Add support for regexp passed to String#index

There are some edge cases I skipped fow now. I thought I would use this
for String#each_line but ended up going a different direction. But this
is still progress.

spec/core/string/index_spec.rb

@@ -0,0 +1,367 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "String#index" do
+  it "raises a TypeError if passed nil" do
+    -> { "abc".index nil }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError if passed a boolean" do
+    -> { "abc".index true }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError if passed a Symbol" do
+    -> { "abc".index :a }.should raise_error(TypeError)
+  end
+
+  it "calls #to_str to convert the first argument" do
+    char = mock("string index char")
+    char.should_receive(:to_str).and_return("b")
+    "abc".index(char).should == 1
+  end
+
+  it "calls #to_int to convert the second argument" do
+    offset = mock("string index offset")
+    offset.should_receive(:to_int).and_return(1)
+    "abc".index("c", offset).should == 2
+  end
+
+  it "raises a TypeError if passed an Integer" do
+    -> { "abc".index 97 }.should raise_error(TypeError)
+  end
+end
+
+describe "String#index with String" do
+  it "behaves the same as String#index(char) for one-character strings" do
+    "blablabla hello cruel world...!".split("").uniq.each do |str|
+      chr = str[0]
+      str.index(str).should == str.index(chr)
+
+      0.upto(str.size + 1) do |start|
+        str.index(str, start).should == str.index(chr, start)
+      end
+
+      (-str.size - 1).upto(-1) do |start|
+        str.index(str, start).should == str.index(chr, start)
+      end
+    end
+  end
+
+  it "returns the index of the first occurrence of the given substring" do
+    "blablabla".index("").should == 0
+    "blablabla".index("b").should == 0
+    "blablabla".index("bla").should == 0
+    "blablabla".index("blabla").should == 0
+    "blablabla".index("blablabla").should == 0
+
+    "blablabla".index("l").should == 1
+    "blablabla".index("la").should == 1
+    "blablabla".index("labla").should == 1
+    "blablabla".index("lablabla").should == 1
+
+    "blablabla".index("a").should == 2
+    "blablabla".index("abla").should == 2
+    "blablabla".index("ablabla").should == 2
+  end
+
+  it "doesn't set $~" do
+    $~ = nil
+
+    'hello.'.index('ll')
+    $~.should == nil
+  end
+
+  it "ignores string subclasses" do
+    "blablabla".index(StringSpecs::MyString.new("bla")).should == 0
+    StringSpecs::MyString.new("blablabla").index("bla").should == 0
+    StringSpecs::MyString.new("blablabla").index(StringSpecs::MyString.new("bla")).should == 0
+  end
+
+  it "starts the search at the given offset" do
+    "blablabla".index("bl", 0).should == 0
+    "blablabla".index("bl", 1).should == 3
+    "blablabla".index("bl", 2).should == 3
+    "blablabla".index("bl", 3).should == 3
+
+    "blablabla".index("bla", 0).should == 0
+    "blablabla".index("bla", 1).should == 3
+    "blablabla".index("bla", 2).should == 3
+    "blablabla".index("bla", 3).should == 3
+
+    "blablabla".index("blab", 0).should == 0
+    "blablabla".index("blab", 1).should == 3
+    "blablabla".index("blab", 2).should == 3
+    "blablabla".index("blab", 3).should == 3
+
+    "blablabla".index("la", 1).should == 1
+    "blablabla".index("la", 2).should == 4
+    "blablabla".index("la", 3).should == 4
+    "blablabla".index("la", 4).should == 4
+
+    "blablabla".index("lab", 1).should == 1
+    "blablabla".index("lab", 2).should == 4
+    "blablabla".index("lab", 3).should == 4
+    "blablabla".index("lab", 4).should == 4
+
+    "blablabla".index("ab", 2).should == 2
+    "blablabla".index("ab", 3).should == 5
+    "blablabla".index("ab", 4).should == 5
+    "blablabla".index("ab", 5).should == 5
+
+    "blablabla".index("", 0).should == 0
+
+    NATFIXME 'not sure what is going on here', exception: SpecFailedException do
+      "blablabla".index("", 1).should == 1
+      "blablabla".index("", 2).should == 2
+      "blablabla".index("", 7).should == 7
+      "blablabla".index("", 8).should == 8
+      "blablabla".index("", 9).should == 9
+    end
+  end
+
+  it "starts the search at offset + self.length if offset is negative" do
+    str = "blablabla"
+
+    ["bl", "bla", "blab", "la", "lab", "ab", ""].each do |needle|
