extract-pot.js

/*
Creates src/locale/po/template.pot by scanning the application source.
*/

'use strict';
const acorn = require('acorn');
const estraverse = require('estraverse');
const fs = require('fs');
const htmlParser = require('htmlparser2');
const glob = require('glob');
const poFile = require('pofile');

let result = new poFile();

function addItem(location, string, pluralString, comment) {
	/*
	Clean up the comment.
	*/

	if (comment) {
		comment = comment.trim().replace(/[\t\r\n]+/g, ' ');
	}

	/*
	Check for an existing item.
	*/

	let existing = result.items.find(item => item.msgid === string);

	if (existing) {
		existing.references.push(location);

		if (comment) {
			existing.extractedComments.push(comment);
		}
	}
	else {
		let item = new poFile.Item();

		item.msgid = string;
		item.msgid_plural = pluralString;
		item.references = [location];

		if (pluralString) {
			item.msgstr = ['', ''];
		}

		if (comment) {
			item.extractedComments = [comment];
		}

		result.items.push(item);
	}
}

/*
Parse .html files for text in this format: 
{{ 'Simple string' | say }}
{{ 'Singular string' | sayPlural 'Plural string' }} 
*/

const templateRegexp = new RegExp(
	/* Opening moustache. */
	/{{{? */.source +

	/* String to localize and say filter. */
	/['"]([^}]*?)['"] *\| *say/.source +

	/* Optional pluralization. */
	/(?:Plural *['"](.+)['"].*)?/.source +

	/* Closing moustache. */
	/ *}}}?/.source,

	'gm'
);

glob.sync('src/**/*.html').forEach(fileName => {
	const source = fs.readFileSync(fileName, { encoding: 'utf8' });
	const parser = new htmlParser.Parser({
		ontext(text) {
			let match;

			while (match = templateRegexp.exec(text.trim())) {
				/*
				The first captured expression is a comment, if any.
				The third is the plural form of the string, if any.
				*/

				addItem(fileName, match[1], match[2]);
			}
		}
	});

	parser.write(source);
});

/*
Parse .js files for say() and sayPlural() calls.
*/

glob.sync('src/**/*.js').forEach(fileName => {
	/*
	Simplifies an expression (e.g. 'a compound ' + ' string') to a single
	value.
	*/

	function parseValue(node) {
		switch (node.type) {
			case 'Literal':
				/*
				We can't use .value here because we need to keep the strings
				intact with Unicode escapes.
				*/
				
				return node.raw.replace(/^['"]/, '').replace(/['"]$/, '');
			break;

			case 'BinaryExpression':
				if (node.operator === '+') {
					return parseValue(node.left) + parseValue(node.right);
				}

				throw new Error(
					`Don't know how to parse operator ${node.operator}`
				);
			break;

			default:
				throw new Error(`Don't know how to parse value of ${node.type}`);
		}
	}

	let comments = [];
	const ast = acorn.parse(
		fs.readFileSync(fileName, { encoding: 'utf8' }),
		{
			ecmaVersion: 6,
			locations: true,
			onComment: comments
		}
	);

	estraverse.traverse(
		ast,
		{
			enter: function(node, parent) {
				if (node.type === 'CallExpression') {
					let funcName;

					if (node.callee.type === 'Identifier') {
						funcName = node.callee.name;
					}
					else if (node.callee.type === 'MemberExpression') {
						funcName = node.callee.property.name;
					}

					/*
					Check for a comment that ended 0-2 lines before this call.
					*/

					const precedingComment = comments.find(comment =>
						Math.abs(comment.loc.end.line - node.loc.start.line) < 3 &&
						/^\s*L10n/.test(comment.value)
					);

					if (funcName === 'say') {
						addItem(
							fileName + ':' + node.loc.start.line,
							parseValue(node.arguments[0]),
							null,
							precedingComment ? precedingComment.value : null
						);
					}

					if (funcName === 'sayPlural') {
						addItem(
							fileName + ':' + node.loc.start.line,
							parseValue(node.arguments[0]),
							parseValue(node.arguments[1]),
							precedingComment ? precedingComment.value : null
						);
					}
				}
			}
		}
	);
});

fs.writeFileSync(
	'src/locale/po/template.pot',
	result.toString(),
	{ encoding: 'utf8' }
);
console.log(`Wrote ${result.items.length} extracted strings to src/locale/po/template.pot.\n`);