function

register_command(exec, name, command_mod)

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Registers and initializes a Command module with a given name.

Add new commands

Commands are just modules with a call function and adding new commands is easy.

# credo_demo_plugin.ex
defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    register_command(exec, "demo", CredoDemoPlugin.DemoCommand)
  end
end

# credo_demo_plugin/demo_command.ex
defmodule CredoDemoPlugin.DemoCommand do
  alias Credo.CLI.Output.UI
  alias Credo.Execution

  def call(exec, _) do
    castle = Execution.get_plugin_param(exec, CredoDemoPlugin, :castle)

    UI.puts("By the power of #{castle}!")

    exec
  end
end

Users can use this command by typing

$ mix credo demo
By the power of !

Override an existing command

Since commands are just modules with a call function, overriding existing commands is easy.

defmodule CredoDemoPlugin do
  import Credo.Plugin

  def init(exec) do
    register_command(exec, "explain", CredoDemoPlugin.MyBetterExplainCommand)
  end
end

This example would have the effect that typing mix credo lib/my_file.ex:42 would no longer run the built-in Explain command, but rather our plugin's MyBetterExplain command.

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register_default_config(exec, config_file_string)

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Registers the contents of a config file.

This registers the contents of a config file as default config, loading it after Credo's own default config but before the config files loaded from the current working directory.

defmodule CredoDemoPlugin do
  @config_file File.read!(".credo.exs")

  import Credo.Plugin

  def init(exec) do
    register_default_config(exec, @config_file)
  end
end