Gen devcontainer

Skill thettwe/nyann/skills/gen-devcontainer

Nyann (ငြမ်း) is Burmese for scaffolding. Nyann is a Claude Code plugin that sets up and maintains project governance.

Install

npx -y skills add thettwe/nyann --skill gen-devcontainer

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

One thing to look at

6 stars6 stars. Stars are a popularity signal and not a quality one, but at this level it is likely that nobody has read this closely except its author, and you would be relying on your own review.

What its author says it does

Copied from the file, not written here

Generate a `.devcontainer/devcontainer.json` keyed to the project's primary language so `gh codespace create` (or VS Code's "Reopen in Container") gives anyone on the team a ready-to-go env with the right runtime, GH CLI, git-lfs, and language-tier VS Code extensions pre-installed. Preview-by-default; idempotent on apply (no-op on identical bytes, diff-and-refuse on divergence unless `--force-overwrite`). TRIGGER when the user says "add a devcontainer", "set up codespaces", "scaffold devcontainer.json", "reopen in container", "configure dev environment", "containerized dev env", "make this work in codespaces", "add VS Code container", "wire up devcontainer", "/nyann:gen-devcontainer". Also trigger when a user asks "how do I run this in Codespaces" and there's no `.devcontainer/` directory yet. Do NOT trigger on "build a Docker image for production" — that's a Dockerfile concern outside devcontainer scope. Do NOT trigger on "fix my devcontainer build" — that's debugging an existing setup, not generating one (read the file with the user instead).

SKILL.md

7.2 KB, as published. Nobody here has run it

gen-devcontainer

Wraps bin/gen-devcontainer.sh. Emits a devcontainer.json; preview- by-default; idempotent on apply.

When to trigger

User wants a Codespaces-ready repo and there's no .devcontainer/ directory yet.
User wants to refresh an existing devcontainer.json after upgrading nyann (base image tags + extension lists shift with the snapshot_version comment in the file).
User wants to add forwarded ports / cpus / memory to an existing devcontainer (use --port 3000 --cpus 4 --memory 8gb).

When NOT to trigger

User wants a production Dockerfile — that's an entirely different concern; devcontainer.json is dev-environment only.
User wants to debug a broken devcontainer build — open the existing file with them; this skill generates fresh, not diagnoses.
User is on a non-Codespaces, non-VS Code editor — the file still works under JetBrains' Dev Containers plugin and devcontainer open (CLI), but flag the broader VS Code-first defaults.

Picking the language

Read StackDescriptor.primary_language from bin/detect-stack.sh:

StackDescriptor.primary_language	--language
`typescript` / `javascript`	`node`
`python`	`python`
`go`	`go`
`rust`	`rust`
`dart`	`dart`
`java` / `kotlin`	`java`
`csharp` / `dotnet`	`dotnet`
`php`	`php`
`ruby`	`ruby`
`swift`	`swift`
`elixir`	`elixir`
`cpp` / `c`	`cpp`

For polyglot monorepos (workspaces[] present), pick the language of the most-important workspace OR ask the user — running multiple devcontainers from a single repo is uncommon and confusing.

Preview, then apply

Always preview first. Show the rendered JSON; wait for confirmation:

bin/gen-devcontainer.sh --language python --name my-app

Then on confirmation:

bin/gen-devcontainer.sh --language python --name my-app \
  --target . --apply

If the destination already matches: log "unchanged" and exit. If it differs: print the unified diff to stderr, exit 3, prompt the user before re-running with --force-overwrite.

Output shape

.devcontainer/devcontainer.json containing:

$schema pointing at the official devcontainer spec
$comment tagging the nyann snapshot version
name (display name in 'Open in Container' picker)
image (per-language, pinned to a major:minor tag)
features (gh CLI, git-lfs, common-utils — version-pinned)
customizations.vscode.extensions (per-language pack + gitlens + git-graph)
postCreateCommand (per-language dep install — npm ci, uv sync, cargo fetch, etc.)
forwardPorts (when --port flag(s) supplied)
hostRequirements (when --cpus / --memory / --storage supplied)

Defaults explained

Base image: Microsoft devcontainers/<lang> images where they exist (well-maintained, security-scanned, multi-arch). Vendor images for Dart / Swift / Elixir where no MS variant exists.
Image tag: pinned to major:minor, NOT a digest. Operators who need byte-reproducible builds should pin to a digest by hand; the Docker ecosystem of gen-dependency-updater can roll the tag.
Extensions: per-language language pack + gitlens + git-graph baseline. Conservative pick; extend via --extension.
Features: github-cli:1 + git-lfs:1 + common-utils:2, always with a version pin so floating tags can't quietly re-broadcast.
postCreateCommand: best-effort install that no-ops when the expected manifest is missing (so the file works in a partially- scaffolded repo). Override with --post-create-command for non- standard package managers (e.g. pnpm rather than npm).

Reading the output back

When previewing:

Surface the base image (the operator may want to swap to an org-internal mirror).
Surface the postCreateCommand (so they can spot install commands that don't fit their workflow).
Suggest --port flags if the user mentioned a dev-server port in the conversation.

When applying:

Confirm the dest path didn't already exist (or that the diff was intentional if --force-overwrite was used).
Suggest a follow-up gh codespace create invocation if the user asked for Codespaces specifically.