Merge pull request #58 from hairyhenderson/55-default-region

Adding ability to provide default for ec2region function

README.md

@@ -245,14 +245,23 @@ us-east-1
 
 #### `ec2region`
 
-Queries AWS to get the region. Returns `unknown` if it can't be determined for some reason.
+Queries AWS to get the region. An optional default can be provided, or returns
+`unknown` if it can't be determined for some reason.
 
 ##### Example
 
+_In EC2_
 ```console
 $ echo '{{ ec2region }}' | ./gomplate
 us-east-1
 ```
+_Not in EC2_
+```console
+$ echo '{{ ec2region }}' | ./gomplate
+unknown
+$ echo '{{ ec2region "foo" }}' | ./gomplate
+foo
+```
 
 #### `ec2tag`
 

aws/ec2meta.go

@@ -71,10 +71,15 @@ func (e *Ec2Meta) Dynamic(key string, def ...string) string {
 }
 
 // Region -
-func (e *Ec2Meta) Region() string {
-	doc := e.Dynamic("instance-identity/document", `{"region":"unknown"}`)
+func (e *Ec2Meta) Region(def ...string) string {
+	defaultRegion := returnDefault(def)
+	if defaultRegion == "" {
+		defaultRegion = "unknown"
+	}
+
+	doc := e.Dynamic("instance-identity/document", `{"region":"`+defaultRegion+`"}`)
 	obj := &InstanceDocument{
-		Region: "unknown",
+		Region: defaultRegion,
 	}
 	err := json.Unmarshal([]byte(doc), &obj)
 	if err != nil {

aws/ec2meta_test.go

@@ -45,6 +45,13 @@ func TestRegion_NoRegion(t *testing.T) {
 	assert.Equal(t, "unknown", ec2meta.Region())
 }
 
+func TestRegion_NoRegionWithDefault(t *testing.T) {
+	server, ec2meta := MockServer(200, "{}")
+	defer server.Close()
+
+	assert.Equal(t, "foo", ec2meta.Region("foo"))
+}
+
 func TestRegion_KnownRegion(t *testing.T) {
 	server, ec2meta := MockServer(200, `{"region":"us-east-1"}`)
 	defer server.Close()