add Pry::Prompt.alias_prompt, ref #1628

5 files changed, 95 insertions, 28 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1137a5d4..332b6118 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,8 @@
 ### HEAD
 
-* Add `Pry::Prompt.add_prompt()`, `Pry::Prompt.get_prompt()`, and `Pry::Prompt.remove_prompt()`, for integrating custom prompts with Pry ([#1628](https://github.com/pry/pry/pull/1628))
+* Add `Pry::Prompt.add_prompt()`, `Pry::Prompt.get_prompt()`, `Pry::Prompt.alias_prompt` and
+  `Pry::Prompt.remove_prompt()`, for integrating custom prompts with Pry
+  ([#1628](https://github.com/pry/pry/pull/1628))
 * Add text helpers for background colors ([#1624](https://github.com/pry/pry/pull/1624))
 * Fix string literal methods completion. ([#1590](https://github.com/pry/pry/pull/1590))
 * Make sure Pry::WrappedModule::Candidate#source_location returns non-nil value when `.name` has
diff --git a/lib/pry/commands/change_prompt.rb b/lib/pry/commands/change_prompt.rb
index 4fe32d71..240cd63e 100644
--- a/lib/pry/commands/change_prompt.rb
+++ b/lib/pry/commands/change_prompt.rb
@@ -11,16 +11,13 @@ class Pry::Command::ChangePrompt < Pry::ClassCommand
   BANNER
 
   def process(prompt)
-    if prompt_map.key?(prompt)
-      _pry_.prompt = prompt_map[prompt][:value]
+    if new_prompt = Pry::Prompt.get_prompt(prompt)
+      _pry_.prompt = new_prompt.proc_array
     else
       raise Pry::CommandError, "'#{prompt}' isn't a known prompt!"
     end
   end
 
   private
-  def prompt_map
-    Pry::Prompt::PROMPT_MAP
-  end
   Pry::Commands.add_command(self)
 end
diff --git a/lib/pry/commands/list_prompts.rb b/lib/pry/commands/list_prompts.rb
index 9177a629..169c58b9 100644
--- a/lib/pry/commands/list_prompts.rb
+++ b/lib/pry/commands/list_prompts.rb
@@ -10,26 +10,26 @@ class Pry::Command::ListPrompts < Pry::ClassCommand
   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 heading("Available prompts") + "\n\n"
+    all_prompts.each do |prompt|
+      next if prompt.alias?
+      aliases = Pry::Prompt.aliases_for(prompt.name)
+      output.write "Name: #{text.bold(prompt.name)}"
+      output.puts selected_prompt?(prompt) ? text.green(" [active]") : ""
+      output.puts "Aliases: #{aliases.map(&:name).join(',')}" if aliases.any?
+      output.puts prompt.description
       output.puts
     end
   end
 
   private
-  def prompt_map
-    Pry::Prompt::PROMPT_MAP
-  end
 
-  def selected_text
-    text.red " (selected) "
+  def all_prompts
+    Pry::Prompt.all_prompts
   end
 
   def selected_prompt?(prompt)
-    _pry_.prompt == prompt[:value]
+    _pry_.prompt == prompt.proc_array
   end
   Pry::Commands.add_command(self)
 end
diff --git a/lib/pry/prompt.rb b/lib/pry/prompt.rb
index 2d8bcb36..f20d129d 100644
--- a/lib/pry/prompt.rb
+++ b/lib/pry/prompt.rb
@@ -1,6 +1,43 @@
 module Pry::Prompt
   extend self
   PROMPT_MAP = {}
+  AliasError = Class.new(RuntimeError)
+  PromptInfo = Struct.new(:name, :description, :proc_array, :alias_for) do
+    #
+    # @return [Boolean]
+    #   Returns true if the prompt is an alias of another prompt.
+    #
+    def alias?
+      alias_for != nil
+    end
+  end
+
+  #
+  # @return [Array<PromptInfo>]
+  #   Returns an Array of {PromptInfo} objects.
+  #
+  def all_prompts
+    PROMPT_MAP.values
+  end
+
+  #
+  # @param [String] prompt
+  #   The name of a prompt.
+  #
+  # @return [Array<PromptInfo>]
+  #   Returns an array of aliases for _prompt_, as {PromptInfo} objects.
+  #
+  def aliases_for(prompt)
+    all_prompts.select{|prompt_info| prompt_info.alias_for == prompt.to_s}
+  end
+
+  #
+  # @return [Array<PromptInfo>]
+  #   Returns an array of all prompt aliases, as {PromptInfo} objects.
+  #
+  def aliased_prompts
+    all_prompts.select(&:alias?)
+  end
 
