Add failing test for gem files paths prefix matching project path

spec/spec_with_project.rb

@@ -72,11 +72,12 @@ def mock_project(sorbet_dependency: true, &block)
         name: String,
         version: String,
         dependencies: T::Array[String],
+        path: String,
         block: T.nilable(T.proc.params(gem: MockGem).bind(MockGem).void),
       ).returns(MockGem)
     end
-    def mock_gem(name, version, dependencies: [], &block)
-      gem = MockGem.new("#{TEST_TMP_PATH}/#{spec_name}/gems/#{name}", name, version, dependencies)
+    def mock_gem(name, version, dependencies: [], path: default_gem_path(name), &block)
+      gem = MockGem.new(path, name, version, dependencies)
       gem.gemspec(gem.default_gemspec_contents)
       gem.instance_exec(gem, &block) if block
       gem
@@ -139,6 +140,11 @@ def assert_stderr_includes(result, snippet)
 
     private
 
+    sig {params(name: String).returns(String)}
+    def default_gem_path(name)
+      "#{TEST_TMP_PATH}/#{spec_name}/gems/#{name}"
+    end
+
     sig { returns(String) }
     def spec_name
       spec_class = T.unsafe(self).class

spec/tapioca/cli/gem_spec.rb

@@ -710,6 +710,20 @@ class Foo::Secret; end
           assert_success_status(result)
         end
 
+        it "must generate RBIs for gems whose folder location starts with the same prefix as project folder" do
+          # Set the gem path so that the project folder is a prefix of the gem folder
+          gem_path = @project.path + "-gem/foo"
+          gem = mock_gem("foo", "0.0.1", path: gem_path)
+
+          @project.require_mock_gem(gem)
+
+          result = @project.tapioca("gem foo")
+
+          assert_stdout_includes(result, "Compiled foo")
+          assert_empty_stderr(result)
+          assert_success_status(result)
+        end
+
         it "must respect exclude option" do
           @project.require_mock_gem(mock_gem("foo", "0.0.1"))
           @project.require_mock_gem(mock_gem("bar", "0.3.0"))