Support rendering OpenAPI spec

modules/markup/asciicast/asciicast.go

@@ -20,27 +20,23 @@ func init() {
 // See https://github.com/asciinema/asciinema/blob/develop/doc/asciicast-v2.md
 type Renderer struct{}
 
-// Name implements markup.Renderer
 func (Renderer) Name() string {
 	return "asciicast"
 }
 
-// Extensions implements markup.Renderer
-func (Renderer) Extensions() []string {
-	return []string{".cast"}
+func (Renderer) FileNamePatterns() []string {
+	return []string{"*.cast"}
 }
 
 const (
 	playerClassName = "asciinema-player-container"
 	playerSrcAttr   = "data-asciinema-player-src"
 )
 
-// SanitizerRules implements markup.Renderer
 func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return []setting.MarkupSanitizerRule{{Element: "div", AllowAttr: playerSrcAttr}}
 }
 
-// Render implements markup.Renderer
 func (Renderer) Render(ctx *markup.RenderContext, _ io.Reader, output io.Writer) error {
 	rawURL := fmt.Sprintf("%s/%s/%s/raw/%s/%s",
 		setting.AppSubURL,

modules/markup/console/console.go

@@ -20,29 +20,24 @@ func init() {
 	markup.RegisterRenderer(Renderer{})
 }
 
-// Renderer implements markup.Renderer
 type Renderer struct{}
 
 var _ markup.RendererContentDetector = (*Renderer)(nil)
 
-// Name implements markup.Renderer
 func (Renderer) Name() string {
 	return "console"
 }
 
-// Extensions implements markup.Renderer
-func (Renderer) Extensions() []string {
-	return []string{".sh-session"}
+func (Renderer) FileNamePatterns() []string {
+	return []string{"*.sh-session"}
 }
 
-// SanitizerRules implements markup.Renderer
 func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return []setting.MarkupSanitizerRule{
 		{Element: "span", AllowAttr: "class", Regexp: `^term-((fg[ix]?|bg)\d+|container)$`},
 	}
 }
 
-// CanRender implements markup.RendererContentDetector
 func (Renderer) CanRender(filename string, sniffedType typesniffer.SniffedType, prefetchBuf []byte) bool {
 	if !sniffedType.IsTextPlain() {
 		return false

modules/markup/csv/csv.go

@@ -20,20 +20,16 @@ func init() {
 	markup.RegisterRenderer(Renderer{})
 }
 
-// Renderer implements markup.Renderer for csv files
 type Renderer struct{}
 
-// Name implements markup.Renderer
 func (Renderer) Name() string {
 	return "csv"
 }
 
-// Extensions implements markup.Renderer
-func (Renderer) Extensions() []string {
-	return []string{".csv", ".tsv"}
+func (Renderer) FileNamePatterns() []string {
+	return []string{"*.csv", "*.tsv"}
 }
 
-// SanitizerRules implements markup.Renderer
 func (Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return []setting.MarkupSanitizerRule{
 		{Element: "table", AllowAttr: "class", Regexp: `^data-table$`},

modules/markup/external/external.go

@@ -21,10 +21,9 @@ import (
 
 // RegisterRenderers registers all supported third part renderers according settings
 func RegisterRenderers() {
+	markup.RegisterRenderer(&openAPIRenderer{})
 	for _, renderer := range setting.ExternalMarkupRenderers {
-		if renderer.Enabled && renderer.Command != "" && len(renderer.FileExtensions) > 0 {
-			markup.RegisterRenderer(&Renderer{renderer})
-		}
+		markup.RegisterRenderer(&Renderer{renderer})
 	}
 }
 
@@ -38,22 +37,18 @@ var (
 	_ markup.ExternalRenderer    = (*Renderer)(nil)
 )
 
-// Name returns the external tool name
 func (p *Renderer) Name() string {
 	return p.MarkupName
 }
 
-// NeedPostProcess implements markup.Renderer
 func (p *Renderer) NeedPostProcess() bool {
 	return p.MarkupRenderer.NeedPostProcess
 }
 
