Don't panic when regex doesn't compile

Instead, print a warning and discard the invalid rule.

customHeaders.go

@@ -26,10 +26,20 @@ type HeaderConfig struct {
 	CompiledRegex *regexp.Regexp
 }
 
-func (config *HeaderConfig) Init() {
+func (config *HeaderConfig) Init() (ok bool) {
 	if len(config.Regex) > 0 {
-		config.CompiledRegex = regexp.MustCompile(config.Regex)
+		regex, err := regexp.Compile(config.Regex)
+
+		if err != nil {
+			fmt.Println("WARNING: Ignoring rule with regex error:", err)
+			fmt.Println("")
+			return
+		}
+		config.CompiledRegex = regex
 	}
+
+	ok = true
+	return
 }
 
 func (config *HeaderConfig) UsesRegex() bool {
@@ -42,7 +52,7 @@ type HeaderDefiniton struct {
 	Value string `json:"value"`
 }
 
-var headerConfigs *HeaderConfigArray
+var headerConfigs HeaderConfigArray
 
 func fileExists(filename string) bool {
 	info, err := os.Stat(filename)
@@ -52,7 +62,7 @@ func fileExists(filename string) bool {
 	return !info.IsDir()
 }
 
-func logHeaderConfig(config *HeaderConfig) {
+func logHeaderConfig(config HeaderConfig) {
 	if config.UsesRegex() {
 		fmt.Println("Regex: " + config.Regex)
 	} else {
@@ -74,7 +84,7 @@ func initHeaderConfig(headerConfigPath string) bool {
 	if fileExists(headerConfigPath) {
 		jsonFile, err := os.Open(headerConfigPath)
 		if err != nil {
-			fmt.Println("Cant't read header config file. Error:")
+			fmt.Println("Can't read header config file. Error:")
 			fmt.Println(err)
 		} else {
 			byteValue, _ := ioutil.ReadAll(jsonFile)
@@ -83,12 +93,22 @@ func initHeaderConfig(headerConfigPath string) bool {
 
 			if len(headerConfigs.Configs) > 0 {
 				headerConfigValid = true
+
+				// Only keep valid config entries.
+				keepers := make([]HeaderConfig, 0)
+				for _, configEntry := range headerConfigs.Configs {
+					ok := configEntry.Init()
+					if ok {
+						keepers = append(keepers, configEntry)
+					}
+				}
+
+				headerConfigs.Configs = keepers
+
+				// Print the config entries that are kept.
 				fmt.Println("Found header config file. Rules:")
 				fmt.Println("------------------------------")
-
-				for i := 0; i < len(headerConfigs.Configs); i++ {
-					configEntry := &headerConfigs.Configs[i]
-					configEntry.Init()
+				for _, configEntry := range headerConfigs.Configs {
 					logHeaderConfig(configEntry)
 				}
 			} else {

customHeaders_test.go

@@ -0,0 +1,39 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestHeaderConfigWithValidRegex(t *testing.T) {
+	assert := assert.New(t)
+	config := HeaderConfig{Regex: "/$"}
+
+	ok := config.Init()
+	assert.True(ok)
+	assert.NotNil(config.CompiledRegex)
+	assert.True(config.UsesRegex())
+}
+
+func TestHeaderConfigWithInvalidRegex(t *testing.T) {
+	assert := assert.New(t)
+	config := HeaderConfig{Regex: "["}
+
+	ok := config.Init()
+	assert.False(ok)
+	assert.Nil(config.CompiledRegex)
+}
+
+func TestHeaderConfigWithoutRegex(t *testing.T) {
+	assert := assert.New(t)
+	config := HeaderConfig{
+		Path:          "/page-data",
+		FileExtension: "json",
+	}
+
+	ok := config.Init()
+	assert.True(ok)
+	assert.Nil(config.CompiledRegex)
+	assert.False(config.UsesRegex())
+}

go.mod

@@ -1,3 +1,5 @@
 module github.com/PierreZ/goStatic
 
 go 1.16
+
+require github.com/stretchr/testify v1.7.0

go.sum

@@ -0,0 +1,11 @@
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=