Convert ERB code into Ruby before type-checking

Gemfile

@@ -18,3 +18,4 @@ end
 
 # gem "rbs", path: "../rbs"
 gem "rbs", git: "https://github.com/ruby/rbs.git", branch: "master"
+gem "herb", "~> 0.9"

Gemfile.lock

@@ -16,6 +16,7 @@ PATH
       concurrent-ruby (>= 1.1.10)
       csv (>= 3.0.9)
       fileutils (>= 1.1.0)
+      herb (>= 0.9.0)
       json (>= 2.1.0)
       language_server-protocol (>= 3.17.0.4, < 4.0)
       listen (~> 3.0)
@@ -58,6 +59,7 @@ GEM
     erb (6.0.2)
     ffi (1.17.3)
     fileutils (1.8.0)
+    herb (0.9.0)
     i18n (1.14.8)
       concurrent-ruby (~> 1.0)
     io-console (0.8.2)
@@ -122,6 +124,7 @@ PLATFORMS
 
 DEPENDENCIES
   debug
+  herb (~> 0.9)
   majo
   memory_profiler
   minitest (~> 5.25)

lib/steep/source.rb

@@ -1,3 +1,5 @@
+require "herb"
+
 module Steep
   class Source
     attr_reader :buffer
@@ -38,6 +40,8 @@ def self.new_parser
     end
 
     def self.parse(source_code, path:, factory:)
+      source_code = extract_ruby_from_erb(source_code) if path.to_s.end_with?(".erb")
+
       buffer = ::Parser::Source::Buffer.new(path.to_s, 1, source: source_code)
       node, comments = new_parser().parse_with_comments(buffer)
 
@@ -98,6 +102,10 @@ def self.parse(source_code, path:, factory:)
       new(buffer: buffer, path: path, node: node, mapping: map, comments: comments, ignores: ignores)
     end
 
+    def self.extract_ruby_from_erb(source_code)
+      ::Herb.extract_ruby(source_code, semicolons: true, comments: true)
+    end
+
     def self.construct_mapping(node:, annotations:, mapping:, line_range: nil)
       case node.type
       when :if

sig/test/cli_test.rbs

@@ -21,6 +21,10 @@ class CLITest < Minitest::Test
 
   def test_check_failure: () -> untyped
 
+  def test_erb_check_failure: () -> untyped
+
+  def test_erb_check_success: () -> untyped
+
   def test_check_failure_with_formatter: () -> untyped
 
   def test_check_group__target: () -> untyped

steep.gemspec

@@ -52,4 +52,5 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "strscan", ">= 1.0.0"
   spec.add_runtime_dependency "csv", ">= 3.0.9"
   spec.add_runtime_dependency "uri", ">= 0.12.0"
+  spec.add_runtime_dependency "herb", ">= 0.9"
 end

test/cli_test.rb

@@ -125,6 +125,52 @@ def test_check_failure
     end
   end
 
+  def test_erb_check_failure
+    in_tmpdir do
+      (current_dir + "Steepfile").write(<<-EOF)
+target :app do
+  check "app/views/**/*.erb"
+end
+      EOF
+
+      (current_dir + "app").mkdir
+      (current_dir + "app/views").mkdir
+      (current_dir + "app/views/companies").mkdir
+
+      (current_dir + "app/views/companies/_form.html.erb").write(<<-EOF)
+<div> Count: <%= 1 + "2" %> </div>
+      EOF
+
+      stdout, status = sh(*steep, "check")
+
+      refute_predicate status, :success?, stdout
+      assert_match(/Detected 1 problem from 1 file/, stdout)
+    end
+  end
+
+  def test_erb_check_success
+    in_tmpdir do
+      (current_dir + "Steepfile").write(<<-EOF)
+target :app do
+  check "app/views/**/*.erb"
+end
+      EOF
+
+      (current_dir + "app").mkdir
+      (current_dir + "app/views").mkdir
+      (current_dir + "app/views/companies").mkdir
+
+      (current_dir + "app/views/companies/_form.html.erb").write(<<-EOF)
+<div> Count: <%= 1 + 2 %> </div>
+      EOF
+
+      stdout, status = sh(*steep, "check")
+
+      assert_predicate status, :success?, stdout
+      assert_match(/No type error detected\./, stdout)
+    end
+  end
+
   def test_check_failure_with_formatter
     in_tmpdir do
       (current_dir + "Steepfile").write(<<-EOF)

test/test_helper.rb

@@ -72,7 +72,7 @@ def file_scheme
 
   def assert_any(collection, &block)
     assert collection.any?(&block)
-  end 
+  end
 
   # @rbs [T] (_Each[T], ?size: Integer) { (T) -> void } -> void
   def assert_any!(collection, size: nil, &block)