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refactor(source-map): narrow internal traversal types #102

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Merged
luojiyin1987 merged 1 commit into from
Aug 15, 2026
Merged

refactor(source-map): narrow internal traversal types #102

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40 changes: 33 additions & 7 deletions src/source-map/build-source-map.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,21 @@ interface RecordingState {
urlSourceSpans: WeakMap<object, SourceSpan>
}

interface TraversableNode {
type: string
position?: ParsedPosition
children?: TraversableNode[]
value?: unknown
url?: unknown
}

function hasStringField<Field extends 'value' | 'url'>(
node: TraversableNode,
field: Field,
): node is TraversableNode & Record<Field, string> {
return field in node && typeof node[field] === 'string';
}

// micromark limits named character references to 31 code units; numeric
// references are shorter. Include the leading `&` and trailing `;` so URL
// mapping only considers parser-valid candidates and never scans an entire
Expand Down Expand Up @@ -556,16 +571,22 @@ export const parseMdWithSourceMap = (md: string): ParsedMarkdownDocument => {
const originalOffsets = new WeakMap<object, readonly [number, number]>();
const sourceGapPrefixes = new WeakMap<MarkdownSourceMapSegment[], number[]>();

function indexNode(node: any): void {
function indexNode(node: TraversableNode): void {
// The standard mdast handler compiles inline code.
// The completed node contains enough data to build its mapping.
if (node.type === 'inlineCode' && typeof node.value === 'string') {
if (
node.type === 'inlineCode'
&& hasStringField(node, 'value')
) {
const segments = buildInlineCodeSegments(md, node);
if (segments)
state.inlineCodeSegments.set(node, segments);
}

if (node.type === 'code' && typeof node.value === 'string') {
if (
node.type === 'code'
&& hasStringField(node, 'value')
) {
const mapping = buildCodeSegments(md, node);
if (mapping) {
state.codeSegments.set(node, mapping.segments);
Expand All @@ -577,7 +598,7 @@ export const parseMdWithSourceMap = (md: string): ParsedMarkdownDocument => {

if (
(node.type === 'link' || node.type === 'definition')
&& typeof node.url === 'string'
&& hasStringField(node, 'url')
) {
const bounds = state.urlSourceSpans.get(node);
const segments = bounds ? buildUrlSegments(md, node, bounds) : undefined;
Expand All @@ -593,12 +614,17 @@ export const parseMdWithSourceMap = (md: string): ParsedMarkdownDocument => {
|| state.inlineCodeSegments.get(node)
|| state.codeSegments.get(node);
if (mappedSegments) {
originalValues.set(node, node.value);
if (hasStringField(node, 'value'))
originalValues.set(node, node.value);
sourceGapPrefixes.set(mappedSegments, buildSourceGapPrefix(mappedSegments));
}
if (state.urlSegments.has(node))
if (
state.urlSegments.has(node)
&& hasStringField(node, 'url')
) {
originalUrls.set(node, node.url);
const position = (node as { position?: ParsedPosition }).position;
}
const position = node.position;
if (position && position.start && position.end) {
originalOffsets.set(node, [position.start.offset, position.end.offset]);
}
Expand Down