Editor preview support for external renderers (#23333)

Remove `[repository.editor] PREVIEWABLE_FILE_MODES` setting that seemed
like it was intended to support this but did not work. Instead, whenever
viewing a file shows a preview, also have a Preview tab in the file
editor.

Add new `/markup` web and API endpoints with `comment`, `gfm`,
`markdown` and new `file` mode that uses a file path to determine the
renderer.

Remove `/markdown` web endpoint but keep the API for backwards and
GitHub compatibility.

## ⚠️ BREAKING ⚠️

The `[repository.editor] PREVIEWABLE_FILE_MODES` setting was removed.
This setting served no practical purpose and was not working correctly.
Instead a preview tab is always shown in the file editor when supported.

---------

Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

8 files changed, 77 insertions, 12 deletions

diff --git a/templates/repo/diff/box.tmpl b/templates/repo/diff/box.tmpl
index 6dafe6f896..8926c518ae 100644
--- a/templates/repo/diff/box.tmpl
+++ b/templates/repo/diff/box.tmpl
@@ -192,7 +192,7 @@
 				<div class="ui comment form">
 					<div class="ui top attached tabular menu">
 						<a class="active write item">{{$.locale.Tr "write"}}</a>
-						<a class="preview item" data-url="{{$.Repository.Link}}/markdown" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
+						<a class="preview item" data-url="{{$.Repository.Link}}/markup" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
 					</div>
 					<div class="ui bottom attached active write tab segment">
 						<textarea class="review-textarea js-quick-submit" tabindex="1" name="content"></textarea>
diff --git a/templates/repo/diff/comment_form.tmpl b/templates/repo/diff/comment_form.tmpl
index 225e40f7f0..deea6baffb 100644
--- a/templates/repo/diff/comment_form.tmpl
+++ b/templates/repo/diff/comment_form.tmpl
@@ -11,7 +11,7 @@
 		<input type="hidden" name="diff_base_cid">
 		<div class="ui top tabular menu" data-write="write" data-preview="preview">
 			<a class="active item" data-tab="write">{{$.root.locale.Tr "write"}}</a>
-			<a class="item" data-tab="preview" data-url="{{$.root.Repository.Link}}/markdown" data-context="{{$.root.RepoLink}}">{{$.root.locale.Tr "preview"}}</a>
+			<a class="item" data-tab="preview" data-url="{{$.root.Repository.Link}}/markup" data-context="{{$.root.RepoLink}}">{{$.root.locale.Tr "preview"}}</a>
 		</div>
 		<div class="field">
 			<div class="ui active tab" data-tab="write">
diff --git a/templates/repo/editor/edit.tmpl b/templates/repo/editor/edit.tmpl
index 19c5cb007a..737027f590 100644
--- a/templates/repo/editor/edit.tmpl
+++ b/templates/repo/editor/edit.tmpl
@@ -31,15 +31,15 @@
 				<div class="ui top attached tabular menu" data-write="write" data-preview="preview" data-diff="diff">
 					<a class="active item" data-tab="write">{{svg "octicon-code"}} {{if .IsNewFile}}{{.locale.Tr "repo.editor.new_file"}}{{else}}{{.locale.Tr "repo.editor.edit_file"}}{{end}}</a>
 					{{if not .IsNewFile}}
-					<a class="item" data-tab="preview" data-url="{{.Repository.Link}}/markdown" data-context="{{.RepoLink}}/src/{{.BranchNameSubURL}}" data-preview-file-modes="{{.PreviewableFileModes}}" data-markdown-mode="gfm">{{svg "octicon-eye"}} {{.locale.Tr "preview"}}</a>
+					<a class="item" data-tab="preview" data-url="{{.Repository.Link}}/markup" data-context="{{.RepoLink}}/src/{{.BranchNameSubURL}}" data-markup-mode="file">{{svg "octicon-eye"}} {{.locale.Tr "preview"}}</a>
 					<a class="item" data-tab="diff" data-url="{{.RepoLink}}/_preview/{{.BranchName | PathEscapeSegments}}/{{.TreePath | PathEscapeSegments}}" data-context="{{.BranchLink}}">{{svg "octicon-diff"}} {{.locale.Tr "repo.editor.preview_changes"}}</a>
 					{{end}}