+      (-str.length .. -1).each do |offset|
+        str.index(needle, offset).should ==
+        str.index(needle, offset + str.length)
+      end
+    end
+  end
+
+  it "returns nil if the substring isn't found" do
+    "blablabla".index("B").should == nil
+    "blablabla".index("z").should == nil
+    "blablabla".index("BLA").should == nil
+    "blablabla".index("blablablabla").should == nil
+    NATFIXME 'return nil', exception: SpecFailedException do
+      "blablabla".index("", 10).should == nil
+    end
+
+    "hello".index("he", 1).should == nil
+    "hello".index("he", 2).should == nil
+    "I’ve got a multibyte character.\n".index("\n\n").should == nil
+  end
+
+  it "returns the character index of a multibyte character" do
+    "ありがとう".index("が").should == 2
+  end
+
+  it "returns the character index after offset" do
+    "われわれ".index("わ", 1).should == 2
+    "ありがとうありがとう".index("が", 3).should == 7
+  end
+
+  it "returns the character index after a partial first match" do
+    "</</h".index("</h").should == 2
+  end
+
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    char = "れ".encode Encoding::EUC_JP
+    NATFIXME 'check encoding compatibility', exception: SpecFailedException, message: /Encoding::CompatibilityError/ do
+      -> do
+        "あれ".index char
+      end.should raise_error(Encoding::CompatibilityError)
+    end
+  end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.dup.force_encoding(Encoding::US_ASCII).index('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.index('t'.dup.force_encoding(Encoding::US_ASCII)).should == 1
+  end
+
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    NATFIXME 'Implement ISO-2022-JP', exception: ArgumentError, message: 'unknown encoding name - "ISO-2022-JP"' do
+      str = 'abc'.dup.force_encoding("ISO-2022-JP")
+      pattern = 'b'.dup.force_encoding("EUC-JP")
+
+      -> { str.index(pattern) }.should raise_error(Encoding::CompatibilityError, "incompatible character encodings: ISO-2022-JP and EUC-JP")
+    end
+  end
+end
+
+describe "String#index with Regexp" do
+  it "behaves the same as String#index(string) for escaped string regexps" do
+    NATFIXME 'handle escaped regex better', exception: SpecFailedException do
+      ["blablabla", "hello cruel world...!"].each do |str|
+        ["", "b", "bla", "lab", "o c", "d."].each do |needle|
+          regexp = Regexp.new(Regexp.escape(needle))
+          str.index(regexp).should == str.index(needle)
+
+          0.upto(str.size + 1) do |start|
+            str.index(regexp, start).should == str.index(needle, start)
+          end
+
+          (-str.size - 1).upto(-1) do |start|
+            str.index(regexp, start).should == str.index(needle, start)
+          end
+        end
+      end
+    end
+  end
+
+  it "returns the index of the first match of regexp" do
+    "blablabla".index(/bla/).should == 0
+    "blablabla".index(/BLA/i).should == 0
+
+    "blablabla".index(/.{0}/).should == 0
+    "blablabla".index(/.{6}/).should == 0
+    "blablabla".index(/.{9}/).should == 0
+
+    "blablabla".index(/.*/).should == 0
+    "blablabla".index(/.+/).should == 0
+
+    "blablabla".index(/lab|b/).should == 0
+
+    not_supported_on :opal do
+      "blablabla".index(/\A/).should == 0
+      NATFIXME 'fix matching anchors', exception: SpecFailedException do
+        "blablabla".index(/\Z/).should == 9
+        "blablabla".index(/\z/).should == 9
+        "blablabla\n".index(/\Z/).should == 9
+        "blablabla\n".index(/\z/).should == 10
+      end
+    end
+
+    "blablabla".index(/^/).should == 0
+    "\nblablabla".index(/^/).should == 0
+    "b\nablabla".index(/$/).should == 1
+    "bl\nablabla".index(/$/).should == 2
+
+    "blablabla".index(/.l./).should == 0
+  end
+
+  it "sets $~ to MatchData of match and nil when there's none" do
+    NATFIXME 'Set $~', exception: NoMethodError, message: "undefined method `[]' for nil" do
+      'hello.'.index(/.(.)/)
+      $~[0].should == 'he'
+
+      'hello.'.index(/not/)
+      $~.should == nil
+    end
+  end
+
+  ruby_bug "#20421", ""..."3.3" do
+    it "always clear $~" do
+      "a".index(/a/)
+      $~.should_not == nil
+
+      string = "blablabla"
+      string.index(/bla/, string.length + 1)
+      $~.should == nil
+    end
+  end
