Colorful tmpl — rainbow highlighting for Go templates

Rainbow nesting backgrounds, variable spotting, and {{ }} injection into any host language.

Colorful Go template syntax highlighting

What it does

Rainbow backgrounds — each nesting level (if / range / with / define) gets a distinct background color, rotating through 6 levels.
Variable spotting — $x := definitions glow green, $x = assignments glow orange, $x uses glow blue.
TextMate grammar — foreground scope coloring in diff/peek views.
Semantic tokens — variable definitions vs. uses are classified so themes can style them.
Injection grammar — {{ }} actions are highlighted and rainbow-decorated inside any host language without losing that language's own syntax coloring.

How it works

flowchart LR
  src["Go template source"] --> lexer["@colorful-tmpl/highlight-core lexer"]
  lexer -->|"nesting levels"| deco["rainbow decorator (VS Code)"]
  grammar["gotmpl.tmLanguage.json"] --> deco
  sem["semantic token provider"] --> deco
  deco --> editor["editor"]

Choosing a language mode

File type	Language mode to set	Why
Pure Go template (`.gotmpl`, `.gohtml`, …)	Colorful Go Template	The file IS the template; no base syntax to preserve.
Template wrapping CMake, SQL, YAML, …	Keep the base language (`cmake`, `sql`, `yaml`, …)	The injection grammar adds `{{ }}` scopes on top; the decorator runs automatically.

For mixed templates, add patterns to files.associations — more specific globs win:

// .vscode/settings.json or user settings
"files.associations": {
  // pure templates → colorful-tmpl
  "*.gotmpl": "colorful-tmpl",
  "*.gohtml": "colorful-tmpl",
  // mixed templates → base language (more specific patterns take priority)
  "CMakeLists.*.tmpl": "cmake",
  "*.cmake.tmpl": "cmake",
  "*.yaml.tmpl": "yaml",
  "*.sql.tmpl": "sql",
  "*.sh.tmpl": "shellscript",
  "*.py.tmpl": "python",
  "*.java.tmpl": "java",
  // fallback for any remaining .tmpl
  "*.tmpl": "colorful-tmpl"
}

Settings

Key	Default	Description
`colorful-tmpl.rainbow.enabled`	`true`	Enable/disable all rainbow backgrounds.
`colorful-tmpl.rainbow.palette`	6 rgba colors	Background colors per nesting level (rotates).
`colorful-tmpl.rainbow.variableHighlight`	`true`	Enable/disable the variable spotting highlights.
`colorful-tmpl.rainbow.variableDefColor`	theme green	Background color for `$x :=` definitions.
`colorful-tmpl.rainbow.variableAssignColor`	theme orange	Background color for `$x =` assignments.
`colorful-tmpl.rainbow.variableUseColor`	theme blue	Background color for `$x` uses.

Installation

Install from the VS Code Marketplace: ext install d-led.colorful-tmpl.

License

MPL-2.0

Colorful tmpl

Dmitry L.