 				</div>
 				<div class="ui bottom attached active tab segment" data-tab="write">
 					<textarea id="edit_area" name="content" class="gt-hidden" data-id="repo-{{.Repository.Name}}-{{.TreePath}}"
-						data-url="{{.Repository.Link}}/markdown"
+						data-url="{{.Repository.Link}}/markup"
 						data-context="{{.RepoLink}}"
-						data-markdown-file-exts="{{.MarkdownFileExts}}"
+						data-previewable-extensions="{{.PreviewableExtensions}}"
 						data-line-wrap-extensions="{{.LineWrapExtensions}}">
 {{.FileContent}}</textarea>
 					<div class="editor-loading is-loading"></div>
diff --git a/templates/repo/issue/comment_tab.tmpl b/templates/repo/issue/comment_tab.tmpl
index b8e8d2d9aa..47d6ca9587 100644
--- a/templates/repo/issue/comment_tab.tmpl
+++ b/templates/repo/issue/comment_tab.tmpl
@@ -1,10 +1,10 @@
 	<div class="ui top tabular menu" data-write="write" data-preview="preview">
 		<a class="active item" data-tab="write">{{.locale.Tr "write"}}</a>
-		<a class="item" data-tab="preview" data-url="{{.Repository.Link}}/markdown" data-context="{{.RepoLink}}">{{.locale.Tr "preview"}}</a>
+		<a class="item" data-tab="preview" data-url="{{.Repository.Link}}/markup" data-context="{{.RepoLink}}">{{.locale.Tr "preview"}}</a>
 	</div>
 	<div class="field">
 		<div class="ui bottom active tab" data-tab="write">
-		<textarea id="content" class="edit_area js-quick-submit" name="content" tabindex="4" data-id="issue-{{.RepoName}}" data-url="{{.Repository.Link}}/markdown" data-context="{{.Repo.RepoLink}}">
+		<textarea id="content" class="edit_area js-quick-submit" name="content" tabindex="4" data-id="issue-{{.RepoName}}" data-url="{{.Repository.Link}}/markup" data-context="{{.Repo.RepoLink}}">
 			{{- if .BodyQuery}}{{.BodyQuery}}{{else if .IssueTemplate}}{{.IssueTemplate}}{{else if .PullRequestTemplate}}{{.PullRequestTemplate}}{{else}}{{.content}}{{end -}}
 		</textarea>
 		</div>
diff --git a/templates/repo/issue/view_content.tmpl b/templates/repo/issue/view_content.tmpl
index 3e43701b63..8a55d4e30e 100644
--- a/templates/repo/issue/view_content.tmpl
+++ b/templates/repo/issue/view_content.tmpl
@@ -168,7 +168,7 @@
 	<div class="ui comment form">
 		<div class="ui top tabular menu">
 			<a class="active write item">{{$.locale.Tr "write"}}</a>
-			<a class="preview item" data-url="{{$.Repository.Link}}/markdown" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
+			<a class="preview item" data-url="{{$.Repository.Link}}/markup" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
 		</div>
 		<div class="field">
 			<div class="ui bottom active tab write">
diff --git a/templates/repo/release/new.tmpl b/templates/repo/release/new.tmpl
index 8c4df98d19..692a373dc6 100644
--- a/templates/repo/release/new.tmpl
+++ b/templates/repo/release/new.tmpl
@@ -53,7 +53,7 @@
 					<label>{{.locale.Tr "repo.release.content"}}</label>
 					<div class="ui top tabular menu" data-write="write" data-preview="preview">
 						<a class="active write item" data-tab="write">{{$.locale.Tr "write"}}</a>
-						<a class="preview item" data-tab="preview" data-url="{{$.Repository.Link}}/markdown" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
+						<a class="preview item" data-tab="preview" data-url="{{$.Repository.Link}}/markup" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
 					</div>
 					<div class="ui bottom active tab" data-tab="write">
 						<textarea name="content">{{.content}}</textarea>
diff --git a/templates/repo/wiki/new.tmpl b/templates/repo/wiki/new.tmpl
index 9e9de99022..085af4cbc9 100644
--- a/templates/repo/wiki/new.tmpl
+++ b/templates/repo/wiki/new.tmpl
@@ -21,11 +21,11 @@
 			</div>
 			<div class="ui top attached tabular menu previewtabs" data-write="write" data-preview="preview">
