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forgejo/modules/markup/markdown/markdown.go
Gergely Nagy b594188623
Restore compatibility with the legacy GitHub callout syntax
Although GitHub removed support for the legacy callout syntax, we don't
have to! Restore this support via another AST transformer.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
2024-02-17 18:35:45 +01:00

303 lines
7.9 KiB
Go

// Copyright 2014 The Gogs Authors. All rights reserved.
// Copyright 2018 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT
package markdown
import (
"fmt"
"io"
"strings"
"sync"
"code.gitea.io/gitea/modules/log"
"code.gitea.io/gitea/modules/markup"
"code.gitea.io/gitea/modules/markup/common"
"code.gitea.io/gitea/modules/markup/markdown/callout"
"code.gitea.io/gitea/modules/markup/markdown/math"
"code.gitea.io/gitea/modules/setting"
giteautil "code.gitea.io/gitea/modules/util"
chromahtml "github.com/alecthomas/chroma/v2/formatters/html"
"github.com/yuin/goldmark"
highlighting "github.com/yuin/goldmark-highlighting/v2"
meta "github.com/yuin/goldmark-meta"
"github.com/yuin/goldmark/extension"
"github.com/yuin/goldmark/parser"
"github.com/yuin/goldmark/renderer"
"github.com/yuin/goldmark/renderer/html"
"github.com/yuin/goldmark/util"
)
var (
specMarkdown goldmark.Markdown
specMarkdownOnce sync.Once
)
var (
renderContextKey = parser.NewContextKey()
renderConfigKey = parser.NewContextKey()
)
type limitWriter struct {
w io.Writer
sum int64
limit int64
}
// Write implements the standard Write interface:
func (l *limitWriter) Write(data []byte) (int, error) {
leftToWrite := l.limit - l.sum
if leftToWrite < int64(len(data)) {
n, err := l.w.Write(data[:leftToWrite])
l.sum += int64(n)
if err != nil {
return n, err
}
return n, fmt.Errorf("rendered content too large - truncating render")
}
n, err := l.w.Write(data)
l.sum += int64(n)
return n, err
}
// newParserContext creates a parser.Context with the render context set
func newParserContext(ctx *markup.RenderContext) parser.Context {
pc := parser.NewContext(parser.WithIDs(newPrefixedIDs()))
pc.Set(renderContextKey, ctx)
return pc
}
// SpecializedMarkdown sets up the Gitea specific markdown extensions
func SpecializedMarkdown() goldmark.Markdown {
specMarkdownOnce.Do(func() {
specMarkdown = goldmark.New(
goldmark.WithExtensions(
extension.NewTable(
extension.WithTableCellAlignMethod(extension.TableCellAlignAttribute)),
extension.Strikethrough,
extension.TaskList,
extension.DefinitionList,
common.FootnoteExtension,
highlighting.NewHighlighting(
highlighting.WithFormatOptions(
chromahtml.WithClasses(true),
chromahtml.PreventSurroundingPre(true),
),
highlighting.WithWrapperRenderer(func(w util.BufWriter, c highlighting.CodeBlockContext, entering bool) {
if entering {
language, _ := c.Language()
if language == nil {
language = []byte("text")
}
languageStr := string(language)
preClasses := []string{"code-block"}
if languageStr == "mermaid" || languageStr == "math" {
preClasses = append(preClasses, "is-loading")
}
_, err := w.WriteString(`<pre class="` + strings.Join(preClasses, " ") + `">`)
if err != nil {
return
}
// include language-x class as part of commonmark spec
_, err = w.WriteString(`<code class="chroma language-` + string(language) + `">`)
if err != nil {
return
}
} else {
_, err := w.WriteString("</code></pre>")
if err != nil {
return
}
}
}),
),
math.NewExtension(
math.Enabled(setting.Markdown.EnableMath),
),
meta.Meta,
),
goldmark.WithParserOptions(
parser.WithAttribute(),
parser.WithAutoHeadingID(),
parser.WithASTTransformers(
util.Prioritized(&callout.GitHubLegacyCalloutTransformer{}, 8000),
util.Prioritized(&callout.GitHubCalloutTransformer{}, 9000),
util.Prioritized(&ASTTransformer{}, 10000),
),
),
goldmark.WithRendererOptions(
html.WithUnsafe(),
),
)
// Override the original Tasklist renderer!
