Refactor render system (#32492)

There were too many patches to the Render system, it's really difficult
to make further improvements.

This PR clears the legacy problems and fix TODOs.

1. Rename `RenderContext.Type` to `RenderContext.MarkupType` to clarify
its usage.
2. Use `ContentMode` to replace `meta["mode"]` and `IsWiki`, to clarify
the rendering behaviors.
3. Use "wiki" mode instead of "mode=gfm + wiki=true"
4. Merge `renderByType` and `renderByFile`
5. Add more comments

----

The problem of "mode=document": in many cases it is not set, so many
non-comment places use comment's hard line break incorrectly

modules/markup/render.go

@@ -5,11 +5,9 @@ package markup
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"io"
 	"net/url"
-	"path/filepath"
 	"strings"
 	"sync"
 
@@ -29,15 +27,44 @@ const (
 	RenderMetaAsTable   RenderMetaMode = "table"
 )
 
+type RenderContentMode string
+
+const (
+	RenderContentAsDefault RenderContentMode = "" // empty means "default", no special handling, maybe just a simple "document"
+	RenderContentAsComment RenderContentMode = "comment"
+	RenderContentAsTitle   RenderContentMode = "title"
+	RenderContentAsWiki    RenderContentMode = "wiki"
+)
+
+var RenderBehaviorForTesting struct {
+	// Markdown line break rendering has 2 default behaviors:
+	// * Use hard: replace "\n" with "<br>" for comments, setting.Markdown.EnableHardLineBreakInComments=true
+	// * Keep soft: "\n" for non-comments (a.k.a. documents), setting.Markdown.EnableHardLineBreakInDocuments=false
+	// In history, there was a mess:
+	// * The behavior was controlled by `Metas["mode"] != "document",
+	// * However, many places render the content without setting "mode" in Metas, all these places used comment line break setting incorrectly
+	ForceHardLineBreak bool
+
+	// Gitea will emit some internal attributes for various purposes, these attributes don't affect rendering.
+	// But there are too many hard-coded test cases, to avoid changing all of them again and again, we can disable emitting these internal attributes.
+	DisableInternalAttributes bool
+}
+
 // RenderContext represents a render context
 type RenderContext struct {
-	Ctx              context.Context
-	RelativePath     string // relative path from tree root of the branch
-	Type             string
-	IsWiki           bool
-	Links            Links
-	Metas            map[string]string // user, repo, mode(comment/document)
-	DefaultLink      string
+	Ctx          context.Context
+	RelativePath string // relative path from tree root of the branch
+
+	// eg: "orgmode", "asciicast", "console"
+	// for file mode, it could be left as empty, and will be detected by file extension in RelativePath
+	MarkupType string
+
+	// what the content will be used for: eg: for comment or for wiki? or just render a file?
+	ContentMode RenderContentMode
+
+	Links            Links             // special link references for rendering, especially when there is a branch/tree path
+	Metas            map[string]string // user&repo, format&style&regexp (for external issue pattern), teams&org (for mention), BranchNameSubURL(for iframe&asciicast)
+	DefaultLink      string            // TODO: need to figure out
 	GitRepo          *git.Repository
 	Repo             gitrepo.Repository
 	ShaExistCache    map[string]bool
@@ -77,12 +104,29 @@ func (ctx *RenderContext) AddCancel(fn func()) {
 
 // Render renders markup file to HTML with all specific handling stuff.
 func Render(ctx *RenderContext, input io.Reader, output io.Writer) error {
-	if ctx.Type != "" {
-		return renderByType(ctx, input, output)
-	} else if ctx.RelativePath != "" {
-		return renderFile(ctx, input, output)
+	if ctx.MarkupType == "" && ctx.RelativePath != "" {
+		ctx.MarkupType = DetectMarkupTypeByFileName(ctx.RelativePath)
+		if ctx.MarkupType == "" {
+			return util.NewInvalidArgumentErrorf("unsupported file to render: %q", ctx.RelativePath)
+		}
 	}
-	return errors.New("render options both filename and type missing")
+
+	renderer := renderers[ctx.MarkupType]
+	if renderer == nil {
+		return util.NewInvalidArgumentErrorf("unsupported markup type: %q", ctx.MarkupType)
+	}
+
+	if ctx.RelativePath != "" {
+		if externalRender, ok := renderer.(ExternalRenderer); ok && externalRender.DisplayInIFrame() {
+			if !ctx.InStandalonePage {
+				// for an external "DisplayInIFrame" render, it could only output its content in a standalone page
+				// otherwise, a <iframe> should be outputted to embed the external rendered page
+				return renderIFrame(ctx, output)
+			}
+		}
+	}
+
+	return render(ctx, renderer, input, output)
 }
 
 // RenderString renders Markup string to HTML with all specific handling stuff and return string
@@ -170,42 +214,6 @@ func render(ctx *RenderContext, renderer Renderer, input io.Reader, output io.Wr
 	return err
 }
 
-func renderByType(ctx *RenderContext, input io.Reader, output io.Writer) error {
-	if renderer, ok := renderers[ctx.Type]; ok {
-		return render(ctx, renderer, input, output)
-	}
-	return fmt.Errorf("unsupported render type: %s", ctx.Type)
-}
-
-// ErrUnsupportedRenderExtension represents the error when extension doesn't supported to render
-type ErrUnsupportedRenderExtension struct {
-	Extension string
-}
-
-func IsErrUnsupportedRenderExtension(err error) bool {
-	_, ok := err.(ErrUnsupportedRenderExtension)
-	return ok
-}
-
-func (err ErrUnsupportedRenderExtension) Error() string {
-	return fmt.Sprintf("Unsupported render extension: %s", err.Extension)
-}
-
-func renderFile(ctx *RenderContext, input io.Reader, output io.Writer) error {
-	extension := strings.ToLower(filepath.Ext(ctx.RelativePath))
-	if renderer, ok := extRenderers[extension]; ok {
-		if r, ok := renderer.(ExternalRenderer); ok && r.DisplayInIFrame() {
-			if !ctx.InStandalonePage {
-				// for an external render, it could only output its content in a standalone page
-				// otherwise, a <iframe> should be outputted to embed the external rendered page
-				return renderIFrame(ctx, output)
-			}
-		}
-		return render(ctx, renderer, input, output)
-	}
-	return ErrUnsupportedRenderExtension{extension}
-}
-
 // Init initializes the render global variables
 func Init(ph *ProcessorHelper) {
 	if ph != nil {