tpl: Add proper file context to template parse errors

Fixes #13604

Author: bep

Diff for: tpl/templates/templates_integration_test.go

@@ -17,6 +17,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	qt "github.com/frankban/quicktest"
 	"github.com/gohugoio/hugo/hugolib"
 )
 
@@ -229,3 +230,35 @@ layouts/section/section.html
 	b := hugolib.Test(t, files)
 	b.AssertFileContent("public/mysection/index.html", "layouts/section/section.html")
 }
+
+func TestErrorMessageParseError(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+-- layouts/home.html --
+Line 1.
+Line 2. {{ foo }} <- this func does not exist.
+Line 3.
+`
+
+	b, err := hugolib.TestE(t, files)
+	b.Assert(err, qt.IsNotNil)
+	b.Assert(err.Error(), qt.Contains, filepath.FromSlash(`"/layouts/home.html:2:1": parse of template failed: template: home.html:2: function "foo" not defined`))
+}
+
+func TestErrorMessageExecuteError(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+-- layouts/home.html --
+Line 1.
+Line 2. {{ .Foo }} <- this method does not exist.
+Line 3.
+`
+
+	b, err := hugolib.TestE(t, files)
+	b.Assert(err, qt.IsNotNil)
+	b.Assert(err.Error(), qt.Contains, filepath.FromSlash(` "/layouts/home.html:2:11": execute of template failed`))
+}

Diff for: tpl/tplimpl/templates.go

@@ -44,7 +44,16 @@ var embeddedTemplatesAliases = map[string][]string{
 	"_shortcodes/twitter.html": {"_shortcodes/tweet.html"},
 }
 
-func (t *templateNamespace) parseTemplate(ti *TemplInfo) error {
+func (s *TemplateStore) parseTemplate(ti *TemplInfo) error {
+	err := s.tns.doParseTemplate(ti)
+	if err != nil {
+		return s.addFileContext(ti, "parse of template failed", err)
+	}
+
+	return err
+}
+
+func (t *templateNamespace) doParseTemplate(ti *TemplInfo) error {
 	if !ti.noBaseOf || ti.category == CategoryBaseof {
 		// Delay parsing until we have the base template.
 		return nil

Diff for: tpl/tplimpl/templatestore.go

@@ -495,7 +495,7 @@ func (t *TemplateStore) ExecuteWithContext(ctx context.Context, ti *TemplInfo, w
 
 	execErr := t.storeSite.executer.ExecuteWithContext(ctx, ti, wr, data)
 	if execErr != nil {
-		return t.addFileContext(ti, execErr)
+		return t.addFileContext(ti, "execute of template failed", execErr)
 	}
 	return nil
 }
@@ -822,7 +822,7 @@ func (t *TemplateStore) addDeferredTemplate(owner *TemplInfo, name string, n *pa
 	return nil
 }
 
-func (s *TemplateStore) addFileContext(ti *TemplInfo, inerr error) error {
+func (s *TemplateStore) addFileContext(ti *TemplInfo, what string, inerr error) error {
 	if ti.Fi == nil {
 		return inerr
 	}
@@ -854,25 +854,27 @@ func (s *TemplateStore) addFileContext(ti *TemplInfo, inerr error) error {
 		fe := herrors.NewFileErrorFromName(inErr, fi.Meta().Filename)
 		fe.UpdateContent(f, lineMatcher)
 
-		if !fe.ErrorContext().Position.IsValid() {
-			return inErr, false
-		}
-		return fe, true
+		return fe, fe.ErrorContext().Position.IsValid()
 	}
 
-	inerr = fmt.Errorf("execute of template failed: %w", inerr)
+	inerr = fmt.Errorf("%s: %w", what, inerr)
 
-	if err, ok := checkFilename(ti.Fi, inerr); ok {
-		return err
+	var (
+		currentErr error
+		ok         bool
+	)
+
+	if currentErr, ok = checkFilename(ti.Fi, inerr); ok {
+		return currentErr
 	}
 
 	if ti.base != nil {
-		if err, ok := checkFilename(ti.base.Fi, inerr); ok {
-			return err
+		if currentErr, ok = checkFilename(ti.base.Fi, inerr); ok {
+			return currentErr
 		}
 	}
 
-	return inerr
+	return currentErr
 }
 
 func (s *TemplateStore) extractIdentifiers(line string) []string {
@@ -1389,7 +1391,7 @@ func (s *TemplateStore) parseTemplates() error {
 				if vv.state == processingStateTransformed {
 					continue
 				}
-				if err := s.tns.parseTemplate(vv); err != nil {
+				if err := s.parseTemplate(vv); err != nil {
 					return err
 				}
 			}
@@ -1409,7 +1411,7 @@ func (s *TemplateStore) parseTemplates() error {
 						// The regular expression used to detect if a template needs a base template has some
 						// rare false positives. Assume we don't need one.
 						vv.noBaseOf = true
-						if err := s.tns.parseTemplate(vv); err != nil {
+						if err := s.parseTemplate(vv); err != nil {
 							return err
 						}
 						continue
@@ -1438,7 +1440,7 @@ func (s *TemplateStore) parseTemplates() error {
 				if vvv.state == processingStateTransformed {
 					continue
 				}
-				if err := s.tns.parseTemplate(vvv); err != nil {
+				if err := s.parseTemplate(vvv); err != nil {
 					return err
 				}
 			}