prettier-plugin-askama-template/src/printer.ts

import { Printer } from "prettier";
import { builders, utils } from "prettier/doc";
import {
	Placeholder,
	Node,
	Expression,
	Statement,
	Block,
	IgnoreBlock,
} from "./jinja";

const NOT_FOUND = -1;

process.env.PRETTIER_DEBUG = "true";

export const print: Printer<Node>["print"] = (path) => {
	const node = path.getNode();
	if (!node) {
		return [];
	}

	switch (node.type) {
		case "expression":
			return printExpression(node as Expression);
		case "statement":
			return printStatement(node as Statement);
		case "ignore":
			return printIgnoreBlock(node as IgnoreBlock);
	}
	return [];
};

const printExpression = (node: Expression): builders.Doc => {
	return builders.group(["{{", " ", node.content, " ", "}}"], {
		shouldBreak: node.ownLine || node.content.includes("\n"),
	});
};

const printStatement = (node: Statement): builders.Doc => {
	const statemnt = builders.group(
		[
			"{%",
			node.startDelimiter,
			" ",
			node.content,
			" ",
			node.endDelimiter,
			"%}",
		],
		{ shouldBreak: true }
	);

	return node.keyword === "else"
		? [builders.dedent(builders.hardline), statemnt, builders.hardline]
		: statemnt;
};

const printIgnoreBlock = (node: IgnoreBlock): builders.Doc => {
	return builders.group(node.content, { shouldBreak: node.ownLine });
};

export const embed: Printer<Node>["embed"] = (
	path,
	print,
	textToDoc,
	options
) => {
	const node = path.getNode();
	if (!node || !["root", "block"].includes(node.type)) {
		return null;
	}

	const mapped = splitAtElse(node).map((content) => {
		let doc;
		if (content in node.nodes) {
			doc = content;
		} else {
			doc = utils.stripTrailingHardline(
				textToDoc(content, {
					...options,
					parser: "html",
				})
			);
		}

		let ignoreDoc = false;

		return utils.mapDoc(doc, (currentDoc) => {
			if (typeof currentDoc !== "string") {
				return currentDoc;
			}

			if (currentDoc === "<!-- prettier-ignore -->") {
				ignoreDoc = true;
				return currentDoc;
			}

			const idxs = findPlaceholders(currentDoc).filter(
				([start, end]) => currentDoc.slice(start, end + 1) in node.nodes
			);
			if (!idxs.length) {
				return currentDoc;
			}

			const res: builders.Doc = [];
			let lastEnd = 0;
			for (const [start, end] of idxs) {
				if (lastEnd < start) {
					res.push(currentDoc.slice(lastEnd, start));
				}

				const p = currentDoc.slice(start, end + 1) as string;

				if (ignoreDoc) {
					res.push(node.nodes[p].originalText);
				} else {
					res.push(path.call(print, "nodes", p));
				}

				lastEnd = end + 1;
			}

			if (lastEnd > 0 && currentDoc.length > lastEnd) {
				res.push(currentDoc.slice(lastEnd));
			}

			ignoreDoc = false;
			return res;
		});
	});

	if (node.type === "block") {
		return builders.group([
			path.call(print, "nodes", (node as Block).start.id),
			builders.indent([builders.softline, utils.stripTrailingHardline(mapped)]),
			builders.hardline,
			path.call(print, "nodes", (node as Block).end.id),
		]);
	}
	return [...mapped, builders.hardline];
};

const splitAtElse = (node: Node): string[] => {
	const elseNodes = Object.values(node.nodes).filter(
		(n) =>
			n.type === "statement" &&
			(n as Statement).keyword === "else" &&
			node.content.search(n.id) !== NOT_FOUND
	);
	if (!elseNodes.length) {
		return [node.content];
	}

	const re = new RegExp(`(${elseNodes.map((e) => e.id).join(")|(")})`);
	return node.content.split(re).filter(Boolean);
};

/**
 * Returns the indexs of the first and the last character of any placeholder
 * occuring in a string.
 */
export const findPlaceholders = (text: string): [number, number][] => {
	const res = [];
	let i = 0;

	while (true) {
		const start = text.slice(i).search(Placeholder.startToken);
		if (start === NOT_FOUND) break;
		const end = text
			.slice(start + i + Placeholder.startToken.length)
			.search(Placeholder.endToken);
		if (end === NOT_FOUND) break;

		res.push([
			start + i,
			end + start + i + Placeholder.startToken.length + 1,
		] as [number, number]);
		i += start + Placeholder.startToken.length;
	}
	return res;
};