irb lexer: recognize the SIMPLE prompt (#1943)

* irb lexer: recognize the SIMPLE prompt

Added support for IRB's `:SIMPLE` prompt (`>>`), plus some tests
for it and the two other supported prompts (IRB's `:STANDARD` and Pry's
default).

* Update lib/rouge/lexers/irb.rb

Avoid picking output as prompt

+ support for multi-line prompts. Courtesy of @tancnle.

Co-authored-by: Tan Le <numbat@fastmail.com>

---------

Co-authored-by: Tan Le <numbat@fastmail.com>

lib/rouge/lexers/irb.rb

@@ -23,7 +23,13 @@ def lang_lexer
       end
 
       def prompt_regex
-        /^.*?(irb|pry).*?[>"*]/
+        %r(
+          ^.*?
+          (
+            (irb|pry).*?[>"*] |
+            [>"*]>
+          )
+        )x
       end
 
       def allow_comments?

spec/lexers/irb_spec.rb

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*- #
+# frozen_string_literal: true
+
+describe Rouge::Lexers::IRBLexer do
+  let(:subject) { Rouge::Lexers::IRBLexer.new }
+  let(:klass) { Rouge::Lexers::IRBLexer }
+
+  include Support::Lexing
+
+  it "parses IRB's :DEFAULT prompt" do
+    assert_tokens_equal 'irb(main):001:0> self',
+      ['Generic.Prompt', 'irb(main):001:0>'],
+      ['Text.Whitespace', ' '],
+      ['Name.Builtin', 'self']
+  end
+
+  it "parses IRB's :SIMPLE prompt" do
+    assert_tokens_equal '>> self',
+      ['Generic.Prompt', '>>'],
+      ['Text.Whitespace', ' '],
+      ['Name.Builtin', 'self']
+  end
+
+  it "parses Pry's default prompt" do
+    assert_tokens_equal 'pry(main)> self',
+      ['Generic.Prompt', 'pry(main)>'],
+      ['Text.Whitespace', ' '],
+      ['Name.Builtin', 'self']
+  end
+end