Check Drive HTML Templates

Let’s have a look at how one can do it in phases: We begin with the next take a look at that tries to compile the template. In Go we use the usual html/template bundle.

Go

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    _ = templ
  }

In Java we use moustache
as a result of it is rather straightforward to make use of; free marker both
Pace are different frequent choices.

Java

  @Check
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
  }

If we run this take a look at, it can fail, as a result of the index.tmpl the file doesn’t exist. So we create it, with the damaged HTML above. Now the take a look at ought to cross.

Then we create a mannequin for the template to make use of. The app manages a to-do checklist and we will create a minimal mannequin for demonstration functions.

Go

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    mannequin := todo.NewList()
    _ = templ
    _ = mannequin
  }

Java

  @Check
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
      var mannequin = new TodoList();
  }

Now we render the template, saving the ends in a byte buffer (Go) or as a String (Java).

Go

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    mannequin := todo.NewList()
    var buf bytes.Buffer
    err := templ.Execute(&buf, mannequin)
    if err != nil {
      panic(err)
    }
  }

Java

  @Check
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
      var mannequin = new TodoList();
  
      var html = template.execute(mannequin);
  }

At this level we wish parse the HTML and we anticipate to see an error, as a result of in our damaged HTML there’s a div component that’s closed by a p component. There’s an HTML parser within the Go customary library, but it surely’s too forgiving: if we run it on our damaged HTML, we do not get an error. Fortuitously, the Go customary library additionally has an XML parser that may be configured to parse HTML (because of this stack overflow reply)

Go

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    mannequin := todo.NewList()
    
    // render the template right into a buffer
    var buf bytes.Buffer
    err := templ.Execute(&buf, mannequin)
    if err != nil {
      panic(err)
    }
  
    // verify that the template will be parsed as (lenient) XML
    decoder := xml.NewDecoder(bytes.NewReader(buf.Bytes()))
    decoder.Strict = false
    decoder.AutoClose = xml.HTMLAutoClose
    decoder.Entity = xml.HTMLEntity
    for {
      _, err := decoder.Token()
      swap err {
      case io.EOF:
        return // We're accomplished, it is legitimate!
      case nil:
        // do nothing
      default:
        t.Fatalf("Error parsing html: %s", err)
      }
    }
  }

fountain

This code configures the HTML parser to have the right degree of leniency for HTML after which parses the HTML token by token. In reality, we see the error message we needed:

--- FAIL: Test_wellFormedHtml (0.00s)
    index_template_test.go:61: Error parsing html: XML syntax error on line 4: surprising finish component 

In Java, a flexible library to make use of is jsopa:

Java

  @Check
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
      var mannequin = new TodoList();
  
      var html = template.execute(mannequin);
  
      var parser = Parser.htmlParser().setTrackErrors(10);
      Jsoup.parse(html, "", parser);
      assertThat(parser.getErrors()).isEmpty();
  }

fountain

And we see it fail:

java.lang.AssertionError: 
Anticipating empty however was:<(<1:13>: Sudden EndTag token () when in state (InBody),

Success! Now if we copy TodoMVC template content material to our index.tmpl file, the take a look at passes.

The proof, nonetheless, is just too detailed: we extract two auxiliary features to make clear the intent of the proof and procure

Go

  func Test_wellFormedHtml(t *testing.T) {
    mannequin := todo.NewList()
  
    buf := renderTemplate("index.tmpl", mannequin)
  
    assertWellFormedHtml(t, buf)
  }

fountain

Java

  @Check
  void indexIsSoundHtml() {
      var mannequin = new TodoList();
  
      var html = renderTemplate("/index.tmpl", mannequin);
  
      assertSoundHtml(html);
  }

fountain