Add support to render template from string

Signed-off-by: Ivan Kolodiazhnyi <[email protected]>

Author: e0ne

pkg/render/render.go

@@ -64,7 +64,7 @@ func RenderDir(manifestDir string, d *RenderData) ([]*unstructured.Unstructured,
 			return nil
 		}
 
-		objs, err := RenderTemplate(path, d)
+		objs, err := RenderFileTemplate(path, d)
 		if err != nil {
 			return err
 		}
@@ -77,10 +77,14 @@ func RenderDir(manifestDir string, d *RenderData) ([]*unstructured.Unstructured,
 	return out, nil
 }
 
-// RenderTemplate reads, renders, and attempts to parse a yaml or
+func RenderTemplate(template string, d *RenderData) (*bytes.Buffer, error) {
+	return renderTemplate(template, d)
+}
+
+// RenderFileTemplate reads, renders, and attempts to parse a yaml or
 // json file representing one or more k8s api objects
-func RenderTemplate(path string, d *RenderData) ([]*unstructured.Unstructured, error) {
-	rendered, err := renderTemplate(path, d)
+func RenderFileTemplate(path string, d *RenderData) ([]*unstructured.Unstructured, error) {
+	rendered, err := renderFileTemplate(path, d)
 	if err != nil {
 		return nil, err
 	}
@@ -112,8 +116,9 @@ func RenderTemplate(path string, d *RenderData) ([]*unstructured.Unstructured, e
 	return out, nil
 }
 
-func renderTemplate(path string, d *RenderData) (*bytes.Buffer, error) {
-	tmpl := template.New(path).Option("missingkey=error")
+func renderTemplate(rawTemplate string, d *RenderData) (*bytes.Buffer, error) {
+
+	tmpl := template.New("template").Option("missingkey=error")
 	if d.Funcs != nil {
 		tmpl.Funcs(d.Funcs)
 	}
@@ -122,23 +127,28 @@ func renderTemplate(path string, d *RenderData) (*bytes.Buffer, error) {
 	tmpl.Funcs(template.FuncMap{"getOr": getOr, "isSet": isSet})
 	tmpl.Funcs(sprig.TxtFuncMap())
 
-	source, err := os.ReadFile(path)
-	if err != nil {
-		return nil, errors.Wrapf(err, "failed to read manifest %s", path)
-	}
-
-	if _, err := tmpl.Parse(string(source)); err != nil {
-		return nil, errors.Wrapf(err, "failed to parse manifest %s as template", path)
+	if _, err := tmpl.Parse(rawTemplate); err != nil {
+		return nil, errors.Wrapf(err, "failed to parse manifest %s as template", rawTemplate)
 	}
 
 	rendered := bytes.Buffer{}
 	if err := tmpl.Execute(&rendered, d.Data); err != nil {
-		return nil, errors.Wrapf(err, "failed to render manifest %s", path)
+		return nil, errors.Wrapf(err, "failed to render manifest %s", rawTemplate)
 	}
 
 	return &rendered, nil
 }
 
+func renderFileTemplate(path string, d *RenderData) (*bytes.Buffer, error) {
+
+	source, err := os.ReadFile(path)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to read manifest %s", path)
+	}
+
+	return renderTemplate(string(source[:]), d)
+}
+
 func formateDeviceList(devs []DeviceInfo) string {
 	out := ""
 	for _, dev := range devs {
@@ -232,7 +242,7 @@ func filterTemplates(toFilter map[string]string, path string, d *RenderData) err
 		}
 
 		// Render the template file
-		renderedData, err := renderTemplate(path, d)
+		renderedData, err := renderFileTemplate(path, d)
 		if err != nil {
 			return err
 		}

pkg/render/render_test.go

@@ -12,7 +12,7 @@ func TestRenderSimple(t *testing.T) {
 
 	d := MakeRenderData()
 
-	o1, err := RenderTemplate("testdata/manifests/simple.yaml", &d)
+	o1, err := RenderFileTemplate("testdata/manifests/simple.yaml", &d)
 	g.Expect(err).NotTo(HaveOccurred())
 
 	g.Expect(o1).To(HaveLen(1))
@@ -36,7 +36,7 @@ func TestRenderSimple(t *testing.T) {
 	g.Expect(o1[0].MarshalJSON()).To(MatchJSON(expected))
 
 	// test that json parses the same
-	o2, err := RenderTemplate("testdata/manifests/simple.json", &d)
+	o2, err := RenderFileTemplate("testdata/manifests/simple.json", &d)
 	g.Expect(err).NotTo(HaveOccurred())
 	g.Expect(o2).To(Equal(o1))
 }
@@ -47,7 +47,7 @@ func TestRenderMultiple(t *testing.T) {
 	p := "testdata/manifests/multiple.yaml"
 	d := MakeRenderData()
 
-	o, err := RenderTemplate(p, &d)
+	o, err := RenderFileTemplate(p, &d)
 	g.Expect(err).NotTo(HaveOccurred())
 
 	g.Expect(o).To(HaveLen(3))
@@ -64,19 +64,19 @@ func TestTemplate(t *testing.T) {
 
 	// Test that missing variables are detected
 	d := MakeRenderData()
-	_, err := RenderTemplate(p, &d)
+	_, err := RenderFileTemplate(p, &d)
 	g.Expect(err).To(HaveOccurred())
 	g.Expect(err.Error()).To(HaveSuffix(`function "fname" not defined`))
 
 	// Set expected function (but not variable)
 	d.Funcs["fname"] = func(s string) string { return "test-" + s }
-	_, err = RenderTemplate(p, &d)
+	_, err = RenderFileTemplate(p, &d)
 	g.Expect(err).To(HaveOccurred())
 	g.Expect(err.Error()).To(HaveSuffix(`has no entry for key "Namespace"`))
 
 	// now we can render
 	d.Data["Namespace"] = "myns"
-	o, err := RenderTemplate(p, &d)
+	o, err := RenderFileTemplate(p, &d)
 	g.Expect(err).NotTo(HaveOccurred())
 
 	g.Expect(o[0].GetName()).To(Equal("test-podname"))
@@ -95,7 +95,7 @@ func TestTemplateWithEmptyObject(t *testing.T) {
 
 	d := MakeRenderData()
 	d.Data["Enable"] = true
-	o, err := RenderTemplate(p, &d)
+	o, err := RenderFileTemplate(p, &d)
 	g.Expect(err).NotTo(HaveOccurred())
 
 	g.Expect(len(o)).To(Equal(2))