templates: Add fileExists and httpError template actions

The httpError function isn't particularly useful until https://github.com/golang/go/issues/34201 is fixed in the Go standard lib.

1 files changed, 24 insertions, 2 deletions

diff --git a/modules/caddyhttp/templates/tplcontext.go b/modules/caddyhttp/templates/tplcontext.go
index 8bdaeec7e..1212ee20f 100644
--- a/modules/caddyhttp/templates/tplcontext.go
+++ b/modules/caddyhttp/templates/tplcontext.go
@@ -153,7 +153,9 @@ func (c templateContext) executeTemplateInBuffer(tplName string, buf *bytes.Buff
 		"splitFrontMatter": c.funcSplitFrontMatter,
 		"listFiles":        c.funcListFiles,
 		"env":              c.funcEnv,
-		"placeholder":      c.placeholder,
+		"placeholder":      c.funcPlaceholder,
+		"fileExists":       c.funcFileExists,
+		"httpError":        c.funcHTTPError,
 	})
 
 	parsedTpl, err := tpl.Parse(buf.String())
@@ -166,7 +168,7 @@ func (c templateContext) executeTemplateInBuffer(tplName string, buf *bytes.Buff
 	return parsedTpl.Execute(buf, c)
 }
 
-func (c templateContext) placeholder(name string) string {
+func (c templateContext) funcPlaceholder(name string) string {
 	repl := c.Req.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 	value, _ := repl.GetString(name)
 	return value
@@ -323,6 +325,26 @@ func (c templateContext) funcListFiles(name string) ([]string, error) {
 	return names, nil
 }
 
+// funcFileExists returns true if filename can be opened successfully.
+func (c templateContext) funcFileExists(filename string) (bool, error) {
+	if c.Root == nil {
+		return false, fmt.Errorf("root file system not specified")
+	}
+	file, err := c.Root.Open(filename)
+	if err == nil {
+		file.Close()
+		return true, nil
+	}
+	return false, nil
+}
+
+// funcHTTPError returns a structured HTTP handler error. EXPERIMENTAL.
+// TODO: Requires https://github.com/golang/go/issues/34201 to be fixed.
+// Example usage might be: `{{if not (fileExists $includeFile)}}{{httpError 404}}{{end}}`
+func (c templateContext) funcHTTPError(statusCode int) (bool, error) {
+	return false, caddyhttp.Error(statusCode, nil)
+}
+
 // tplWrappedHeader wraps niladic functions so that they
 // can be used in templates. (Template functions must
 // return a value.)