Support defaults, add tests

template_nest.go

@@ -23,6 +23,9 @@ type Option struct {
 	CommentDelimiters     [2]string // Used in conjunction with ShowLabels, if HTML then use '<!--', '-->'
 	FixedIndent           bool      // Intended to improve readability when inspecting nested templates
 	TokenEscapeChar       string    // Escapes a token delimiter, i.e. if set to '\' then variables that have '\' prefix won't be replaced
+	DefaultsNamespaceChar string
+	Defaults              Hash // Provide a hash of default values that are substituted if template hash does not provide a value
+	defaultsFlat          Hash
 }
 
 type TemplateNest struct {
@@ -73,6 +76,14 @@ func New(opts Option) (*TemplateNest, error) {
 	if opts.TemplateExtension == "" {
 		opts.TemplateExtension = "html"
 	}
+	if opts.DefaultsNamespaceChar == "" {
+		opts.DefaultsNamespaceChar = "."
+	}
+	if opts.Defaults == nil {
+		opts.Defaults = make(map[string]interface{})
+	}
+
+	opts.defaultsFlat = FlattenMap(opts.Defaults, "", opts.DefaultsNamespaceChar)
 
 	// Initialize TemplateNest with the final options.
 	nest := &TemplateNest{
@@ -115,6 +126,28 @@ func New(opts Option) (*TemplateNest, error) {
 	return nest, nil
 }
 
+// FlattenMap flattens a nested map[string]interface{} into a flat map with
+// dot-separated keys.
+func FlattenMap(input Hash, parentKey string, separator string) Hash {
+	result := make(map[string]interface{})
+	for key, value := range input {
+		fullKey := key
+		if parentKey != "" {
+			fullKey = parentKey + separator + key
+		}
+
+		// Check if the value is a nested map
+		if nestedMap, ok := value.(Hash); ok {
+			for k, v := range FlattenMap(nestedMap, fullKey, separator) {
+				result[k] = v
+			}
+		} else {
+			result[fullKey] = value
+		}
+	}
+	return result
+}
+
 func (nest *TemplateNest) index(filePath string) (TemplateFileIndex, error) {
 	contents, err := ioutil.ReadFile(filePath)
 	if err != nil {
@@ -303,7 +336,14 @@ func (nest *TemplateNest) Render(toRender interface{}) (string, error) {
 			// with an empty string.
 			replacement := ""
 
-			if value, exists := v[variable.Name]; exists {
+			value, exists := v[variable.Name]
+			defaultValue, defaultExists := nest.option.defaultsFlat[variable.Name]
+
+			if exists || defaultExists {
+				if !exists {
+					value = defaultValue
+				}
+
 				subRender, err := nest.Render(value)
 				if err != nil {
 					return "", err

tests/08_defaults_test.go

@@ -0,0 +1,51 @@
+package tests
+
+import (
+	"git.virtual.blue/tomgracey/template-nest-go"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestRenderWithDefaults(t *testing.T) {
+	nest, err := templatenest.New(templatenest.Option{
+		TemplateDir: "templates",
+		Defaults: templatenest.Hash{
+			"variable": "Simple Variable",
+			"space": templatenest.Hash{
+				"inside": "A variable inside a space.",
+			},
+		},
+	})
+	if err != nil {
+		t.Fatalf("Failed to initialize TemplateNest: %+v", err)
+	}
+
+	page := templatenest.Hash{
+		"TEMPLATE": "00-simple-page",
+		"simple_component": []templatenest.Hash{
+			templatenest.Hash{
+				"TEMPLATE": "01-simple-component",
+				"variable": "Simple Variable in Simple Component",
+			},
+		},
+	}
+
+	outputPage := templatenest.Hash{"TEMPLATE": "output/01-simple-page"}
+
+	assert.Equal(
+		t,
+		nest.MustRender(outputPage),
+		nest.MustRender(page),
+		"Rendered output does not match expected output",
+	)
+
+	spacePage := templatenest.Hash{"TEMPLATE": "03-namespace-page"}
+	spaceOutputPage := templatenest.Hash{"TEMPLATE": "output/11-namespace-page"}
+
+	assert.Equal(
+		t,
+		nest.MustRender(spaceOutputPage),
+		nest.MustRender(spacePage),
+		"Rendered output does not match expected output",
+	)
+}