Feature markers

Files owned wholly by one feature are listed in the manifest and dropped whole. Code shared between features (a module that imports five optional services, an .env.example, a Dockerfile) instead carries markers that stack new evaluates line by line.

Syntax

Markers work inside any comment syntax, because they’re found anywhere on a line:

import { CacheService } from './services'; // @feature cache

// @feature:start mail
MailService,
MailProcessor,
// @feature:end

# @feature:start temporal
FROM node:24-bookworm-slim AS build
# @feature:else
FROM aurostack.dev/wesnetech/nodejs:24 AS build
# @feature:end

Marker	Keeps
<code> // @feature x	That one line, if x is on. The marker comment is removed from the kept line
@feature:start x … @feature:end	The block, if x is on
@feature:else	Flips the current block: what follows is kept if x is off

Expressions:

Expression	True when
x	x is on
!x	x is off
a, b	a or b is on

There is no AND. To require two features, nest blocks: an inner block is kept only if every enclosing block is kept.

# @feature:start browser
# @feature:start temporal
RUN apt-get install -y chromium
# @feature:else
RUN apk add chromium
# @feature:end
# @feature:end

<!-- @feature:start x --> and /* @feature x */ work too: a trailing --> or */ is ignored.

Rules that keep templates compiling

Never put an inline marker on the closing line of a multi-line construct

Removing }); // @feature x leaves the opening half behind. Wrap the whole construct in @feature:start / @feature:end instead. stack doctor checks bracket balance in .ts files for every feature selection and reports this.

• Avoid :else in TypeScript. Both branches are present in the template itself, and two definitions of the same thing won’t compile. Use it in Dockerfiles, YAML, .env and Markdown.
• Keep list elements removable. A list that would become empty when every optional entry is removed needs one permanent element.
• Don’t hand-format around markers. Generation runs the formatter afterwards; blank-line runs left by removed blocks collapse to one.
• Strict JSON can’t carry markers. package.json dependencies are removed through the manifest’s packageJson instead. JSONC files like tsconfig.json can use comment markers.
• A misspelt feature name deletes code. stack doctor fails on any marker naming an undeclared feature.