   #
   # Integrate a custom prompt with Pry.
@@ -17,23 +54,20 @@ module Pry::Prompt
   #  A prompt in the form of [proc {}, proc {}].
   #
   def add_prompt(name, description, value)
-    PROMPT_MAP[name.to_s] = {
-      value: value,
-      description: description
-    }
+    PROMPT_MAP[name.to_s] = PromptInfo.new(name, description, value, nil)
   end
 
   #
   # @example
   #
   #   # .pryrc
-  #   Pry.config.prompt = Pry::Prompt.get_prompt('simple')
+  #   Pry.config.prompt = Pry::Prompt.get_prompt('simple').proc_array
   #
-  # @return [Array<Proc,Proc>]
-  #   Returns a prompt in the form of [proc{}, proc{}]
+  # @return [PromptInfo]
+  #   Returns a prompt in the form of a PromptInfo object.
   #
   def get_prompt(name)
-    PROMPT_MAP.key?(name.to_s) and PROMPT_MAP[name.to_s][:value]
+    PROMPT_MAP.key?(name.to_s) and PROMPT_MAP[name.to_s]
   end
 
   #
@@ -41,6 +75,9 @@ module Pry::Prompt
   # It will no longer be visible in the output of "list-prompts" or usable with the
   # "change-prompt" command.
   #
+  # @note
+  #   Aliases are also removed.
+  #
   # @param [String] name
   #   The name of a prompt.
   #
@@ -48,7 +85,30 @@ module Pry::Prompt
   #   Returns truthy if a prompt was deleted, otherwise nil.
   #
   def remove_prompt(name)
-    PROMPT_MAP.delete name.to_s if PROMPT_MAP.key?(name.to_s)
+    name = name.to_s
+    if PROMPT_MAP.key?(name)
+      aliases_for(name).each{|_alias| PROMPT_MAP.delete(_alias.name)}
+      PROMPT_MAP.delete name
+    end
+  end
+
+  #
+  # Provide alternative name for a prompt, which can be used from the list-prompts
+  # and change-prompt commands.
+  #
+  # @param [String] prompt_name
+  #   The name of the prompt to alias.
+  #
+  # @param [String] aliased_prompt
+  #   The name of the aliased prompt.
+  #
+  def alias_prompt(prompt_name, aliased_prompt)
+    if prompt = get_prompt(prompt_name)
+      PROMPT_MAP[aliased_prompt] = PromptInfo.new *[aliased_prompt, prompt.description,
+                                                    prompt.proc_array, prompt_name]
+    else
+      raise AliasError, "prompt '#{prompt}' cannot be aliased because it doesn't exist"
+    end
   end
 
   add_prompt "default",
diff --git a/spec/prompt_spec.rb b/spec/prompt_spec.rb
index 45c21fd6..f2a61604 100644
--- a/spec/prompt_spec.rb
+++ b/spec/prompt_spec.rb
@@ -16,10 +16,9 @@ RSpec.describe Pry::Prompt do
   describe ".add_prompt" do
     specify "it adds a new prompt to Pry" do
       new_prompt = described_class::PROMPT_MAP['prompt-name']
-      expect(new_prompt).to eq(description: "prompt description", value: prompt_value)
       expect(pry_eval("list-prompts")).to include("prompt-name")
       expect(pry_eval("list-prompts")).to include("prompt description")
-      expect(pry_eval("change-prompt prompt-name", "_pry_.prompt")).to eq(prompt_value)
+      expect(pry_eval("change-prompt prompt-name", "_pry_.prompt")).to eq(new_prompt.proc_array)
     end
   end
 
@@ -30,6 +29,15 @@ RSpec.describe Pry::Prompt do
       expect(pry_eval("list-prompts")).to_not include("prompt description")
     end
   end
+
+  describe ".alias_prompt" do
+    specify "creates alias" do
+      described_class.alias_prompt "prompt-name", "prompt-alias"
+      expect(described_class.aliases_for("prompt-name").map(&:name)).to eq(["prompt-alias"])
+      expect(pry_eval("list-prompts")).to include("Aliases: prompt-alias")
+      expect(pry_eval("change-prompt prompt-alias", "_pry_.prompt")).to eq(prompt_value)
+    end
+  end
 end
 
 describe "Prompts" do