, so the code surface's mono face, pre whitespace and token color would cascade into real buttons placed here. Reset to app typography at the boundary. */ "text-foreground z-20 items-center gap-1 font-sans whitespace-normal select-none", !inGutter && "absolute end-2 top-0 flex h-(--code-block-line-height)", /* ABSOLUTE and centred on the row's START EDGE: `left-0` is where the code column begins (the row box already excludes the gutter), and the -50% translate hangs the control half over the number column, half over the code - the editor treatment. Being out of flow on BOTH axes is the point: an in-flow version pushed the code right by its own width, and an earlier block level one broke the row onto a new line. The control travels with the code on a horizontal scroll; it cannot also be sticky. */ inGutter && "absolute top-1/2 left-0 flex -translate-x-1/2 -translate-y-1/2 items-center justify-center" )} > {actions({ line: line.number, text: line.text, state })} ) : null} {/* An empty line needs an explicit break. Copying a selection relies on the browser emitting a newline between block-level rows, and a row with no text at all contributes neither text nor separator, so a blank line silently vanishes from the pasted source. */} {line.tokens.length === 0 ?
: null} {folded && hiddenCount > 0 ? ( /* `select-none` is doing real work: a manual drag-select over a folded block would otherwise paste this chip into the middle of the source. The copy button reads the raw code and never sees it. */ ) : null} {caret ? ( ) }) /* -------------------------------------------------------------------------- */ /* Root */ /* -------------------------------------------------------------------------- */ export type CodeBlockProps = { code?: string language?: string lines?: CodeBlockLine[] themes?: CodeBlockThemes highlight?: boolean showLineNumbers?: boolean startLine?: number wrap?: boolean defaultWrap?: boolean onWrapChange?: (wrap: boolean) => void maxLines?: number variant?: "default" | "ghost" label?: string highlightedLines?: CodeBlockLineSpec highlightedWords?: CodeBlockWordSpec[] focusedLines?: CodeBlockLineSpec diff?: CodeBlockDiffSpec lineLevels?: CodeBlockLevelSpec transformers?: CodeBlockTransformer[] streaming?: boolean selectable?: boolean selectedLines?: number[] defaultSelectedLines?: number[] onSelectedLinesChange?: (lines: number[]) => void /** Screen-reader text announced when a stream finishes, for localisation. */ completeAnnouncement?: string /** Collapsed state under `maxLines`, controlled. */ expanded?: boolean defaultExpanded?: boolean onExpandedChange?: (expanded: boolean) => void /** Detects fold regions from indentation and renders a toggle per region. */ foldable?: boolean /** * Replaces the indentation heuristic with your own regions (source-numbered, * like every line spec) - grammar folding, JSON blocks, patch hunks. * Implies nothing about `foldable`; pass both. */ foldRegions?: CodeBlockFoldRegion[] /** Folded regions by start line, 1-based within `code`. Controlled. */ folded?: number[] /** Folded regions by their start line, uncontrolled. */ defaultFolded?: number[] onFoldedChange?: (folded: number[]) => void children?: ReactNode } & Omit, "children" | "onSelect"> /** * The root. `` is a complete block; * passing `lines` from a server component skips the client highlighter and * shiki entirely. Children are CHROME ONLY: the root renders the code surface * itself, so child order never matters and a wrapper cannot break scrolling. */ function CodeBlock({ code, language, lines: linesProp, themes, highlight = true, showLineNumbers = false, startLine = 1, wrap: wrapProp, defaultWrap = false, onWrapChange, maxLines, variant = "default", label, highlightedLines, highlightedWords, focusedLines, diff, lineLevels, transformers, streaming = false, selectable = false, selectedLines, defaultSelectedLines, onSelectedLinesChange, completeAnnouncement, expanded: expandedProp, defaultExpanded = false, onExpandedChange, foldable = false, foldRegions: foldRegionsProp, folded, defaultFolded, onFoldedChange, className, children, ...props }: CodeBlockProps) { const contentId = useId() const source = code ?? "" const resolvedLanguage = resolveCodeBlockLanguage(language) /* The deferred copy is what a fast stream tokenises against. React keeps the previous render on screen while the new one is prepared, so the block never blanks and the main thread is never blocked by a chunk. */ const deferredSource = useDeferredValue(source) const plainLines = useMemo( () => toPlainLines(deferredSource, startLine), [deferredSource, startLine] ) /* The result is tagged with the exact