83 lines
2.2 KiB
JavaScript
83 lines
2.2 KiB
JavaScript
// Limited implementation of python % string operator, supports only %s and %r for now
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// (other formats are not used here, but may appear in custom templates)
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'use strict';
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const { inspect } = require('util');
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module.exports = function sub(pattern, ...values) {
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let regex = /%(?:(%)|(-)?(\*)?(?:\((\w+)\))?([A-Za-z]))/g;
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let result = pattern.replace(
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regex,
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function (_, is_literal, is_left_align, is_padded, name, format) {
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if (is_literal) return '%';
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let padded_count = 0;
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if (is_padded) {
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if (values.length === 0)
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throw new TypeError('not enough arguments for format string');
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padded_count = values.shift();
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if (!Number.isInteger(padded_count)) throw new TypeError('* wants int');
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}
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let str;
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if (name !== undefined) {
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let dict = values[0];
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if (typeof dict !== 'object' || dict === null)
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throw new TypeError('format requires a mapping');
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if (!(name in dict)) throw new TypeError(`no such key: '${name}'`);
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str = dict[name];
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} else {
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if (values.length === 0)
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throw new TypeError('not enough arguments for format string');
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str = values.shift();
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}
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switch (format) {
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case 's':
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str = String(str);
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break;
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case 'r':
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str = inspect(str);
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break;
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case 'd':
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case 'i':
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if (typeof str !== 'number') {
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throw new TypeError(
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`%${format} format: a number is required, not ${typeof str}`
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);
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}
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str = String(str.toFixed(0));
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break;
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default:
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throw new TypeError(`unsupported format character '${format}'`);
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}
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if (padded_count > 0) {
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return is_left_align ?
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str.padEnd(padded_count)
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: str.padStart(padded_count);
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} else {
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return str;
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}
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}
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);
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if (values.length) {
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if (
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values.length === 1 &&
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typeof values[0] === 'object' &&
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values[0] !== null
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) {
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// mapping
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} else {
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throw new TypeError(
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'not all arguments converted during string formatting'
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);
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}
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}
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return result;
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};
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