fix: address no-template-associated type of error

Signed-off-by: Jesse Simpson <jesse.simpson36@gmail.com>

pkg/engine/engine.go

@@ -41,6 +41,10 @@ var execErrFmt = regexp.MustCompile(`^template: (?P<templateName>(?U).+): execut
 // > "template: %s: %s"
 var execErrFmtWithoutTemplate = regexp.MustCompile(`^template: (?P<templateName>(?U).+): (?P<errMsg>.*)(?P<nextErr>( template:.*)?)$`)
 
+// taken from https://cs.opensource.google/go/go/+/refs/tags/go1.23.6:src/text/template/exec.go;l=191
+// > "template: no template %q associated with template %q"
+var execErrNoTemplateAssociated = regexp.MustCompile(`^template: no template (?P<location>.*) associated with template (?P<functionName>(.*)?)$`)
+
 // Engine is an implementation of the Helm rendering implementation for templates.
 type Engine struct {
 	// If strict is enabled, template rendering will fail if a template references
@@ -345,7 +349,17 @@ type TraceableError struct {
 }
 
 func (t TraceableError) String() string {
-	return t.location + "\n  " + t.executedFunction + "\n    " + t.message + "\n"
+	var errorString strings.Builder
+	if t.location != "" {
+		fmt.Fprintf(&errorString, "%s\n  ", t.location)
+	}
+	if t.executedFunction != "" {
+		fmt.Fprintf(&errorString, "%s\n    ", t.executedFunction)
+	}
+	if t.message != "" {
+		fmt.Fprintf(&errorString, "%s\n", t.message)
+	}
+	return errorString.String()
 }
 
 // reformatExecErrorMsg takes an error message for template rendering and formats it into a formatted
@@ -394,6 +408,10 @@ func reformatExecErrorMsg(filename string, err error) error {
 				location: templateName,
 				message:  errMsg,
 			}
+		} else if matches := execErrNoTemplateAssociated.FindStringSubmatch(current.Error()); matches != nil {
+			traceable = TraceableError{
+				message: current.Error(),
+			}
 		} else {
 			return err
 		}

pkg/engine/engine_test.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"text/template"
 
 	"github.com/stretchr/testify/assert"
 
@@ -1336,6 +1337,40 @@ NestedHelperFunctions/charts/common/templates/_helpers_2.tpl:1:50
 	assert.Equal(t, expectedErrorMessage, err.Error())
 }
 
+func TestMultilineNoTemplateAssociatedError(t *testing.T) {
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{Name: "multiline"},
+		Templates: []*chart.File{
+			{Name: "templates/svc.yaml", Data: []byte(
+				`name: {{ include "nested_helper.name" . }}`,
+			)},
+			{Name: "templates/test.yaml", Data: []byte(
+				`{{ toYaml .Values }}`,
+			)},
+			{Name: "charts/common/templates/_helpers_2.tpl", Data: []byte(
+				`{{ toYaml .Values }}`,
+			)},
+		},
+	}
+
+	expectedErrorMessage := `multiline/templates/svc.yaml:1:9
+  executing "multiline/templates/svc.yaml" at <include "nested_helper.name" .>:
+    error calling include:
+template: no template "nested_helper.name" associated with template "gotpl"
+`
+
+	v := chartutil.Values{}
+
+	val, _ := chartutil.CoalesceValues(c, v)
+	vals := map[string]interface{}{
+		"Values": val.AsMap(),
+	}
+	_, err := Render(c, vals)
+
+	assert.NotNil(t, err)
+	assert.Equal(t, expectedErrorMessage, err.Error())
+}
+
 func TestRenderCustomTemplateFuncs(t *testing.T) {
 	// Create a chart with two templates that use custom functions
 	c := &chart.Chart{