+
+  it "starts the search at the given offset" do
+    "blablabla".index(/.{0}/, 5).should == 5
+    "blablabla".index(/.{1}/, 5).should == 5
+    "blablabla".index(/.{2}/, 5).should == 5
+    "blablabla".index(/.{3}/, 5).should == 5
+    "blablabla".index(/.{4}/, 5).should == 5
+
+    "blablabla".index(/.{0}/, 3).should == 3
+    "blablabla".index(/.{1}/, 3).should == 3
+    "blablabla".index(/.{2}/, 3).should == 3
+    "blablabla".index(/.{5}/, 3).should == 3
+    "blablabla".index(/.{6}/, 3).should == 3
+
+    "blablabla".index(/.l./, 0).should == 0
+    "blablabla".index(/.l./, 1).should == 3
+    "blablabla".index(/.l./, 2).should == 3
+    "blablabla".index(/.l./, 3).should == 3
+
+    "xblaxbla".index(/x./, 0).should == 0
+    "xblaxbla".index(/x./, 1).should == 4
+    "xblaxbla".index(/x./, 2).should == 4
+
+    not_supported_on :opal do
+      "blablabla\n".index(/\Z/, 9).should == 9
+    end
+  end
+
+  it "starts the search at offset + self.length if offset is negative" do
+    str = "blablabla"
+
+    ["bl", "bla", "blab", "la", "lab", "ab", ""].each do |needle|
+      (-str.length .. -1).each do |offset|
+        str.index(needle, offset).should ==
+        str.index(needle, offset + str.length)
+      end
+    end
+  end
+
+  it "returns nil if the substring isn't found" do
+    "blablabla".index(/BLA/).should == nil
+
+    "blablabla".index(/.{10}/).should == nil
+    "blaxbla".index(/.x/, 3).should == nil
+    "blaxbla".index(/..x/, 2).should == nil
+  end
+
+  it "returns nil if the Regexp matches the empty string and the offset is out of range" do
+    "ruby".index(//,12).should be_nil
+  end
+
+  it "supports \\G which matches at the given start offset" do
+    "helloYOU.".index(/\GYOU/, 5).should == 5
+    "helloYOU.".index(/\GYOU/).should == nil
+
+    re = /\G.+YOU/
+    # The # marks where \G will match.
+    [
+      ["#hi!YOUall.", 0],
+      ["h#i!YOUall.", 1],
+      ["hi#!YOUall.", 2],
+      ["hi!#YOUall.", nil]
+    ].each do |spec|
+
+      start = spec[0].index("#")
+      str = spec[0].delete("#")
+
+      str.index(re, start).should == spec[1]
+    end
+  end
+
+  it "converts start_offset to an integer via to_int" do
+    obj = mock('1')
+    obj.should_receive(:to_int).and_return(1)
+    "RWOARW".index(/R./, obj).should == 4
+  end
+
+  it "returns the character index of a multibyte character" do
+    "ありがとう".index(/が/).should == 2
+  end
+
+  it "returns the character index after offset" do
+    "われわれ".index(/わ/, 1).should == 2
+  end
+
+  it "treats the offset as a character index" do
+    "われわわれ".index(/わ/, 3).should == 3
+  end
+
+  ruby_bug "#19763", ""..."3.3.0" do
+    it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+      re = Regexp.new "れ".encode(Encoding::EUC_JP)
+      -> do
+        "あれ".index re
+      end.should raise_error(Encoding::CompatibilityError, "incompatible encoding regexp match (EUC-JP regexp with UTF-8 string)")
+    end
+  end
+
+  # The exception message was incorrectly "incompatible character encodings: UTF-8 and EUC-JP" before 3.3.0
+  # Still test that the right exception class is used before that.
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    re = Regexp.new "れ".encode(Encoding::EUC_JP)
+    NATFIXME 'check encoding compatibility', exception: SpecFailedException, message: /Encoding::CompatibilityError/ do
+      -> do
+        "あれ".index re
+      end.should raise_error(Encoding::CompatibilityError)
+    end
+  end
+end

spec/core/string/match_spec.rb

@@ -12,12 +12,10 @@
 
 describe "String#=~" do
   it "behaves the same way as index() when given a regexp" do
-    NATFIXME 'Implement Regexp argument in String#index', exception: TypeError, message: 'no implicit conversion of Regexp into String' do
-      ("rudder" =~ /udder/).should == "rudder".index(/udder/)
-      ("boat" =~ /[^fl]oat/).should == "boat".index(/[^fl]oat/)
-      ("bean" =~ /bag/).should == "bean".index(/bag/)
-      ("true" =~ /false/).should == "true".index(/false/)
-    end
+    ("rudder" =~ /udder/).should == "rudder".index(/udder/)
+    ("boat" =~ /[^fl]oat/).should == "boat".index(/[^fl]oat/)
+    ("bean" =~ /bag/).should == "bean".index(/bag/)
+    ("true" =~ /false/).should == "true".index(/false/)
   end
 
   it "raises a TypeError if a obj is a string" do