ext/coverage/coverage.c: add Coverage.enabled?

* ext/coverage/coverage.c (rb_coverage_running): add to quickly
check if coverage is enabled.  patched by Burke Libbey <burke AT
libbey.me> in [ruby-core:81726].  [Feature #13667]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59716 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/coverage/coverage.c

@@ -75,6 +75,20 @@ rb_coverage_result(VALUE klass)
     return ncoverages;
 }
 
+/*
+ *  call-seq:
+ *     Coverage.running?  => bool
+ *
+ * Returns true if coverage stats are currently being collected (after
+ * Coverage.start call, but before Coverage.result call)
+ */
+static VALUE
+rb_coverage_running(VALUE klass)
+{
+    VALUE coverages = rb_get_coverages();
+    return RTEST(coverages) ? Qtrue : Qfalse;
+}
+
 /* Coverage provides coverage measurement feature for Ruby.
  * This feature is experimental, so these APIs may be changed in future.
  *
@@ -115,4 +129,5 @@ Init_coverage(void)
     rb_define_module_function(rb_mCoverage, "start", rb_coverage_start, 0);
     rb_define_module_function(rb_mCoverage, "result", rb_coverage_result, 0);
     rb_define_module_function(rb_mCoverage, "peek_result", rb_coverage_peek_result, 0);
+    rb_define_module_function(rb_mCoverage, "running?", rb_coverage_running, 0);
 }

test/coverage/test_coverage.rb

@@ -23,6 +23,16 @@ class TestCoverage < Test::Unit::TestCase
     end
   end
 
+  def test_coverage_running?
+    refute Coverage.running?
+    Coverage.start
+    assert Coverage.running?
+    Coverage.peek_result
+    assert Coverage.running?
+    Coverage.result
+    refute Coverage.running?
+  end
+
   def test_coverage_snapshot
     loaded_features = $".dup