[ruby/erb] Revert "Remove safe_level and further positional arguments (https://github.com/ruby/erb/pull/7)"

This reverts commit https://github.com/ruby/erb/commit/5133efa06f0603ae79292f3b2b942957bc8a442e.

While we already handled this deprecation in many libraries, we noticed
that some (e.g. sprockets) relied on the format of `ERB.version` and
https://github.com/ruby/erb/commit/2b4182eb108b9e42fa30bcfa41931896132f88b8 broke such handling.

Given that the `ERB.version` change was released at 3.1 and it's
obviously new, I'll skip this removal in 3.2 and postpone this to a
future version.

4 files changed, 91 insertions, 18 deletions

diff --git a/NEWS.md b/NEWS.md
index 737bc5ea6c..6b50bfd865 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -106,10 +106,6 @@ The following deprecated methods are removed.
 
 ## Stdlib compatibility issues
 
-* ERB
-    * `ERB.new` no longer takes more than one positional arguments
-      [[Feature #14256]]
-
 ## C API updates
 
 ### Removed C APIs
@@ -142,7 +138,6 @@ The following deprecated APIs are removed.
 ## Miscellaneous changes
 
 [Feature #12737]: https://bugs.ruby-lang.org/issues/12737
-[Feature #14256]: https://bugs.ruby-lang.org/issues/14256
 [Feature #14332]: https://bugs.ruby-lang.org/issues/14332
 [Feature #15231]: https://bugs.ruby-lang.org/issues/15231
 [Bug #15928]:     https://bugs.ruby-lang.org/issues/15928
diff --git a/lib/erb.rb b/lib/erb.rb
index 54216330da..0e42425a60 100644
--- a/lib/erb.rb
+++ b/lib/erb.rb
@@ -808,7 +808,20 @@ class ERB
   #  Chicken Fried Steak -- 9.95
   #  A well messages pattie, breaded and fried.
   #
-  def initialize(str, trim_mode: nil, eoutvar: '_erbout')
+  def initialize(str, safe_level=NOT_GIVEN, legacy_trim_mode=NOT_GIVEN, legacy_eoutvar=NOT_GIVEN, trim_mode: nil, eoutvar: '_erbout')
+    # Complex initializer for $SAFE deprecation at [Feature #14256]. Use keyword arguments to pass trim_mode or eoutvar.
+    if safe_level != NOT_GIVEN
+      warn 'Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments.', uplevel: 1
+    end
+    if legacy_trim_mode != NOT_GIVEN
+      warn 'Passing trim_mode with the 3rd argument of ERB.new is deprecated. Use keyword argument like ERB.new(str, trim_mode: ...) instead.', uplevel: 1
+      trim_mode = legacy_trim_mode
+    end
+    if legacy_eoutvar != NOT_GIVEN
+      warn 'Passing eoutvar with the 4th argument of ERB.new is deprecated. Use keyword argument like ERB.new(str, eoutvar: ...) instead.', uplevel: 1
+      eoutvar = legacy_eoutvar
+    end
+
     compiler = make_compiler(trim_mode)
     set_eoutvar(compiler, eoutvar)
     @src, @encoding, @frozen_string = *compiler.compile(str)
diff --git a/test/erb/test_erb.rb b/test/erb/test_erb.rb
index 88097af033..fb5e9b611e 100644
--- a/test/erb/test_erb.rb
+++ b/test/erb/test_erb.rb
@@ -24,6 +24,29 @@ class TestERB < Test::Unit::TestCase
     assert_match(/\Atest filename:1\b/, e.backtrace[0])
   end
 
+  # [deprecated] This will be removed later
+  def test_without_filename_with_safe_level
+    erb = EnvUtil.suppress_warning do
+      ERB.new("<% raise ::TestERB::MyError %>", 1)
+    end
+    e = assert_raise(MyError) {
+      erb.result
+    }
+    assert_match(/\A\(erb\):1\b/, e.backtrace[0])
+  end
+
+  # [deprecated] This will be removed later
+  def test_with_filename_and_safe_level
+    erb = EnvUtil.suppress_warning do
+      ERB.new("<% raise ::TestERB::MyError %>", 1)
+    end
+    erb.filename = "test filename"
+    e = assert_raise(MyError) {
+      erb.result
+    }
+    assert_match(/\Atest filename:1\b/, e.backtrace[0])
+  end
+
   def test_with_filename_lineno
     erb = ERB.new("<% raise ::TestERB::MyError %>")
     erb.filename = "test filename"
@@ -75,16 +98,25 @@ class TestERBCore < Test::Unit::TestCase
   end
 
   def test_core
+    # [deprecated] Fix initializer later
+    EnvUtil.suppress_warning do
+      _test_core(nil)
+      _test_core(0)
+      _test_core(1)
+    end
+  end
+
+  def _test_core(safe)
     erb = @erb.new("hello")
     assert_equal("hello", erb.result)
 
