Support DieOnBadParams option, add tests

template_nest.go

@@ -111,12 +111,12 @@ func New(opts Option) (*TemplateNest, error) {
 func (nest *TemplateNest) index(filePath string) (TemplateFileIndex, error) {
 	contents, err := ioutil.ReadFile(filePath)
 	if err != nil {
-		return TemplateFileIndex{}, fmt.Errorf("Error reading file (`%s`): %w", filePath, err)
+		return TemplateFileIndex{}, fmt.Errorf("error reading file (`%s`): %w", filePath, err)
 	}
 	// Capture last modified time
 	fileInfo, err := os.Stat(filePath)
 	if err != nil {
-		return TemplateFileIndex{}, fmt.Errorf("Error getting file (`%s`) info: %w", filePath, err)
+		return TemplateFileIndex{}, fmt.Errorf("error getting file (`%s`) info: %w", filePath, err)
 	}
 
 	variableNames := make(map[string]struct{})
@@ -205,12 +205,16 @@ func (nest *TemplateNest) Render(toRender interface{}) (string, error) {
 	case Hash:
 		tLabel, ok := v[nest.option.NameLabel]
 		if !ok {
-			return "", fmt.Errorf("missing template label: %s", nest.option.NameLabel)
+			return "", fmt.Errorf(
+				"encountered hash with no name label (name label: `%s`)", nest.option.NameLabel,
+			)
 		}
 
 		tName, ok := tLabel.(string)
 		if !ok {
-			return "", fmt.Errorf("invalid template label: %+v", tLabel)
+			return "", fmt.Errorf(
+				"encountered hash with invalid name label type: %+v", tLabel,
+			)
 		}
 
 		tFile := nest.getTemplateFilePath(tName)
@@ -225,11 +229,24 @@ func (nest *TemplateNest) Render(toRender interface{}) (string, error) {
 		if !exists || fileInfo.ModTime().After(tIndex.LastModified) {
 			newIndex, err := nest.index(tFile)
 			if err != nil {
-				return "", fmt.Errorf("File index failed: %w", err)
+				return "", fmt.Errorf("file index failed: %w", err)
 			}
 			tIndex = newIndex
 		}
 
+		if nest.option.DieOnBadParams {
+			for k, _ := range v {
+				// If a variable in template hash is not present in template
+				// file and it's not the template label then it's a bad param.
+				_, exists := tIndex.VariableNames[k]
+				if !exists && k != nest.option.NameLabel {
+					return "", fmt.Errorf(
+						"bad params in template hash, variable not present in template file: `%s`", k,
+					)
+				}
+			}
+		}
+
 		rendered := tIndex.Contents
 		for i := len(tIndex.Variables) - 1; i >= 0; i-- {
 			variable := tIndex.Variables[i]
@@ -257,6 +274,6 @@ func (nest *TemplateNest) Render(toRender interface{}) (string, error) {
 		return strings.TrimSpace(rendered), nil
 
 	default:
-		return "", fmt.Errorf("Unsupported template type: %+v", v)
+		return "", fmt.Errorf("unsupported template hash value type: %+v", v)
 	}
 }

tests/02_die_on_bad_params_test.go

@@ -0,0 +1,72 @@
+package tests
+
+import (
+	"git.virtual.blue/tomgracey/template-nest-go"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestDieOnPageWithBadParams(t *testing.T) {
+	nest, err := templatenest.New(templatenest.Option{
+		TemplateDir:    "templates",
+		DieOnBadParams: true,
+	})
+	if err != nil {
+		t.Fatalf("Failed to initialize TemplateNest: %+v", err)
+	}
+
+	page := templatenest.Hash{
+		"TEMPLATE":         "00-simple-page",
+		"variable":         "Simple Variable",
+		"simple_component": "Simple Component",
+		"a_bad_param":      "Bad Param",
+	}
+
+	_, err = nest.Render(page)
+	if assert.NotNil(t, err) {
+		expected := "bad params in template hash, variable not present in template file: `a_bad_param`"
+		assert.Equal(t, expected, err.Error())
+	}
+}
+
+func TestDieOnPageWithBadParams01(t *testing.T) {
+	nest, err := templatenest.New(templatenest.Option{
+		TemplateDir:    "templates",
+		DieOnBadParams: true,
+	})
+	if err != nil {
+		t.Fatalf("Failed to initialize TemplateNest: %+v", err)
+	}
+
+	page := templatenest.Hash{
+		"TEMPLATE":    "00-simple-page",
+		"variable":    "Simple Variable",
+		"a_bad_param": "Bad Param",
+	}
+
+	_, err = nest.Render(page)
+	if assert.NotNil(t, err) {
+		expected := "bad params in template hash, variable not present in template file: `a_bad_param`"
+		assert.Equal(t, expected, err.Error())
+	}
+}
+
+func TestLiveOnPageWithBadParams(t *testing.T) {
+	nest, err := templatenest.New(templatenest.Option{
+		TemplateDir:    "templates",
+		DieOnBadParams: false,
+	})
+	if err != nil {
+		t.Fatalf("Failed to initialize TemplateNest: %+v", err)
+	}
+
+	page := templatenest.Hash{
+		"TEMPLATE":         "00-simple-page",
+		"variable":         "Simple Variable",
+		"simple_component": "Simple Component",
+		"a_bad_param":      "Bad Param",
+	}
+
+	_, err = nest.Render(page)
+	assert.Nil(t, err)
+}