Version-gated language features

verikt uses a feature matrix to generate version-appropriate code. Instead of targeting the lowest common denominator, templates use feature flags to emit modern APIs when the target language version supports them.

How It Works

Detect version — verikt reads the language version from your project (language-specific, see below)
Resolve features — the detected version is compared against features.yaml, producing a boolean map
Inject into templates — templates access features via {{if .Features.<name>}}...{{end}}

Language-specific version detection

How verikt detects the runtime version depends on the language:

Go — runs go env GOVERSION, or accepts an override via --set GoVersion=X.XX
TypeScript — runs node --version, or accepts an override via --set NodeVersion=XX

Go Feature Matrix

Each feature maps to the minimum Go version that introduced it. If your detected version is >= the since version, the feature is enabled.

Feature	Description	Since
`slices_package`	stdlib slices package (`slices.SortFunc`, `slices.Contains`)	1.21
`log_slog`	stdlib structured logging (`log/slog`)	1.21
`maps_package`	stdlib maps package	1.21
`range_over_int`	`for i := range n` syntax	1.22
`range_over_func`	`for x := range func` syntax (iterators)	1.23
`os_root`	`os.Root`/`os.OpenRoot` for kernel-level path safety	1.24
`weak_pointers`	`weak` package for weak pointers	1.24
`os_root_fs`	`os.Root` implements `fs.FS` interface	1.25
`synctest`	`testing/synctest` for concurrent test control	1.25
`generic_type_aliases`	Fully generic type aliases	1.25

Template Usage

Templates use the .Features map to conditionally emit code:

{{if .Features.os_root}}
root, err := os.OpenRoot(dir)
{{else}}
f, err := os.Open(filepath.Join(dir, name))
{{end}}

{{if .Features.log_slog}}
import "log/slog"
{{else}}
import "log"
{{end}}

features.yaml Format

The feature matrix is a YAML file with a single features list:

features:
  - name: slices_package
    description: "stdlib slices package (slices.SortFunc, slices.Contains)"
    since: "1.21"

Field	Type	Description
`name`	string	Identifier used in templates as `.Features.<name>`
`description`	string	Human-readable explanation of the feature
`since`	string	Minimum version that supports this feature

TypeScript / Node.js Feature Matrix

Node.js versions gate TypeScript-specific template behavior. The default Node version is 22 (current Active LTS). Override with --set NodeVersion=24.

Feature	Description	Since
`native_ts`	Stable native TypeScript (`--strip-types` enabled by default) — drops `tsx` dependency, uses `node --watch`	24
`es2024`	ES2024 target support (`Object.groupBy`, `Promise.withResolvers`, `ArrayBuffer.transfer`)	24

What changes by Node version:

Template concern	Node 20	Node 22 (default)	Node 24
`tsconfig.json` target	ES2023	ES2023	ES2024
Dev server	`tsx watch`	`tsx watch`	`node --watch` (native)
`tsx` dependency	Required	Required	Dropped
Dockerfile base	`node:20-alpine`	`node:22-alpine`	`node:24-alpine`
`@types/node`	`^20`	`^22`	`^24`

Adding Features

When a new Go or Node.js version ships with relevant changes:

Add an entry to the provider’s features.yaml
Update any templates that should use the new feature with {{if .Features.<name>}}
Optionally add conditional rules in capability manifests for file-level gating (see verikt.yaml reference)

No changes to the feature resolver are needed — it reads features.yaml dynamically.