129 lines
4 KiB
TypeScript
129 lines
4 KiB
TypeScript
import type { Expression, Super } from 'estree';
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import Slugger from 'github-slugger';
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import type { MdxTextExpression } from 'mdast-util-mdx-expression';
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import type { Node } from 'unist';
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import { visit } from 'unist-util-visit';
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import { InvalidAstroDataError, safelyGetAstroData } from './frontmatter-injection.js';
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import type { MarkdownAstroData, MarkdownHeading, MarkdownVFile, RehypePlugin } from './types.js';
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const rawNodeTypes = new Set(['text', 'raw', 'mdxTextExpression']);
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const codeTagNames = new Set(['code', 'pre']);
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export function rehypeHeadingIds(): ReturnType<RehypePlugin> {
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return function (tree, file: MarkdownVFile) {
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const headings: MarkdownHeading[] = [];
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const slugger = new Slugger();
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const isMDX = isMDXFile(file);
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const astroData = safelyGetAstroData(file.data);
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visit(tree, (node) => {
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if (node.type !== 'element') return;
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const { tagName } = node;
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if (tagName[0] !== 'h') return;
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const [, level] = tagName.match(/h([0-6])/) ?? [];
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if (!level) return;
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const depth = Number.parseInt(level);
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let text = '';
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visit(node, (child, __, parent) => {
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if (child.type === 'element' || parent == null) {
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return;
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}
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if (child.type === 'raw') {
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if (child.value.match(/^\n?<.*>\n?$/)) {
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return;
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}
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}
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if (rawNodeTypes.has(child.type)) {
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if (isMDX || codeTagNames.has(parent.tagName)) {
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let value = child.value;
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if (isMdxTextExpression(child) && !(astroData instanceof InvalidAstroDataError)) {
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const frontmatterPath = getMdxFrontmatterVariablePath(child);
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if (Array.isArray(frontmatterPath) && frontmatterPath.length > 0) {
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const frontmatterValue = getMdxFrontmatterVariableValue(astroData, frontmatterPath);
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if (typeof frontmatterValue === 'string') {
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value = frontmatterValue;
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}
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}
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}
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text += value;
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} else {
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text += child.value.replace(/\{/g, '${');
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}
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}
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});
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node.properties = node.properties || {};
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if (typeof node.properties.id !== 'string') {
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let slug = slugger.slug(text);
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if (slug.endsWith('-')) slug = slug.slice(0, -1);
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node.properties.id = slug;
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}
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headings.push({ depth, slug: node.properties.id, text });
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});
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file.data.__astroHeadings = headings;
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};
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}
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function isMDXFile(file: MarkdownVFile) {
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return Boolean(file.history[0]?.endsWith('.mdx'));
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}
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/**
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* Check if an ESTree entry is `frontmatter.*.VARIABLE`.
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* If it is, return the variable path (i.e. `["*", ..., "VARIABLE"]`) minus the `frontmatter` prefix.
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*/
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function getMdxFrontmatterVariablePath(node: MdxTextExpression): string[] | Error {
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if (!node.data?.estree || node.data.estree.body.length !== 1) return new Error();
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const statement = node.data.estree.body[0];
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// Check for "[ANYTHING].[ANYTHING]".
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if (statement?.type !== 'ExpressionStatement' || statement.expression.type !== 'MemberExpression')
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return new Error();
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let expression: Expression | Super = statement.expression;
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const expressionPath: string[] = [];
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// Traverse the expression, collecting the variable path.
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while (
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expression.type === 'MemberExpression' &&
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expression.property.type === (expression.computed ? 'Literal' : 'Identifier')
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) {
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expressionPath.push(
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expression.property.type === 'Literal'
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? String(expression.property.value)
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: expression.property.name
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);
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expression = expression.object;
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}
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// Check for "frontmatter.[ANYTHING]".
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if (expression.type !== 'Identifier' || expression.name !== 'frontmatter') return new Error();
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return expressionPath.reverse();
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}
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function getMdxFrontmatterVariableValue(astroData: MarkdownAstroData, path: string[]) {
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let value: MdxFrontmatterVariableValue = astroData.frontmatter;
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for (const key of path) {
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if (!value[key]) return undefined;
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value = value[key];
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}
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return value;
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}
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function isMdxTextExpression(node: Node): node is MdxTextExpression {
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return node.type === 'mdxTextExpression';
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}
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type MdxFrontmatterVariableValue =
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MarkdownAstroData['frontmatter'][keyof MarkdownAstroData['frontmatter']];
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