-    erb = @erb.new("hello", trim_mode: 0)
+    erb = @erb.new("hello", safe, 0)
     assert_equal("hello", erb.result)
 
-    erb = @erb.new("hello", trim_mode: 1)
+    erb = @erb.new("hello", safe, 1)
     assert_equal("hello", erb.result)
 
-    erb = @erb.new("hello", trim_mode: 2)
+    erb = @erb.new("hello", safe, 2)
     assert_equal("hello", erb.result)
 
     src = <<EOS
@@ -112,9 +144,9 @@ EOS
 EOS
     erb = @erb.new(src)
     assert_equal(ans, erb.result)
-    erb = @erb.new(src, trim_mode: 0)
+    erb = @erb.new(src, safe, 0)
     assert_equal(ans, erb.result)
-    erb = EnvUtil.suppress_warning { @erb.new(src, trim_mode: '') }
+    erb = @erb.new(src, safe, '')
     assert_equal(ans, erb.result)
 
     ans = <<EOS
@@ -125,9 +157,9 @@ EOS
 * 1% n=0
 * 2
 EOS
-    erb = @erb.new(src, trim_mode: 1)
+    erb = @erb.new(src, safe, 1)
     assert_equal(ans.chomp, erb.result)
-    erb = @erb.new(src, trim_mode: '>')
+    erb = @erb.new(src, safe, '>')
     assert_equal(ans.chomp, erb.result)
 
     ans  = <<EOS
@@ -141,9 +173,9 @@ EOS
 * 2
 EOS
 
-    erb = @erb.new(src, trim_mode: 2)
+    erb = @erb.new(src, safe, 2)
     assert_equal(ans, erb.result)
-    erb = @erb.new(src, trim_mode: '<>')
+    erb = @erb.new(src, safe, '<>')
     assert_equal(ans, erb.result)
 
     ans = <<EOS
@@ -157,7 +189,7 @@ EOS
 * 0
 
 EOS
-    erb = @erb.new(src, trim_mode: '%')
+    erb = @erb.new(src, safe, '%')
     assert_equal(ans, erb.result)
 
     ans = <<EOS
@@ -165,7 +197,7 @@ EOS
 = hello
 * 0* 0* 0
 EOS
-    erb = @erb.new(src, trim_mode: '%>')
+    erb = @erb.new(src, safe, '%>')
     assert_equal(ans.chomp, erb.result)
 
     ans = <<EOS
@@ -175,7 +207,7 @@ EOS
 * 0
 * 0
 EOS
-    erb = @erb.new(src, trim_mode: '%<>')
+    erb = @erb.new(src, safe, '%<>')
     assert_equal(ans, erb.result)
   end
 
@@ -629,6 +661,27 @@ EOS
     end
   end
 
+  # [deprecated] These interfaces will be removed later
+  def test_deprecated_interface_warnings
+    [nil, 0, 1, 2].each do |safe|
+      assert_warn(/2nd argument of ERB.new is deprecated/) do
+        ERB.new('', safe)
+      end
+    end
+
+    [nil, '', '%', '%<>'].each do |trim|
+      assert_warn(/3rd argument of ERB.new is deprecated/) do
+        ERB.new('', nil, trim)
+      end
+    end
+
+    [nil, '_erbout', '_hamlout'].each do |eoutvar|
+      assert_warn(/4th argument of ERB.new is deprecated/) do
+        ERB.new('', nil, nil, eoutvar)
+      end
+    end
+  end
+
   def test_prohibited_marshal_dump
     erb = ERB.new("")
     assert_raise(TypeError) {Marshal.dump(erb)}
diff --git a/test/erb/test_erb_command.rb b/test/erb/test_erb_command.rb
index ef170744c2..0baa59ddd5 100644
--- a/test/erb/test_erb_command.rb
+++ b/test/erb/test_erb_command.rb
@@ -15,4 +15,16 @@ class TestErbCommand < Test::Unit::TestCase
                        File.expand_path("../../libexec/erb", __dir__)],
                       "<%=''.encoding.to_s%>", ["UTF-8"])
   end
+
+  # These interfaces will be removed at Ruby 2.7.
+  def test_deprecated_option
+    warnings = [
+      "warning: -S option of erb command is deprecated. Please do not use this.",
+      /\n.+\/libexec\/erb:\d+: warning: Passing safe_level with the 2nd argument of ERB\.new is deprecated\. Do not use it, and specify other arguments as keyword arguments\.\n/,
+    ]
+    assert_in_out_err(["-I#{File.expand_path('../../lib', __dir__)}", "-w",
+                       File.expand_path("../../libexec/erb", __dir__),
+                       "-S", "0"],
+                      "hoge", ["hoge"], warnings)
+  end
 end