1 files changed, 79 insertions, 0 deletions
diff --git a/spec/mspec/lib/mspec/runner/actions/constants_leak_checker.rb b/spec/mspec/lib/mspec/runner/actions/constants_leak_checker.rb
new file mode 100644
index 0000000000..fd0a3efe14
--- /dev/null
+++ b/spec/mspec/lib/mspec/runner/actions/constants_leak_checker.rb
@@ -0,0 +1,79 @@
+class ConstantsLockFile
+  LOCK_FILE_NAME = '.mspec.constants'
+
+  def self.load
+    if File.exist?(LOCK_FILE_NAME)
+      File.readlines(LOCK_FILE_NAME).map(&:chomp)
+    else
+      []
+    end
+  end
+
+  def self.dump(ary)
+    contents = ary.map(&:to_s).uniq.sort.join("\n") + "\n"
+    File.write(LOCK_FILE_NAME, contents)
+  end
+end
+
+class ConstantLeakError < StandardError
+end
+
+class ConstantsLeakCheckerAction
+  def initialize(save)
+    @save = save
+    @check = !save
+    @constants_locked = ConstantsLockFile.load
+    @exclude_patterns = MSpecScript.get(:toplevel_constants_excludes) || []
+  end
+
+  def register
+    MSpec.register :start, self
+    MSpec.register :before, self
+    MSpec.register :after, self
+    MSpec.register :finish, self
+  end
+
+  def start
+    @constants_start = constants_now
+  end
+
+  def before(state)
+    @constants_before = constants_now
+  end
+
+  def after(state)
+    constants = remove_excludes(constants_now - @constants_before - @constants_locked)
+
+    if @check && !constants.empty?
+      MSpec.protect 'Constants leak check' do
+        raise ConstantLeakError, "Top level constants leaked: #{constants.join(', ')}"
+      end
+    end
+  end
+
+  def finish
+    constants = remove_excludes(constants_now - @constants_start - @constants_locked)
+
+    if @save
+      ConstantsLockFile.dump(@constants_locked + constants)
+    end
+
+    if @check && !constants.empty?
+      MSpec.protect 'Global constants leak check' do
+        raise ConstantLeakError, "Top level constants leaked in the whole test suite: #{constants.join(', ')}"
+      end
+    end
+  end
+
+  private
+
+  def constants_now
+    Object.constants.map(&:to_s)
+  end
+
+  def remove_excludes(constants)
+    constants.reject { |name|
+      @exclude_patterns.any? { |pattern| pattern === name }
+    }
+  end
+end