Merge pull request #88 from victorxw/87-fix-regexp-cache-race

fix race in `reDict` when reading from regexp cache

Author: fredbi

rexp.go

@@ -26,24 +26,24 @@ var (
 )
 
 func compileRegexp(pattern string) (*re.Regexp, error) {
+	cacheMutex.Lock()
+	defer cacheMutex.Unlock()
 	// Save repeated regexp compilation
 	if reDict[pattern] != nil {
 		return reDict[pattern], nil
 	}
 	var err error
-	cacheMutex.Lock()
 	reDict[pattern], err = re.Compile(pattern)
-	cacheMutex.Unlock()
 	return reDict[pattern], err
 }
 
 func mustCompileRegexp(pattern string) *re.Regexp {
+	cacheMutex.Lock()
+	defer cacheMutex.Unlock()
 	// Save repeated regexp compilation, with panic on error
 	if reDict[pattern] != nil {
 		return reDict[pattern]
 	}
-	defer cacheMutex.Unlock()
-	cacheMutex.Lock()
 	reDict[pattern] = re.MustCompile(pattern)
 	return reDict[pattern]
 }

rexp_test.go

@@ -57,3 +57,50 @@ func Test_mustCompileRegexp(t *testing.T) {
 
 	assert.Panics(t, testPanic)
 }
+
+func TestRace_compileRegexp(t *testing.T) {
+	vrex := new(re.Regexp)
+
+	patterns := []string{
+		".*TestRegexp1.*",
+		".*TestRegexp2.*",
+		".*TestRegexp3.*",
+	}
+
+	comp := func(pattern string) {
+		rex, err := compileRegexp(pattern)
+		assert.NoError(t, err)
+		assert.NotNil(t, rex)
+		assert.IsType(t, vrex, rex)
+	}
+
+	for i := 0; i < 20; i++ {
+		t.Run(patterns[i%3], func(t *testing.T) {
+			t.Parallel()
+			comp(patterns[i%3])
+		})
+	}
+}
+
+func TestRace_mustCompileRegexp(t *testing.T) {
+	vrex := new(re.Regexp)
+
+	patterns := []string{
+		".*TestRegexp1.*",
+		".*TestRegexp2.*",
+		".*TestRegexp3.*",
+	}
+
+	comp := func(pattern string) {
+		rex := mustCompileRegexp(pattern)
+		assert.NotNil(t, rex)
+		assert.IsType(t, vrex, rex)
+	}
+
+	for i := 0; i < 20; i++ {
+		t.Run(patterns[i%3], func(t *testing.T) {
+			t.Parallel()
+			comp(patterns[i%3])
+		})
+	}
+}