peggy-tag

Tagged template strings for Peggy grammars

Installation

npm install peggy-tag

Usage

import peggy from "peggy-tag";

const parse = peggy`foo = $("f" "o"+)`;
console.log(parse("foooo")); // "foooo"

const traceGrammar = peggy.withOptions({ trace: true });
const trace = traceGrammar`num = n:$[0-9]+ { return parseInt(n, 10); }`
console.log(trace("123"));
// 8:20-8:20 rule.enter num
// 8:20-8:23 rule.match num
// 123

If your grammar imports rules from other grammars, you MUST use the async functions withImports or withImportsOptions

import {withImports, withImportsOptions} from "peggy-tag";

const parse = await withImports`
import Foo from './test/fixtures/foo.js'
bar = Foo`;
console.log(parse("foo")); // "foo"

const traceGrammar = await withImportsOptions({ trace: true });
const trace = traceGrammar`num = n:$[0-9]+ { return parseInt(n, 10); }`
console.log(trace("123"));
// 11:20-11:20 rule.enter num
// 11:20-11:23 rule.match num
// 123

Notes:

• This currently is only tested on Node 18+, no browser version yet.
• Node 20.8+ and --experimental-vm-modules are required for the async versions that allow importing libraries.
• This is for NON-performance-sensitive code (e.g. prototypes), because the parser with be generated every time the template is evaluated.
• If your parse function's variable name has exactly five letters (like "parse" or "trace"), the column numbers will be correct. See issue #14 for discussion.