refactor: small tweak to template rendering helpers (#182)

Author: mccutchen

examples/custom-instrumentation/go.mod

@@ -1,6 +1,6 @@
 module httpbin-instrumentation
 
-go 1.22
+go 1.22.0
 
 require (
 	github.com/DataDog/datadog-go v4.8.3+incompatible

go.mod

@@ -1,3 +1,3 @@
 module github.com/mccutchen/go-httpbin/v2
 
-go 1.22
+go 1.22.0

httpbin/httpbin.go

@@ -99,9 +99,10 @@ func New(opts ...OptionFunc) *HTTPBin {
 	}
 
 	// pre-compute some configuration values and pre-render templates
+	tmplData := struct{ Prefix string }{Prefix: h.prefix}
+	h.indexHTML = mustRenderTemplate("index.html.tmpl", tmplData)
+	h.formsPostHTML = mustRenderTemplate("forms-post.html.tmpl", tmplData)
 	h.statusSpecialCases = createSpecialCases(h.prefix)
-	h.indexHTML = h.mustRenderTemplate("index.html.tmpl")
-	h.formsPostHTML = h.mustRenderTemplate("forms-post.html.tmpl")
 
 	// compute max Server-Sent Event count based on max request size and rough
 	// estimate of a single event's size on the wire

httpbin/static_assets.go

@@ -24,14 +24,10 @@ func mustStaticAsset(name string) []byte {
 	return b
 }
 
-func (h *HTTPBin) mustRenderTemplate(name string) []byte {
-	t, err := template.New(name).Parse(string(mustStaticAsset(name)))
-	if err != nil {
-		panic(err)
-	}
+func mustRenderTemplate(name string, data any) []byte {
+	t := template.Must(template.New(name).Parse(string(mustStaticAsset(name)))).Option("missingkey=error")
 	var buf bytes.Buffer
-	ctx := struct{ Prefix string }{Prefix: h.prefix}
-	if err := t.Execute(&buf, ctx); err != nil {
+	if err := t.Execute(&buf, data); err != nil {
 		panic(err)
 	}
 	return buf.Bytes()

httpbin/static_assets_test.go

@@ -2,7 +2,8 @@ package httpbin
 
 import "testing"
 
-// Silly test just to satisfy coverage
+// Silly tests just to increase code coverage scores
+
 func TestMustStaticAsset(t *testing.T) {
 	defer func() {
 		// recover from panic if one occured. Set err to nil otherwise.
@@ -12,3 +13,25 @@ func TestMustStaticAsset(t *testing.T) {
 	}()
 	mustStaticAsset("xxxyyyzzz")
 }
+
+func TestMustRenderTemplate(t *testing.T) {
+	t.Run("invalid template name", func(t *testing.T) {
+		defer func() {
+			// recover from panic if one occured. Set err to nil otherwise.
+			if err := recover(); err == nil {
+				t.Fatalf("expected to recover from panic, got nil")
+			}
+		}()
+		mustRenderTemplate("xxxyyyzzz", nil)
+	})
+
+	t.Run("invalid template data", func(t *testing.T) {
+		defer func() {
+			// recover from panic if one occured. Set err to nil otherwise.
+			if err := recover(); err == nil {
+				t.Fatalf("expected to recover from panic, got nil")
+			}
+		}()
+		mustRenderTemplate("index.html.tmpl", nil)
+	})
+}