inputs that produced it. Without the tag, swapping `code` kept rendering the PREVIOUS document for the whole async highlight pass - or spliced two files together when the old result was shorter than the new source. */ const [highlighted, setHighlighted] = useState<{ source: string spec: string lines: CodeBlockLine[] } | null>(null) const shouldHighlight = !linesProp && highlight && Boolean(resolvedLanguage) && source.length > 0 /* Presentation props enter the effect as ONE serialized key: they are inline literals at most call sites, and reference deps would re-tokenize per parent render. The effect parses its inputs back out of the key, so used and depended-on values cannot drift. `transformers` holds functions and stays a reference dep - hoist it to module scope. */ const specKey = JSON.stringify([ themes ?? null, startLine, highlightedLines ?? null, highlightedWords ?? null, focusedLines ?? null, diff ?? null, lineLevels ?? null, ]) const transformersWarnedRef = useRef(false) const previousTransformersRef = useRef(transformers) useEffect(() => { if ( process.env.NODE_ENV !== "production" && streaming && previousTransformersRef.current !== transformers && !transformersWarnedRef.current ) { transformersWarnedRef.current = true console.warn( "[code-block] `transformers` changed identity during a stream, which " + "re-tokenizes the whole document per chunk. Hoist the array to " + "module scope or memoize it." ) } previousTransformersRef.current = transformers }, [transformers, streaming]) useEffect(() => { if (!shouldHighlight) { setHighlighted(null) return } const [ specThemes, specStartLine, specHighlightedLines, specHighlightedWords, specFocusedLines, specDiff, specLineLevels, ] = JSON.parse(specKey) as [ CodeBlockThemes | null, number, CodeBlockLineSpec | null, CodeBlockWordSpec[] | null, CodeBlockLineSpec | null, CodeBlockDiffSpec | null, CodeBlockLevelSpec | null, ] let active = true void highlightCode(deferredSource, { language, instanceKey: contentId, themes: specThemes ?? undefined, transformers, startLine: specStartLine, highlightedLines: specHighlightedLines ?? undefined, highlightedWords: specHighlightedWords ?? undefined, focusedLines: specFocusedLines ?? undefined, diff: specDiff ?? undefined, lineLevels: specLineLevels ?? undefined, }).then((next) => { if (active) { setHighlighted({ source: deferredSource, spec: specKey, lines: next }) } }) return () => { active = false } }, [shouldHighlight, deferredSource, language, transformers, specKey]) /* Plain text is the floor, never a blank frame: the highlighter runs a chunk behind a stream, so its lines show as-is and the remainder appends as plain text that gains colour a frame later. */ const lines = useMemo(() => { if (linesProp) return linesProp if (!shouldHighlight || !highlighted) return plainLines /* The merge below is only valid under the STREAMING invariant: the highlighted source must be a prefix of what is on screen, with the same presentation spec. A swapped `code` or spec falls back to plain text for one highlight pass instead of showing the previous document. */ if ( highlighted.spec !== specKey || !deferredSource.startsWith(highlighted.source) ) { return plainLines } if (highlighted.lines.length >= plainLines.length) return highlighted.lines return [...highlighted.lines, ...plainLines.slice(highlighted.lines.length)] }, [ linesProp, shouldHighlight, highlighted, plainLines, deferredSource, specKey, ]) const focusMode = useMemo( () => lines.some((line) => line.state?.focused), [lines] ) const hasDiff = useMemo(() => lines.some((line) => line.state?.diff), [lines]) const [internalWrap, setInternalWrap] = useState(defaultWrap) const wrap = wrapProp ?? internalWrap const setWrap = useCallback( (next: boolean) => { if (wrapProp === undefined) setInternalWrap(next) onWrapChange?.(next) }, [wrapProp, onWrapChange] ) const collapsible = typeof maxLines === "number" && lines.length > maxLines const [internalExpanded, setInternalExpanded] = useState(defaultExpanded) const expanded = expandedProp ?? internalExpanded const setExpanded = useCallback( (next: boolean) => { if (expandedProp === undefined) setInternalExpanded(next) onExpandedChange?.(next) }, [expandedProp, onExpandedChange] ) const isExpanded = collapsible ? expanded : true const [internalSelected, setInternalSelected] = useState( defaultSelectedLines ?? [] ) const selection = selectedLines ?? internalSelected const selectedSet = useMemo(() => new Set(selection), [selection]) const lastSelectedRef = useRef(null) /* Latest-value refs, so the toggle callbacks below can be created ONCE. With state in their dep lists every selection or fold change minted new identities, which reached every row through `onSelect`/`onToggleFold` and busted the row memo the streaming design rests on. */ const selectionStateRef = useRef({ selection, selectedSet, controlled: selectedLines !