-// Extensions returns the supported extensions of the tool
-func (p *Renderer) Extensions() []string {
-	return p.FileExtensions
+func (p *Renderer) FileNamePatterns() []string {
+	return p.FilePatterns
 }
 
-// SanitizerRules implements markup.Renderer
 func (p *Renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return p.MarkupSanitizerRules
 }

modules/markup/external/openapi.go

@@ -0,0 +1,79 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package external
+
+import (
+	"fmt"
+	"html"
+	"io"
+
+	"code.gitea.io/gitea/modules/markup"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+)
+
+type openAPIRenderer struct{}
+
+var (
+	_ markup.PostProcessRenderer = (*openAPIRenderer)(nil)
+	_ markup.ExternalRenderer    = (*openAPIRenderer)(nil)
+)
+
+func (p *openAPIRenderer) Name() string {
+	return "openapi"
+}
+
+func (p *openAPIRenderer) NeedPostProcess() bool {
+	return false
+}
+
+func (p *openAPIRenderer) FileNamePatterns() []string {
+	return []string{
+		"openapi.yaml",
+		"openapi.yml",
+		"openapi.json",
+		"swagger.yaml",
+		"swagger.yml",
+		"swagger.json",
+	}
+}
+
+func (p *openAPIRenderer) SanitizerRules() []setting.MarkupSanitizerRule {
+	return nil
+}
+
+func (p *openAPIRenderer) GetExternalRendererOptions() (ret markup.ExternalRendererOptions) {
+	ret.SanitizerDisabled = true
+	ret.DisplayInIframe = true
+	ret.ContentSandbox = ""
+	return ret
+}
+
+func (p *openAPIRenderer) Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error {
+	content, err := util.ReadWithLimit(input, int(setting.UI.MaxDisplayFileSize))
+	if err != nil {
+		return err
+	}
+	// TODO: can extract this to a tmpl file later
+	_, err = io.WriteString(output, fmt.Sprintf(
+		`<!DOCTYPE html>
+<html>
+<head>
+	<meta name="viewport" content="width=device-width, initial-scale=1">
+	<link rel="stylesheet" href="%s/assets/css/swagger.css?v=%s">
+</head>
+<body>
+	<div id="swagger-ui"><textarea class="swagger-spec-content" data-spec-filename="%s">%s</textarea></div>
+	<script src="%s/assets/js/swagger.js?v=%s"></script>
+</body>
+</html>`,
+		setting.StaticURLPrefix,
+		setting.AssetVersion,
+		html.EscapeString(ctx.RenderOptions.RelativePath),
+		html.EscapeString(util.UnsafeBytesToString(content)),
+		setting.StaticURLPrefix,
+		setting.AssetVersion,
+	))
+	return err
+}

modules/markup/main_test.go

@@ -14,5 +14,7 @@ import (
 func TestMain(m *testing.M) {
 	setting.IsInTesting = true
 	markup.RenderBehaviorForTesting.DisableAdditionalAttributes = true
+	setting.Markdown.FileNamePatterns = []string{"*.md"}
+	markup.RefreshFileNamePatterns()
 	os.Exit(m.Run())
 }

modules/markup/markdown/markdown.go

@@ -240,30 +240,24 @@ 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
+func (Renderer) FileNamePatterns() []string {
+	return setting.Markdown.FileNamePatterns
 }
 
-// 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)
 }

modules/markup/orgmode/orgmode.go

@@ -31,20 +31,16 @@ var (
 	_ markup.PostProcessRenderer = (*renderer)(nil)
 )
 
-// Name implements markup.Renderer
 func (renderer) Name() string {
 	return "orgmode"
 }
 
-// NeedPostProcess implements markup.PostProcessRenderer
 func (renderer) NeedPostProcess() bool { return true }
 
-// Extensions implements markup.Renderer
-func (renderer) Extensions() []string {
-	return []string{".org"}
+func (renderer) FileNamePatterns() []string {
+	return []string{"*.org"}
 }
 
