text/template: The ability to output an io.Reader #25160
Description
Having the ability to templatize and concatenate multiple streams through a template would be highly useful. One can think of this as a generalization of the functionality provided by MultiReader, TeeReader, etc, except we'd have the ability to store stubs in files, and have more granular control of intermediate text and formatting.
For example, I'd like to be able to write something similar to the following:
r := // some predefined io.Reader...
t, _ := template.New("").Parse(`
<html>
<head>
<meta charset="UTF-8"><meta name="viewport" content="width=device-width, maximum-scale=1.0">
<link href="/static/blog.css" rel="stylesheet">
</head>
<body>
{{ . }}
</body>
</html>
`)
t.Execute(os.Stdout, r)Currently, I have a workaround using channels, however the overhead of channel communication doesn't make it worth using.
copyReader := func(c chan<- string, r io.Reader) {
p := make([]byte, 100)
for {
n, err := r.Read(p)
c <- string(p[:n])
if err != nil {
close(c)
break
}
}
}
r := // some predefined io.Reader...
t, _ := template.New("").Parse(`
<html>
<head>
<meta charset="UTF-8"><meta name="viewport" content="width=device-width, maximum-scale=1.0">
<link href="/static/blog.css" rel="stylesheet">
</head>
<body>
{{range .}}{{.}}{{end}}
</body>
</html>
`)
c := make(chan string)
go copyReader(c, r)
t.Execute(os.Stdout, c)