deno.land / std@0.166.0 / encoding / front_matter / mod.ts
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/** * {@linkcode createExtractor}, {@linkcode recognize} and {@linkcode test} functions * to handle many forms of front matter. * * Adapted from * [jxson/front-matter](https://github.com/jxson/front-matter/blob/36f139ef797bd9e5196a9ede03ef481d7fbca18e/index.js). * * @module */
type Delimiter = string | [begin: string, end: string];export type Parser = <T = Record<string, unknown>>(str: string) => T;export type Extractor = <T = Record<string, unknown>>( str: string,) => Extract<T>;
export enum Format { YAML = "yaml", TOML = "toml", JSON = "json", UNKNOWN = "unknown",}
export type Extract<T> = { frontMatter: string; body: string; attrs: T;};
const { isArray } = Array;const [RX_RECOGNIZE_YAML, RX_YAML] = createRegExp( ["---yaml", "---"], "= yaml =", "---",);const [RX_RECOGNIZE_TOML, RX_TOML] = createRegExp( ["---toml", "---"], "= toml =",);const [RX_RECOGNIZE_JSON, RX_JSON] = createRegExp( ["---json", "---"], "= json =",);const MAP_FORMAT_TO_RECOGNIZER_RX: Omit< Record<Format, RegExp>, Format.UNKNOWN> = { [Format.YAML]: RX_RECOGNIZE_YAML, [Format.TOML]: RX_RECOGNIZE_TOML, [Format.JSON]: RX_RECOGNIZE_JSON,};const MAP_FORMAT_TO_EXTRACTOR_RX: Omit<Record<Format, RegExp>, Format.UNKNOWN> = { [Format.YAML]: RX_YAML, [Format.TOML]: RX_TOML, [Format.JSON]: RX_JSON, };
function getBeginToken(delimiter: Delimiter): string { return isArray(delimiter) ? delimiter[0] : delimiter;}
function getEndToken(delimiter: Delimiter): string { return isArray(delimiter) ? delimiter[1] : delimiter;}
function createRegExp(...dv: Delimiter[]): [RegExp, RegExp] { const beginPattern = "(" + dv.map(getBeginToken).join("|") + ")"; const pattern = "^(" + "\\ufeff?" + // Maybe byte order mark beginPattern + "$([\\s\\S]+?)" + "^(?:" + dv.map(getEndToken).join("|") + ")\\s*" + "$" + (Deno.build.os === "windows" ? "\\r?" : "") + "(?:\\n)?)";
return [ new RegExp("^" + beginPattern + "$", "im"), new RegExp(pattern, "im"), ];}
function _extract<T>( str: string, rx: RegExp, parse: Parser,): Extract<T> { const match = rx.exec(str); if (!match || match.index !== 0) { throw new TypeError("Unexpected end of input"); } const frontMatter = match.at(-1)?.replace(/^\s+|\s+$/g, "") || ""; const attrs = parse(frontMatter) as T; const body = str.replace(match[0], ""); return { frontMatter, body, attrs };}
/** * Factory that creates a function that extracts front matter from a string with the given parsers. * Supports YAML, TOML and JSON. * * @param formats A descriptor containing Format-parser pairs to use for each format. * @returns A function that extracts front matter from a string with the given parsers. * * ```ts * import { createExtractor, Format, Parser } from "https://deno.land/std@$STD_VERSION/encoding/front_matter/mod.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * import { parse as parseYAML } from "https://deno.land/std@$STD_VERSION/encoding/yaml.ts"; * import { parse as parseTOML } from "https://deno.land/std@$STD_VERSION/encoding/toml.ts"; * const extractYAML = createExtractor({ [Format.YAML]: parseYAML as Parser }); * const extractTOML = createExtractor({ [Format.TOML]: parseTOML as Parser }); * const extractJSON = createExtractor({ [Format.JSON]: JSON.parse as Parser }); * const extractYAMLOrJSON = createExtractor({ * [Format.YAML]: parseYAML as Parser, * [Format.JSON]: JSON.parse as Parser, * }); * * let { attrs, body, frontMatter } = extractYAML<{ title: string }>("---\ntitle: Three dashes marks the spot\n---\nferret"); * assertEquals(attrs.title, "Three dashes marks the spot"); * assertEquals(body, "ferret"); * assertEquals(frontMatter, "title: Three dashes marks the spot"); * * ({ attrs, body, frontMatter } = extractTOML<{ title: string }>("---toml\ntitle = 'Three dashes followed by format marks the spot'\n---\n")); * assertEquals(attrs.title, "Three dashes followed by format marks the spot"); * assertEquals(body, ""); * assertEquals(frontMatter, "title = 'Three dashes followed by format marks the spot'"); * * ({ attrs, body, frontMatter } = extractJSON<{ title: string }>("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\ngoat")); * assertEquals(attrs.title, "Three dashes followed by format marks the spot"); * assertEquals(body, "goat"); * assertEquals(frontMatter, "{\"title\": \"Three dashes followed by format marks the spot\"}"); * * ({ attrs, body, frontMatter } = extractYAMLOrJSON<{ title: string }>("---\ntitle: Three dashes marks the spot\n---\nferret")); * assertEquals(attrs.title, "Three dashes marks the spot"); * assertEquals(body, "ferret"); * assertEquals(frontMatter, "title: Three dashes marks the spot"); * * ({ attrs, body, frontMatter } = extractYAMLOrJSON<{ title: string }>("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\ngoat")); * assertEquals(attrs.title, "Three dashes followed by format marks the spot"); * assertEquals(body, "goat"); * assertEquals(frontMatter, "{\"title\": \"Three dashes followed by format marks the spot\"}"); * ``` */export function createExtractor( formats: Partial<Record<Format, Parser>>,): Extractor { const formatKeys = Object.keys(formats) as Format[];
return function extract<T>(str: string): Extract<T> { const format = recognize(str, formatKeys); const parser = formats[format];
if (format === Format.UNKNOWN || !parser) { throw new TypeError(`Unsupported front matter format`); }
return _extract(str, MAP_FORMAT_TO_EXTRACTOR_RX[format], parser); };}
/** * Tests if a string has valid front matter. Supports YAML, TOML and JSON. * * @param str String to test. * @param formats A list of formats to test for. Defaults to all supported formats. * * ```ts * import { test, Format } from "https://deno.land/std@$STD_VERSION/encoding/front_matter/mod.ts"; * import { assert } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * * assert(test("---\ntitle: Three dashes marks the spot\n---\n")); * assert(test("---toml\ntitle = 'Three dashes followed by format marks the spot'\n---\n")); * assert(test("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\n")); * * assert(!test("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\n", [Format.YAML])); * ``` */export function test(str: string, formats?: Format[]): boolean { if (!formats) { formats = Object.keys(MAP_FORMAT_TO_EXTRACTOR_RX) as Format[]; }
for (const format of formats) { if (format === Format.UNKNOWN) { throw new TypeError("Unable to test for unknown front matter format"); }
const match = MAP_FORMAT_TO_EXTRACTOR_RX[format].exec(str); if (match?.index === 0) { return true; } }
return false;}
/** * Recognizes the format of the front matter in a string. Supports YAML, TOML and JSON. * * @param str String to recognize. * @param formats A list of formats to recognize. Defaults to all supported formats. * * ```ts * import { recognize, Format } from "https://deno.land/std@$STD_VERSION/encoding/front_matter/mod.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * * assertEquals(recognize("---\ntitle: Three dashes marks the spot\n---\n"), Format.YAML); * assertEquals(recognize("---toml\ntitle = 'Three dashes followed by format marks the spot'\n---\n"), Format.TOML); * assertEquals(recognize("---json\n{\"title\": \"Three dashes followed by format marks the spot\"}\n---\n"), Format.JSON); * assertEquals(recognize("---xml\n<title>Three dashes marks the spot</title>\n---\n"), Format.UNKNOWN); * * assertEquals(recognize("---json\n<title>Three dashes marks the spot</title>\n---\n", [Format.YAML]), Format.UNKNOWN); */function recognize(str: string, formats?: Format[]): Format { if (!formats) { formats = Object.keys(MAP_FORMAT_TO_RECOGNIZER_RX) as Format[]; }
const [firstLine] = str.split(/(\r?\n)/);
for (const format of formats) { if (format === Format.UNKNOWN) { continue; }
if (MAP_FORMAT_TO_RECOGNIZER_RX[format].test(firstLine)) { return format; } }
return Format.UNKNOWN;}
std
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a year ago
