add 'list-prompts' and 'change-prompt' commands.

the list-prompts command shows a list of available prompts as well
as the active prompt in the list. prompts are drawn with a name as
well as a short description.

change-prompt can be used to change the prompt by the name found in
the list-prompts command.

CHANGELOG.md

@@ -27,6 +27,10 @@
 * Add option to disable input completer through `_pry_.config.completer = nil`
 * Add `Pry.main`. returns a special instance of Object referenced by self of `TOPLEVEL_BINDING`: "main".
 * Add `Pry::LastException` (#1145)
+* Add `list-prompts` command. (#1175)
+  - lists the available prompts available for use.
+* Add `change-prompt` command. (#1175)
+  - switch the current prompt, by name.
 
 #### Bug fixes, etc.
 * Move `Pry::BondCompleter` and bond integration to the [pry-bond](https://github.com/pry/pry-bond) rubygem. (#1166)

lib/pry.rb

@@ -174,3 +174,4 @@ require 'pry/editor'
 require 'pry/rubygem'
 require "pry/indent"
 require "pry/last_exception"
+require "pry/prompt"

lib/pry/commands/change_prompt.rb

@@ -0,0 +1,24 @@
+class Pry::Command::ChangePrompt < Pry::ClassCommand
+  match 'change-prompt'
+  group 'prompts'
+  description 'change the current pry prompt'
+  command_options argument_required: true
+  banner <<-BANNER
+    Usage: change-prompt
+    change the current prompt. see list-prompts for a list of available prompts.
+  BANNER
+
+  def process(prompt)
+    if prompt_map.key?(prompt)
+      _pry_.prompt = prompt_map[prompt][:value]
+    else
+      raise Pry::CommandError, "'#{prompt}' isn't a known prompt!"
+    end
+  end
+
+private
+  def prompt_map
+    Pry::Prompt::MAP
+  end
+  Pry::Commands.add_command(self)
+end

lib/pry/commands/list_prompts.rb

@@ -0,0 +1,33 @@
+class Pry::Command::ListPrompts < Pry::ClassCommand
+  match 'list-prompts'
+  group 'prompts'
+  description 'list the prompts available for use in pry'
+  banner <<-BANNER
+    Usage: list-prompts
+    list the prompts available for use in pry
+  BANNER
+
+  def process
+    output.puts heading("Available prompts") + "\n"
+    prompt_map.each do |name, prompt|
+      output.write "name: #{text.bold(name)}"
+      output.puts selected_prompt?(prompt) ? selected_text : ""
+      output.puts prompt[:description]
+      output.puts
+    end
+  end
+
+private
+  def prompt_map
+    Pry::Prompt::MAP
+  end
+
+  def selected_text
+    text.red " (selected) "
+  end
+
+  def selected_prompt?(prompt)
+    _pry_.prompt == prompt[:value]
+  end
+  Pry::Commands.add_command(self)
+end

lib/pry/prompt.rb

@@ -0,0 +1,23 @@
+class Pry::Prompt
+  MAP = {
+    "default" => {
+      value: Pry::DEFAULT_PROMPT,
+      description: "the default pry prompt"
+    },
+
+    "simple" => {
+      value: Pry::SIMPLE_PROMPT,
+      description: "a simple prompt"
+    },
+
+    "nav" => {
+      value: Pry::NAV_PROMPT,
+      description: "a prompt that draws the binding stack as a path and includes information about _in_ and _out_"
+    },
+
+    "none" => {
+      value: Pry::NO_PROMPT,
+      description: "wave goodbye to the pry prompt"
+    }
+ }
+end