prettier-plugin-jinja-template/src/parser.ts

Prettier plugin for formatting jinja templates.

import { Parser } from "prettier";
import {
	BlockNode,
	Delimiter,
	Node,
	Placeholder,
	RootNode,
	StatementNode,
} from "./jinja";
import regex from "./regex";

const NOT_FOUND = -1;

export const parse: Parser<Node>["parse"] = (text) => {
	const statementStack: StatementNode[] = [];

	const root: RootNode = {
		id: "0",
		type: "root",
		content: text,
		preNewLines: 0,
		originalText: text,
		index: 0,
		length: 0,
		nodes: {},
	};

	const generatePlaceholder = placeholderGenerator(text);

	let match;
	let i = 0;
	while ((match = root.content.slice(i).match(regex)) !== null) {
		if (!match.groups || match.index === undefined) {
			continue;
		}
		const matchLength = match[0].length;

		// skip script and style blocks
		if (match.groups.scriptBlock || match.groups.styleBlock) {
			i += match.index + matchLength;
			continue;
		}

		const matchText = match.groups.node;
		const expression = match.groups.expression;
		const statement = match.groups.statement;
		const ignoreBlock = match.groups.ignoreBlock;
		const comment = match.groups.comment;

		if (!matchText && !expression && !statement && !ignoreBlock && !comment) {
			continue;
		}
		const placeholder = generatePlaceholder();

		const emptyLinesBetween = root.content
			.slice(i, i + match.index)
			.match(/^\s+$/) || [""];
		const preNewLines = emptyLinesBetween.length
			? emptyLinesBetween[0].split("\n").length - 1
			: 0;

		const node = {
			id: placeholder,
			preNewLines,
			originalText: matchText,
			index: match.index + i,
			length: matchText.length,
			nodes: root.nodes,
		};

		if (comment != undefined || ignoreBlock != undefined) {
			root.content = replaceAt(
				root.content,
				placeholder,
				match.index + i,
				matchLength,
			);
			root.nodes[node.id] = {
				...node,
				type: comment ? "comment" : "ignore",
				content: comment || ignoreBlock,
			};

			i += match.index + placeholder.length;
		}

		if (expression != undefined) {
			const delimiter = {
				start: match.groups.startDelimiterEx,
				end: match.groups.endDelimiterEx,
			} as Delimiter;

			root.content = replaceAt(
				root.content,
				placeholder,
				match.index + i,
				matchLength,
			);
			root.nodes[node.id] = {
				...node,
				type: "expression",
				content: expression,
				delimiter,
			};

			i += match.index + placeholder.length;
		}

		if (statement != undefined) {
			const keyword = match.groups.keyword;
			const delimiter = {
				start: match.groups.startDelimiter,
				end: match.groups.endDelimiter,
			} as Delimiter;

			if (keyword.startsWith("end")) {
				let start: StatementNode | undefined;
				while (!start) {
					start = statementStack.pop();

					if (!start) {
						throw new Error(
							`No opening statement found for closing statement "{% ${statement} %}".`,
						);
					}

					if (keyword.replace(/end_?/, "") !== start.keyword) {
						root.content = replaceAt(
							root.content,
							start.id,
							start.index,
							start.length,
						);
						i += start.id.length - start.length;

						start = undefined;
						continue;
					}
				}

				const end: StatementNode = {
					...node,
					index: match.index + i,
					type: "statement",
					content: statement,
					keyword,
					delimiter,
				};
				root.nodes[end.id] = end;

				const originalText = root.content.slice(
					start.index,
					end.index + end.length,
				);
				const block: BlockNode = {
					id: generatePlaceholder(),
					type: "block",
					start: start,
					end: end,
					content: originalText.slice(
						start.length,
						originalText.length - end.length,
					),
					preNewLines: start.preNewLines,
					containsNewLines: originalText.search("\n") !== NOT_FOUND,
					originalText,
					index: start.index,
					length: end.index + end.length - start.index,
					nodes: root.nodes,
				};
				root.nodes[block.id] = block;

				root.content = replaceAt(
					root.content,
					block.id,
					start.index,
					originalText.length,
				);

				i += match.index + block.id.length + end.length - originalText.length;
			} else {
				root.nodes[node.id] = {
					...node,
					type: "statement",
					content: statement,
					keyword,
					delimiter,
				};
				statementStack.push(root.nodes[placeholder] as StatementNode);

				i += match.index + matchLength;
			}
		}
	}

	for (const stmt of statementStack) {
		root.content = root.content.replace(stmt.originalText, stmt.id);
	}

	return root;
};

const placeholderGenerator = (text: string) => {
	let id = 0;

	return (): string => {
		while (true) {
			id++;

			const placeholder = Placeholder.startToken + id + Placeholder.endToken;
			if (!text.includes(placeholder)) {
				return placeholder;
			}
		}
	};
};

const replaceAt = (
	str: string,
	replacement: string,
	start: number,
	length: number,
): string => {
	return str.slice(0, start) + replacement + str.slice(start + length);
};