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Use a text template when printing a "pretty error"
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@xyproto
xyproto committed Jun 26, 2024
1 parent 71f0cdc commit 498e5d8
Showing 1 changed file with 72 additions and 72 deletions.
144 changes: 72 additions & 72 deletions engine/prettyerror.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,15 +5,58 @@ import (
"net/http"
"strconv"
"strings"
"text/template"
)

const (
// Highlight of errors in the code
preHighlight = "<font style='color: red !important'>"
postHighlight = "</font>"

// HTML template for the error page
htmlTemplate = `<!doctype html>
<html>
<head>
<title>{{.Title}}</title>
<style>
body {
background-color: #f0f0f0;
color: #0b0b0b;
font-family: Lato,'Trebuchet MS',Helvetica,sans-serif;
font-weight: 300;
margin: 3.5em;
font-size: 1.3em;
}
h1 {
color: #101010;
}
div {
margin-bottom: 35pt;
}
#right {
text-align: right;
}
#wrap {
white-space: pre-wrap;
}
</style>
</head>
<body>
<div style="font-size: 3em; font-weight: bold;">{{.Title}}</div>
Contents of {{.Filename}}:
<div>
<pre><code>{{.Code}}</code></pre>
</div>
Error message:
<div>
<pre id="wrap"><code style="color: #A00000;">{{.ErrorMessage}}</code></pre>
</div>
<div id="right">{{.VersionString}}</div>
</body>
</html>`
)

// Given a lowercase string for the language, return an approprite error page title
// Given a lowercase string for the language, return an appropriate error page title
func errorPageTitle(lang string) string {
switch lang {
case "":
Expand All @@ -27,24 +70,19 @@ func errorPageTitle(lang string) string {
case "jsx":
return "JSX Error"
default:
// string.Title(lang) was used here before, but staticcheck recommends against it
return lang + " Error"
}
}

// PrettyError serves an informative error page to the user
// Takes a ResponseWriter, title (can be empty), filename, filebytes, errormessage and
// programming/scripting/template language (i.e. "lua". Can be empty).
func (ac *Config) PrettyError(w http.ResponseWriter, req *http.Request, filename string, filebytes []byte, errormessage, lang string) {
// HTTP status
// w.WriteHeader(http.StatusInternalServerError)
w.WriteHeader(http.StatusOK)

// HTTP content type
w.Header().Add("Content-Type", "text/html;charset=utf-8")

var (
// If there is code to be displayed
code string
err error
)
Expand All @@ -54,112 +92,74 @@ func (ac *Config) PrettyError(w http.ResponseWriter, req *http.Request, filename

if len(filebytes) > 0 {
if lang == "lua" {
// If the first line of the error message has two colons, see if the second field is a number
fields := strings.SplitN(errormessage, ":", 3)
if len(fields) > 2 {
// Extract the line number from the error message, if possible
numberfield := fields[1]
if strings.Contains(numberfield, "(") {
numberfield = strings.Split(numberfield, "(")[0]
}
linenr, err = strconv.Atoi(numberfield)
// Subtract one to make it a slice index instead of human-friendly line number
linenr--
// Set linenumber to -1 if the conversion failed
if err != nil {
linenr = -1
}
}
} else if lang == "amber" {
// If the error contains "- Line: ", extract the line number
if strings.Contains(errormessage, "- Line: ") {
fields := strings.SplitN(errormessage, "- Line: ", 2)
if strings.Contains(fields[1], ",") {
numberfields := strings.SplitN(fields[1], ",", 2)
linenr, err = strconv.Atoi(strings.TrimSpace(numberfields[0]))
// Subtract one to make it a slice index instead of human-friendly line number
linenr--
// Set linenumber to -1 if the conversion failed
if err != nil {
linenr = -1
}
}
}
}

// Escape any HTML in the code, so that the pretty printer is not confused
filebytes = bytes.ReplaceAll(filebytes, []byte("<"), []byte("&lt;"))

// Modify the line that is to be highlighted
bytelines := bytes.Split(filebytes, []byte("\n"))
if (linenr >= 0) && (linenr < len(bytelines)) {
bytelines[linenr] = []byte(preHighlight + string(bytelines[linenr]) + postHighlight)
}

// Build a string from the bytelines slice
code = string(bytes.Join(bytelines, []byte("\n")))
}

// Set an appropriate title
title := errorPageTitle(lang)

// Set the highlight class
langclass := lang

// Turn off highlighting for some languages
switch lang {
case "", "amber", "gcss":
langclass = "nohighlight"
data := struct {
Title string
Filename string
Code string
ErrorMessage string
VersionString string
}{
Title: title,
Filename: filename,
Code: code,
ErrorMessage: strings.TrimSpace(errormessage),
VersionString: ac.versionString,
}

// Highlighting for the error message
errorclass := "json" // "nohighlight"

// Inform the user of the error
htmldata := []byte(`<!doctype html>
<html>
<head>
<title>` + title + `</title>
<style>
body {
background-color: #f0f0f0;
color: #0b0b0b;
font-family: Lato,'Trebuchet MS',Helvetica,sans-serif;
font-weight: 300;
margin: 3.5em;
font-size: 1.3em;
}
h1 {
color: #101010;
}
div {
margin-bottom: 35pt;
}
#right {
text-align: right;
}
#wrap {
white-space: pre-wrap;
}
</style>
</head>
<body>
<div style="font-size: 3em; font-weight: bold;">` + title + `</div>
Contents of ` + filename + `:
<div>
<pre><code class="` + langclass + `">` + code + `</code></pre>
</div>
Error message:
<div>
<pre id="wrap"><code style="color: #A00000;" class="` + errorclass + `">` + strings.TrimSpace(errormessage) + `</code></pre>
</div>
<div id="right">` + ac.versionString + `</div>
`)
tmpl, err := template.New("errorPage").Parse(htmlTemplate)
if err != nil {
http.Error(w, "Internal Server Error", http.StatusInternalServerError)
return
}

if ac.autoRefresh {
// Insert JavaScript for refreshing the page into the generated HTML
htmldata = ac.InsertAutoRefresh(req, htmldata)
var htmlbuf bytes.Buffer
if err := tmpl.Execute(&htmlbuf, data); err != nil {
http.Error(w, "Internal Server Error", http.StatusInternalServerError)
return
}
w.Write(ac.InsertAutoRefresh(req, htmlbuf.Bytes()))
return
}

w.Write(htmldata)
if err := tmpl.Execute(w, data); err != nil {
http.Error(w, "Internal Server Error", http.StatusInternalServerError)
return
}
}

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