CodeBlockRef

Preformatted code block with optional language label. Display-only, server-owned.

defaults (class-level)

field	type	default	notes
`code`	`str`	`""`	source code text. Rendered verbatim inside a `<pre><code>`. Whitespace preserved.
`language`	`str`	`""`	informational label (e.g. `"python"`, `"rust"`). No syntax highlighting in v1.
`show_copy`	`bool`	`True`	render a copy-to-clipboard button. Browser-only affordance; no server notify.

Declared as plain class attributes on the python CodeBlockRef. Empty defaults are omitted from the mount payload: only keys that differ from "" / True ride in on props. The browser slice seeds from the props dict, falling back to the same defaults if absent.

interactions

op	dir	payload	nu method	notes
`write`	server -> tab	`{code?: str, language?: str}`	`store`	partial dict; missing keys leave slice fields alone.
`write`	server -> tab	`{code: str}`	`store_code`	full replace of the code text. nil decodes to `""`.
`write`	server -> tab	`{language: str}`	`store_language`	replaces the language label. nil decodes to `""`.

One wire op (write) with a dict payload. The nu-side methods just shape the dict. No append, no read, no notify. The copy button does not emit a frame.

show_copy is reachable via the generic write op (any key in the dict is merged) but has no dedicated nu method in v1; treat it as a class default in practice.

wire payloads

// mount field entry (only when at least one default differs from the seed)
{"path": "HomePage.snippet", "type": "CodeBlockRef", "props": {"code": "print(1)\n", "language": "python"}}

// server pushes a full snippet
{"op": "write", "ref": "HomePage.snippet", "payload": {"code": "fn main() {}\n", "language": "rust"}}

// server changes only the language label
{"op": "write", "ref": "HomePage.snippet", "payload": {"language": "rust"}}

// server clears the code via Nu sentinel
{"op": "write", "ref": "HomePage.snippet", "payload": {"code": null}}

// server toggles the copy button off
{"op": "write", "ref": "HomePage.snippet", "payload": {"show_copy": false}}

renderer

web/src/refs/code-block.tsx. A <div> wraps a small header (language label on the left, copy button on the right, both conditional) and a <pre><code> body. shadcn / radix not required; a plain <button> with onClick={() => navigator.clipboard.writeText(code)} handles the copy. Tailwind classes: font-mono text-sm bg-muted rounded p-3 overflow-x-auto. No external highlighter.

slice shape

{
  type: "CodeBlockRef",
  code: string,
  language: string,
  show_copy: boolean,
  write: (payload: {code?: string|null, language?: string|null, show_copy?: boolean|null}) => void,
}

Seeded from props.code / props.language / props.show_copy when present, else the class defaults ("", "", true). write merges any subset of keys; nil on code / language coerces to ""; nil on show_copy coerces to the class default (true).

edge cases

payload missing keys: only declared keys mutate the slice; others stay put.
code or language is msgpack nil: slice field becomes "".
show_copy is msgpack nil: slice field falls back to the class default (true).
slot never written and no props: selector returns the defaults ("", "", true). With empty code and empty language, the renderer still emits an empty <pre> and a copy button that copies an empty string.
header is fully hidden when both language === "" and show_copy === false.
very long single lines: the body uses overflow-x-auto; no soft-wrap.
copy on browsers without navigator.clipboard (insecure context): the call rejects silently; no server notify, no error frame.

non-goals

no syntax highlighting in v1. The language field is a label only. Adding a highlighter (shiki, prismjs, highlight.js) is deferred since it grows the bundle and pulls in a per-language theme story. Revisit once the gallery stabilizes.
no line numbers, no copy-success toast, no notify back to the server on copy.
no diff / unified-patch rendering.
no inline-code variant (use a markdown ref or plain text for that).
no append-stream of partial code chunks; one write per replace.
no caps flags on mount; deferred catalog-wide.