15-recover_chroma

README

Gophercises - 15 - Development Panic/Recover Middleware with Chroma

Problem

• https://github.com/gophercises/recover_chroma
• https://gophercises.com/exercises/recover_chroma

Solution

• main.go: Code and panic highlight

Lessons Learned

http.Error Only Support Plaintext

When doing http.Error the result will be sent as text and not text/html.

Use fmt.Fprintf(w, ...) instead.

Chroma

Already familiar because it's used in Hugo.

quick.Highlight sacrifices control but does things quickly:

quick.Highlight(os.Stdout, someSourceCode, "go", "html", "monokai")

For more control use formatter.Format(w io.Writer, s *Style, it Iterator):

// Highlighter is a more hands-on version of QuickHighlighter and comes with
// lines highlight support.
func Highlighter(fileName, source, style string, lineno int) (string, error) {
	// If styleText does not match any style, it will return "swapoff."
	// So we check if we entered "swapoff" and if not, we will change it to
	// "solarized-dark."
	st := styles.Get(style)
	if st.Name == "swapoff" && style != "swapoff" {
		st = styles.Get("solarized-dark")
	}

	// While we already know we are looking at Go code, we are going to
	// Chroma's lexer.Analyze to get the lexer based on extension.
	// https://github.com/alecthomas/chroma#identifying-the-language
	lexer := lexers.Match(fileName)
	// lexer is nil if no match could be found.
	if lexer == nil {
		// So we use the Analyse function.
		lexer = lexers.Analyse(source)
	}
	// Default to Go, if neither process detected a lexer.
	if lexer == nil {
		lexer = lexers.Get("go")
	}

	// Create the range variable for highlighting line numbers.
	// It's of type [][2]int.
	hl := [][2]int{[2]int{lineno, lineno}}
	// We are only highlighting one line so both items in the [2]int array
	// are the same. If we wanted to highlight a range, we would have used
	// start and finish line numbers.

	// Create a customized html.Formatter.
	// We can also get rid of the 8 tab space now.
	formatter := html.New(html.Standalone(), html.WithLineNumbers(),
		html.HighlightLines(hl), html.TabWidth(4))

	// Get iterator.
	it, err := lexer.Tokenise(nil, source)
	if err != nil {
		return "", err
	}

	var b bytes.Buffer
	wri := bufio.NewWriter(&b)

	if err := formatter.Format(wri, st, it); err != nil {
		return "", err
	}

	return b.String(), nil
}

Documentation

Overview

debug.go contains all the code for exercise 15.

This file is from the previous exercise with an extra line in main to add the debug handler. The debug handler and all other functions are in debug.go