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import yaml from 'js-yaml';
export function isFrontmatterValid(frontmatter: Record<string, any>) {
try {
// ensure frontmatter is JSON-serializable
JSON.stringify(frontmatter);
} catch {
return false;
}
return typeof frontmatter === 'object' && frontmatter !== null;
}
const frontmatterRE = /^---(.*?)^---/ms;
export function extractFrontmatter(code: string): string | undefined {
return frontmatterRE.exec(code)?.[1];
}
export interface ParseFrontmatterOptions {
/**
* How the frontmatter should be handled in the returned `content` string.
* - `preserve`: Keep the frontmatter.
* - `remove`: Remove the frontmatter.
* - `empty-with-spaces`: Replace the frontmatter with empty spaces. (preserves sourcemap line/col/offset)
* - `empty-with-lines`: Replace the frontmatter with empty line breaks. (preserves sourcemap line/col)
*
* @default 'remove'
*/
frontmatter: 'preserve' | 'remove' | 'empty-with-spaces' | 'empty-with-lines';
}
export interface ParseFrontmatterResult {
frontmatter: Record<string, any>;
rawFrontmatter: string;
content: string;
}
export function parseFrontmatter(
code: string,
options?: ParseFrontmatterOptions,
): ParseFrontmatterResult {
const rawFrontmatter = extractFrontmatter(code);
if (rawFrontmatter == null) {
return { frontmatter: {}, rawFrontmatter: '', content: code };
}
const parsed = yaml.load(rawFrontmatter);
const frontmatter = (parsed && typeof parsed === 'object' ? parsed : {}) as Record<string, any>;
let content: string;
switch (options?.frontmatter ?? 'remove') {
case 'preserve':
content = code;
break;
case 'remove':
content = code.replace(`---${rawFrontmatter}---`, '');
break;
case 'empty-with-spaces':
content = code.replace(
`---${rawFrontmatter}---`,
` ${rawFrontmatter.replace(/[^\r\n]/g, ' ')} `,
);
break;
case 'empty-with-lines':
content = code.replace(`---${rawFrontmatter}---`, rawFrontmatter.replace(/[^\r\n]/g, ''));
break;
}
return {
frontmatter,
rawFrontmatter,
content,
};
}
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