== undefined, onSelectedLinesChange, }) selectionStateRef.current = { selection, selectedSet, controlled: selectedLines !== undefined, onSelectedLinesChange, } const commitSelection = useCallback((next: number[]) => { if (!selectionStateRef.current.controlled) setInternalSelected(next) selectionStateRef.current.onSelectedLinesChange?.(next) }, []) const toggleLine = useCallback( (line: number, extend: boolean) => { const anchor = lastSelectedRef.current const { selection, selectedSet } = selectionStateRef.current if (extend && anchor !== null) { const from = Math.min(anchor, line) const to = Math.max(anchor, line) const range: number[] = [] for (let value = from; value <= to; value += 1) range.push(value) commitSelection(range) return } lastSelectedRef.current = line commitSelection( selectedSet.has(line) ? selection.filter((value) => value !== line) : [...selection, line].sort((a, b) => a - b) ) }, [commitSelection] ) /* Regions are SOURCE-numbered (1-based within `code`), like every other line spec, so `folded` values and `highlightedLines` values interchange. */ const foldRegions = useMemo(() => { if (!foldable) return EMPTY_FOLD_REGIONS if (foldRegionsProp) return foldRegionsProp return computeFoldRegions(lines).map((region) => ({ start: region.start - startLine + 1, end: region.end - startLine + 1, })) }, [foldable, foldRegionsProp, lines, startLine]) const foldStarts = useMemo( () => new Map(foldRegions.map((region) => [region.start, region])), [foldRegions] ) const [internalFolded, setInternalFolded] = useState( defaultFolded ?? [] ) const foldedValue = folded ?? internalFolded const foldedSet = useMemo(() => new Set(foldedValue), [foldedValue]) /* Same latest-value shape as selection, for the same row-memo reason. */ const foldStateRef = useRef({ foldedValue, foldedSet, controlled: folded !== undefined, onFoldedChange, }) foldStateRef.current = { foldedValue, foldedSet, controlled: folded !== undefined, onFoldedChange, } const commitFolded = useCallback((next: number[]) => { if (!foldStateRef.current.controlled) setInternalFolded(next) foldStateRef.current.onFoldedChange?.(next) }, []) const toggleFold = useCallback( (start: number) => { const { foldedValue, foldedSet } = foldStateRef.current commitFolded( foldedSet.has(start) ? foldedValue.filter((value) => value !== start) : [...foldedValue, start].sort((a, b) => a - b) ) }, [commitFolded] ) /** * A line is hidden when ANY folded region covers it, and that one rule is * what makes nesting work without a tree: folding an outer region swallows * the inner toggles as well, their own folded state survives untouched * underneath, and unfolding the outer one restores exactly what the reader * left behind rather than a flattened block. */ const renderedLines = useMemo(() => { if (!foldable || foldedSet.size === 0) return lines const hidden = new Set() for (const start of foldedSet) { const region = foldStarts.get(start) if (!region) continue for (let n = region.start + 1; n <= region.end; n += 1) { hidden.add(n + startLine - 1) } } return lines.filter((line) => !hidden.has(line.number)) }, [foldable, foldedSet, foldStarts, lines, startLine]) const configValue = useMemo( () => ({ language, resolvedLanguage, showLineNumbers, wrap, setWrap, wrapControlled: wrapProp !== undefined, expanded: isExpanded, setExpanded, collapsible, streaming, contentId, }), [ language, resolvedLanguage, showLineNumbers, wrap, setWrap, wrapProp, isExpanded, collapsible, streaming, contentId, ] ) const clearSelection = useCallback( () => commitSelection([]), [commitSelection] ) const documentValue = useMemo( () => ({ code: source, lines, selected: selectedSet, selectable, toggleLine, clearSelection, foldable, foldRegions, folded: foldedSet, toggleFold, setFolded: commitFolded, }), [ source, lines, selectedSet, selectable, toggleLine, clearSelection, foldable, foldRegions, foldedSet, toggleFold, commitFolded, ] ) const visibleLines = collapsible && !isExpanded ? maxLines : undefined /* Detected from the element type rather than a `:has()` selector. This repo has measured `:has()` at 85-120ms of style invalidation per DOM mutation, and a streaming block mutates on every chunk, so the primitive uses none. */ const hasHeader = containsElementType(children, CodeBlockHeader) const [lineActions, setLineActions] = useState(null) const [actionsSide, setActionsSide] = useState("end") const actionsOwnerRef = useRef