Replace Monaco with CodeMirror (#36764)

- Replace monaco-editor with CodeMirror 6
- Add `--color-syntax-*` CSS variables for all syntax token types,
shared by CodeMirror, Chroma and EasyMDE
- Consolidate chroma CSS into a single theme-independent file
(`modules/chroma.css`)
- Syntax colors in the code editor now match the code view and
light/dark themes
- Code editor is now 12px instead of 14px font size to match code view
and GitHub
- Use a global style for kbd elements
- When editing existing files, focus will be on codemirror instead of
filename input.
- Keyboard shortcuts are roughtly the same as VSCode
- Add a "Find" button, useful for mobile
- Add context menu similar to Monaco
- Add a command palette (Ctrl/Cmd+Shift+P or F1) or via button
- Add clickable URLs via Ctrl/Cmd+click
- Add e2e test for the code editor
- Remove `window.codeEditors` global
- The main missing Monaco features are hover types and semantic rename
but these were not fully working because monaco operated only on single
files and only for JS/TS/HTML/CSS/JSON.

| | Monaco (main) | CodeMirror (cm) | Delta |
|---|---|---|---|
| **Build time** | 7.8s | 5.3s | **-32%** |
| **JS output** | 25 MB | 14 MB | **-44%** |
| **CSS output** | 1.2 MB | 1012 KB | **-17%** |
| **Total (no maps)** | 23.3 MB | 12.1 MB | **-48%** |

Fixes: #36311
Fixes: #14776
Fixes: #12171

<img width="1333" height="555" alt="image"
src="https://github.com/user-attachments/assets/f0fe3a28-1ed9-4f22-bf25-2b161501d7ce"
/>

---------

Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

routers/web/repo/editor.go

@@ -319,7 +319,12 @@ func EditFile(ctx *context.Context) {
 		}
 	}
 
-	ctx.Data["CodeEditorConfig"] = getCodeEditorConfig(ctx, ctx.Repo.TreePath)
+	editorConfig := getCodeEditorConfigByEditorconfig(ctx, ctx.Repo.TreePath)
+	editorConfig.Autofocus = !isNewFile
+	if isNewFile {
+		editorConfig.Filename = ""
+	}
+	ctx.Data["CodeEditorConfig"] = editorConfig
 	ctx.HTML(http.StatusOK, tplEditFile)
 }
 

routers/web/repo/editor_apply_patch.go

@@ -20,7 +20,7 @@ func NewDiffPatch(ctx *context.Context) {
 	}
 
 	ctx.Data["PageIsPatch"] = true
-	ctx.Data["CodeEditorConfig"] = CodeEditorConfig{} // not really editing a file, so no need to fill in the config
+	ctx.Data["CodeEditorConfig"] = CodeEditorConfig{Filename: "diff.patch"}
 	ctx.HTML(http.StatusOK, tplPatchFile)
 }
 

routers/web/repo/editor_util.go

@@ -65,27 +65,33 @@ func getClosestParentWithFiles(gitRepo *git.Repository, branchName, originTreePa
 	return f(originTreePath, commit)
 }
 
-// CodeEditorConfig is also used by frontend, defined in "codeeditor.ts"
+// CodeEditorConfig is also used by frontend, defined in "codeeditor" module
 type CodeEditorConfig struct {
-	PreviewableExtensions []string `json:"previewable_extensions"`
-	LineWrapExtensions    []string `json:"line_wrap_extensions"`
-	LineWrapOn            bool     `json:"line_wrap_on"`
+	Filename              string   `json:"filename"` // the base name, not full path
+	Autofocus             bool     `json:"autofocus"`
+	PreviewableExtensions []string `json:"previewableExtensions,omitempty"`
+	LineWrapExtensions    []string `json:"lineWrapExtensions,omitempty"`
+	LineWrap              bool     `json:"lineWrap"`
+	Previewable           bool     `json:"previewable,omitempty"`
 
-	IndentStyle            string `json:"indent_style"`
-	IndentSize             int    `json:"indent_size"`
-	TabWidth               int    `json:"tab_width"`
-	TrimTrailingWhitespace *bool  `json:"trim_trailing_whitespace,omitempty"`
+	// the following can be read from .editorconfig if exists, or use default value
+	IndentStyle            string `json:"indentStyle"` // in most cases, keep it empty by default, detected by the source code
+	IndentSize             int    `json:"indentSize"`
+	TabWidth               int    `json:"tabWidth"`
+	TrimTrailingWhitespace *bool  `json:"trimTrailingWhitespace,omitempty"`
 }
 
-func getCodeEditorConfig(ctx *context_service.Context, treePath string) (ret CodeEditorConfig) {
+func getCodeEditorConfigByEditorconfig(ctx *context_service.Context, treePath string) CodeEditorConfig {
+	ret := CodeEditorConfig{Filename: path.Base(treePath)}
 	ret.PreviewableExtensions = markup.PreviewableExtensions()
 	ret.LineWrapExtensions = setting.Repository.Editor.LineWrapExtensions
-	ret.LineWrapOn = util.SliceContainsString(ret.LineWrapExtensions, path.Ext(treePath), true)
+	ret.LineWrap = util.SliceContainsString(ret.LineWrapExtensions, path.Ext(treePath), true)
+	ret.Previewable = util.SliceContainsString(ret.PreviewableExtensions, path.Ext(treePath), true)
 	ec, _, err := ctx.Repo.GetEditorconfig()
 	if err == nil {
 		def, err := ec.GetDefinitionForFilename(treePath)
 		if err == nil {
-			ret.IndentStyle = def.IndentStyle
+			ret.IndentStyle = util.IfZero(def.IndentStyle, ret.IndentStyle)
 			ret.IndentSize, _ = strconv.Atoi(def.IndentSize)
 			ret.TabWidth = def.TabWidth
 			ret.TrimTrailingWhitespace = def.TrimTrailingWhitespace

routers/web/repo/setting/git_hooks.go

@@ -42,7 +42,7 @@ func GitHooksEdit(ctx *context.Context) {
 		return
 	}
 	ctx.Data["Hook"] = hook
-	ctx.Data["CodeEditorConfig"] = repo.CodeEditorConfig{} // not really editing a repo file, so no editor config
+	ctx.Data["CodeEditorConfig"] = repo.CodeEditorConfig{Filename: name + ".sh", IndentStyle: "tab", TabWidth: 4}
 	ctx.HTML(http.StatusOK, tplGithookEdit)
 }