 				<a class="active item" data-tab="write">{{.locale.Tr "write"}}</a>
-				<a class="item" data-tab="preview" data-url="{{$.Repository.Link}}/markdown" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
+				<a class="item" data-tab="preview" data-url="{{$.Repository.Link}}/markup" data-context="{{$.RepoLink}}">{{$.locale.Tr "preview"}}</a>
 			</div>
 			<div class="field content" data-loading="{{.locale.Tr "loading"}}">
 				<div class="ui bottom active tab" data-tab="write">
-					<textarea class="js-quick-submit" id="edit_area" name="content" data-id="wiki-{{.title}}" data-url="{{.Repository.Link}}/markdown" data-context="{{.RepoLink}}">{{if .PageIsWikiEdit}}{{.content}}{{else}}{{.locale.Tr "repo.wiki.welcome"}}{{end}}</textarea>
+					<textarea class="js-quick-submit" id="edit_area" name="content" data-id="wiki-{{.title}}" data-url="{{.Repository.Link}}/markup" data-context="{{.RepoLink}}">{{if .PageIsWikiEdit}}{{.content}}{{else}}{{.locale.Tr "repo.wiki.welcome"}}{{end}}</textarea>
 				</div>
 			</div>
 			<div class="field">
diff --git a/templates/swagger/v1_json.tmpl b/templates/swagger/v1_json.tmpl
index ddcdc94b81..0f7e60c598 100644
--- a/templates/swagger/v1_json.tmpl
+++ b/templates/swagger/v1_json.tmpl
@@ -951,6 +951,38 @@
         }
       }
     },
+    "/markup": {
+      "post": {
+        "consumes": [
+          "application/json"
+        ],
+        "produces": [
+          "text/html"
+        ],
+        "tags": [
+          "miscellaneous"
+        ],
+        "summary": "Render a markup document as HTML",
+        "operationId": "renderMarkup",
+        "parameters": [
+          {
+            "name": "body",
+            "in": "body",
+            "schema": {
+              "$ref": "#/definitions/MarkupOption"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/MarkupRender"
+          },
+          "422": {
+            "$ref": "#/responses/validationError"
+          }
+        }
+      }
+    },
     "/nodeinfo": {
       "get": {
         "produces": [
@@ -17991,7 +18023,7 @@
           "type": "string"
         },
         "Mode": {
-          "description": "Mode to render\n\nin: body",
+          "description": "Mode to render (comment, gfm, markdown)\n\nin: body",
           "type": "string"
         },
         "Text": {
@@ -18005,6 +18037,33 @@
       },
       "x-go-package": "code.gitea.io/gitea/modules/structs"
     },
+    "MarkupOption": {
+      "description": "MarkupOption markup options",
+      "type": "object",
+      "properties": {
+        "Context": {
+          "description": "Context to render\n\nin: body",
+          "type": "string"
+        },
+        "FilePath": {
+          "description": "File path for detecting extension in file mode\n\nin: body",
+          "type": "string"
+        },
+        "Mode": {
+          "description": "Mode to render (comment, gfm, markdown, file)\n\nin: body",
+          "type": "string"
+        },
+        "Text": {
+          "description": "Text markup to render\n\nin: body",
+          "type": "string"
+        },
+        "Wiki": {
+          "description": "Is it a wiki page ?\n\nin: body",
+          "type": "boolean"
+        }
+      },
+      "x-go-package": "code.gitea.io/gitea/modules/structs"
+    },
     "MergePullRequestOption": {
       "description": "MergePullRequestForm form for merging Pull Request",
       "type": "object",
@@ -20835,6 +20894,12 @@
         "type": "string"
       }
     },
+    "MarkupRender": {
+      "description": "MarkupRender is a rendered markup document",
+      "schema": {
+        "type": "string"
+      }
+    },
     "Milestone": {
       "description": "Milestone",
       "schema": {