-// SanitizerRules implements markup.Renderer
 func (renderer) SanitizerRules() []setting.MarkupSanitizerRule {
 	return []setting.MarkupSanitizerRule{}
 }

modules/markup/render.go

@@ -4,6 +4,7 @@
 package markup
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"html/template"
@@ -16,6 +17,7 @@ import (
 	"code.gitea.io/gitea/modules/htmlutil"
 	"code.gitea.io/gitea/modules/markup/internal"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/typesniffer"
 	"code.gitea.io/gitea/modules/util"
 
 	"golang.org/x/sync/errgroup"
@@ -144,22 +146,29 @@ func (ctx *RenderContext) WithHelper(helper RenderHelper) *RenderContext {
 	return ctx
 }
 
-// FindRendererByContext finds renderer by RenderContext
-// TODO: it should be merged with other similar functions like GetRendererByFileName, DetectMarkupTypeByFileName, etc
-func FindRendererByContext(ctx *RenderContext) (Renderer, error) {
+func (ctx *RenderContext) DetectMarkupRenderer(prefetchBuf []byte) Renderer {
 	if ctx.RenderOptions.MarkupType == "" && ctx.RenderOptions.RelativePath != "" {
-		ctx.RenderOptions.MarkupType = DetectMarkupTypeByFileName(ctx.RenderOptions.RelativePath)
-		if ctx.RenderOptions.MarkupType == "" {
-			return nil, util.NewInvalidArgumentErrorf("unsupported file to render: %q", ctx.RenderOptions.RelativePath)
+		var sniffedType typesniffer.SniffedType
+		if len(prefetchBuf) > 0 {
+			sniffedType = typesniffer.DetectContentType(prefetchBuf)
 		}
+		ctx.RenderOptions.MarkupType = DetectRendererTypeByPrefetch(ctx.RenderOptions.RelativePath, sniffedType, prefetchBuf)
 	}
+	return renderers[ctx.RenderOptions.MarkupType]
+}
 
-	renderer := renderers[ctx.RenderOptions.MarkupType]
+func (ctx *RenderContext) DetectMarkupRendererByReader(in io.Reader) (Renderer, io.Reader, error) {
+	prefetchBuf := make([]byte, 512)
+	n, err := util.ReadAtMost(in, prefetchBuf)
+	if err != nil && err != io.EOF {
+		return nil, nil, err
+	}
+	prefetchBuf = prefetchBuf[:n]
+	renderer := ctx.DetectMarkupRenderer(prefetchBuf)
 	if renderer == nil {
-		return nil, util.NewNotExistErrorf("unsupported markup type: %q", ctx.RenderOptions.MarkupType)
+		return nil, nil, util.NewInvalidArgumentErrorf("unable to find a render")
 	}
-
-	return renderer, nil
+	return renderer, io.MultiReader(bytes.NewReader(prefetchBuf), in), nil
 }
 
 func RendererNeedPostProcess(renderer Renderer) bool {
@@ -170,12 +179,12 @@ func RendererNeedPostProcess(renderer Renderer) bool {
 }
 
 // Render renders markup file to HTML with all specific handling stuff.
-func Render(ctx *RenderContext, input io.Reader, output io.Writer) error {
-	renderer, err := FindRendererByContext(ctx)
+func Render(rctx *RenderContext, origInput io.Reader, output io.Writer) error {
+	renderer, input, err := rctx.DetectMarkupRendererByReader(origInput)
 	if err != nil {
 		return err
 	}
-	return RenderWithRenderer(ctx, renderer, input, output)
+	return RenderWithRenderer(rctx, renderer, input, output)
 }
 
 // RenderString renders Markup string to HTML with all specific handling stuff and return string
@@ -287,12 +296,14 @@ func Init(renderHelpFuncs *RenderHelperFuncs) {
 	}
 
 	// since setting maybe changed extensions, this will reload all renderer extensions mapping
-	extRenderers = make(map[string]Renderer)
+	fileNameRenderers = make(map[string]Renderer)
 	for _, renderer := range renderers {
-		for _, ext := range renderer.Extensions() {
-			extRenderers[strings.ToLower(ext)] = renderer
+		for _, pattern := range renderer.FileNamePatterns() {
+			fileNameRenderers[pattern] = renderer
 		}
 	}
+
+	RefreshFileNamePatterns()
 }
 
 func ComposeSimpleDocumentMetas() map[string]string {