From 299cb5e1d1b68fe842a109298d6cda0a2fa1cffd Mon Sep 17 00:00:00 2001
From: Adnan Maolood <me@adnano.co>
Date: Tue, 27 Sep 2022 08:13:11 -0400
Subject: [PATCH] templates: Fix base template block customization

Previously, kiln would error out if any blocks defined in the base
template were not defined in page or index templates. Instead, make
customizing base template blocks optional. This also allows base
template blocks to have a default value.
---
 templates.go | 67 ++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 47 insertions(+), 20 deletions(-)

diff --git a/templates.go b/templates.go
index 6314c28..ff00ee7 100644
--- a/templates.go
+++ b/templates.go
@@ -9,50 +9,69 @@ import (
 	pathpkg "path"
 	"strings"
 	"text/template"
-	"text/template/parse"
 )
 
 // Template represents a template.
 type Template interface {
-	AddParseTree(*parse.Tree) error
+	Clone() (Template, error)
+	AddTemplates(Template) error
 	Execute(io.Writer, interface{}) error
-	Tree() *parse.Tree
 }
 
 type textTemplate struct {
 	tmpl *template.Template
 }
 
-func (t textTemplate) AddParseTree(tree *parse.Tree) error {
-	_, err := t.tmpl.AddParseTree(t.tmpl.Name(), tree)
-	return err
+func (t textTemplate) Clone() (Template, error) {
+	clone, err := t.tmpl.Clone()
+	return textTemplate{clone}, err
+}
+
+func (t textTemplate) AddTemplates(other Template) error {
+	otherTmpl := other.(textTemplate).tmpl
+	for _, def := range otherTmpl.Templates() {
+		if def.Name() == otherTmpl.Name() {
+			continue
+		}
+		_, err := t.tmpl.AddParseTree(def.Name(), def.Tree)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func (t textTemplate) Execute(w io.Writer, data interface{}) error {
 	return t.tmpl.Execute(w, data)
 }
 
-func (t textTemplate) Tree() *parse.Tree {
-	return t.tmpl.Tree
-}
-
 type htmlTemplate struct {
 	tmpl *htemplate.Template
 }
 
-func (t htmlTemplate) AddParseTree(tree *parse.Tree) error {
-	_, err := t.tmpl.AddParseTree(t.tmpl.Name(), tree)
-	return err
+func (t htmlTemplate) Clone() (Template, error) {
+	clone, err := t.tmpl.Clone()
+	return htmlTemplate{clone}, err
+}
+
+func (t htmlTemplate) AddTemplates(other Template) error {
+	otherTmpl := other.(htmlTemplate).tmpl
+	for _, def := range otherTmpl.Templates() {
+		if def.Name() == otherTmpl.Name() {
+			continue
+		}
+		_, err := t.tmpl.AddParseTree(def.Name(), def.Tree)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func (t htmlTemplate) Execute(w io.Writer, data interface{}) error {
 	return t.tmpl.Execute(w, data)
 }
 
-func (t htmlTemplate) Tree() *parse.Tree {
-	return t.tmpl.Tree
-}
-
 // Templates contains site templates.
 type Templates struct {
 	tmpls map[string]Template
@@ -129,12 +148,20 @@ func (t *Templates) Load(dir string, exts []string) error {
 		if _, ok := extsMap[ext]; !ok {
 			continue
 		}
-		base := pathpkg.Join(pathpkg.Dir(path), "base"+ext)
-		if tmpl, ok := t.tmpls[base]; ok {
-			err := t.tmpls[path].AddParseTree(tmpl.Tree())
+		basePath := pathpkg.Join(pathpkg.Dir(path), "base"+ext)
+		if path == basePath {
+			continue
+		}
+		if base, ok := t.tmpls[basePath]; ok {
+			tmpl, err := base.Clone()
 			if err != nil {
 				return err
 			}
+			// Load customized template definitions
+			if err := tmpl.AddTemplates(t.tmpls[path]); err != nil {
+				return err
+			}
+			t.tmpls[path] = tmpl
 		}
 	}
 	return nil