specMarkdown.Renderer().AddOptions(
renderer.WithNodeRenderers(
util.Prioritized(callout.NewGitHubCalloutHTMLRenderer(), 10),
util.Prioritized(NewHTMLRenderer(), 10),
),
)
})
return specMarkdown
}
// actualRender renders Markdown to HTML without handling special links.
func actualRender(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
converter := SpecializedMarkdown()
lw := &limitWriter{
w: output,
limit: setting.UI.MaxDisplayFileSize * 3,
}
// FIXME: should we include a timeout to abort the renderer if it takes too long?
defer func() {
err := recover()
if err == nil {
return
}
log.Warn("Unable to render markdown due to panic in goldmark: %v", err)
if log.IsDebug() {
log.Debug("Panic in markdown: %v\n%s", err, log.Stack(2))
}
}()
// FIXME: Don't read all to memory, but goldmark doesn't support
pc := newParserContext(ctx)
buf, err := io.ReadAll(input)
if err != nil {
log.Error("Unable to ReadAll: %v", err)
return err
}
buf = giteautil.NormalizeEOL(buf)
// Preserve original length.
bufWithMetadataLength := len(buf)
rc := &RenderConfig{
Meta: renderMetaModeFromString(string(ctx.RenderMetaAs)),
Icon: "table",
Lang: "",
}
buf, _ = ExtractMetadataBytes(buf, rc)
metaLength := bufWithMetadataLength - len(buf)
if metaLength < 0 {
metaLength = 0
}
rc.metaLength = metaLength
pc.Set(renderConfigKey, rc)
if err := converter.Convert(buf, lw, parser.WithContext(pc)); err != nil {
log.Error("Unable to render: %v", err)
return err
}
return nil
}
// Note: The output of this method must get sanitized.
func render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
defer func() {
err := recover()
if err == nil {
return
}
log.Warn("Unable to render markdown due to panic in goldmark - will return raw bytes")
if log.IsDebug() {
log.Debug("Panic in markdown: %v\n%s", err, log.Stack(2))
}
_, err = io.Copy(output, input)
if err != nil {
log.Error("io.Copy failed: %v", err)
}
}()
return actualRender(ctx, input, output)
}
// MarkupName describes markup's name
var MarkupName = "markdown"
func init() {
markup.RegisterRenderer(Renderer{})
}
// Renderer implements markup.Renderer
type Renderer struct{}
var _ markup.PostProcessRenderer = (*Renderer)(nil)
// Name implements markup.Renderer
func (Renderer) Name() string {
return MarkupName
}
// NeedPostProcess implements markup.PostProcessRenderer
func (Renderer) NeedPostProcess() bool { return true }
// Extensions implements markup.Renderer
func (Renderer) Extensions() []string {
return setting.Markdown.FileExtensions
}
// SanitizerRules implements markup.Renderer
func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
return []setting.MarkupSanitizerRule{}
}
// Render implements markup.Renderer
func (Renderer) Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
return render(ctx, input, output)
}
// Render renders Markdown to HTML with all specific handling stuff.
func Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
if ctx.Type == "" {
ctx.Type = MarkupName
}
return markup.Render(ctx, input, output)
}
// RenderString renders Markdown string to HTML with all specific handling stuff and return string
func RenderString(ctx *markup.RenderContext, content string) (string, error) {
var buf strings.Builder
if err := Render(ctx, strings.NewReader(content), &buf); err != nil {
return "", err
}
return buf.String(), nil
}
// RenderRaw renders Markdown to HTML without handling special links.
func RenderRaw(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
rd, wr := io.Pipe()
defer func() {
_ = rd.Close()
_ = wr.Close()
}()
go func() {
if err := render(ctx, input, wr); err != nil {
_ = wr.CloseWithError(err)
return
}
_ = wr.Close()
}()
return markup.SanitizeReader(rd, "", output)
}
// RenderRawString renders Markdown to HTML without handling special links and return string
func RenderRawString(ctx *markup.RenderContext, content string) (string, error) {
var buf strings.Builder
if err := RenderRaw(ctx, strings.NewReader(content), &buf); err != nil {
return "", err
}
return buf.String(), nil
}