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.

Matthew Holt committed Jan 11, 2021 at 13:49 UTC 14f50d9dfb6c0da0da636829175a37b1864d23cf

1 file changed +24 -2

modules/caddyhttp/templates/tplcontext.go

+24 -2

@@ -153,7 +153,9 @@ func (c templateContext) executeTemplateInBuffer(tplName string, buf *bytes.Buff

153 "splitFrontMatter": c.funcSplitFrontMatter,

154 "listFiles": c.funcListFiles,

155 "env": c.funcEnv,

156 - "placeholder": c.placeholder,

156 + "placeholder": c.funcPlaceholder,

157 + "fileExists": c.funcFileExists,

158 + "httpError": c.funcHTTPError,

159 })

160

161 parsedTpl, err := tpl.Parse(buf.String())

@@ -166,7 +168,7 @@ func (c templateContext) executeTemplateInBuffer(tplName string, buf *bytes.Buff

168 return parsedTpl.Execute(buf, c)

169 }

170

169 -func (c templateContext) placeholder(name string) string {

171 +func (c templateContext) funcPlaceholder(name string) string {

172 repl := c.Req.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)

173 value, _ := repl.GetString(name)

174 return value

@@ -323,6 +325,26 @@ func (c templateContext) funcListFiles(name string) ([]string, error) {

325 return names, nil

326 }

327

328 +// funcFileExists returns true if filename can be opened successfully.

329 +func (c templateContext) funcFileExists(filename string) (bool, error) {

330 + if c.Root == nil {

331 + return false, fmt.Errorf("root file system not specified")

332 + }

333 + file, err := c.Root.Open(filename)

334 + if err == nil {

335 + file.Close()

336 + return true, nil

337 + }

338 + return false, nil

339 +}

340 +

341 +// funcHTTPError returns a structured HTTP handler error. EXPERIMENTAL.

342 +// TODO: Requires https://github.com/golang/go/issues/34201 to be fixed.

343 +// Example usage might be: `{{if not (fileExists $includeFile)}}{{httpError 404}}{{end}}`

344 +func (c templateContext) funcHTTPError(statusCode int) (bool, error) {

345 + return false, caddyhttp.Error(statusCode, nil)

346 +}

347 +

348 // tplWrappedHeader wraps niladic functions so that they

349 // can be used in templates. (Template functions must

350 // return a value.)