apg-js

JavaScript APG

4.2.1 Release Notes

Some ABNF grammar authors will use zero repetitions as an explicit empty string acceptor. That is, one or the other of something like,

char = %d33-127 empty1 = 0char empty2 = 0"x"

Previous version of APG have rejected zero repititions as an empty string acceptor in favor of the more intuitive and simpler to produce and simpler to process empty literal string

empty = ""

apg-js version 4.2.0 and lower neglects to reject the zero repetitions form and, unfortunately, it only sometimes actually accepts an empty string and sometimes fails. Version 4.2.1 corrects this. Zero repetitions are allowed as explicit empty string acceptors and are processed correctly.

Note, however, that zero repetitions is deprecated in that not all implementations of APG accept it and that is it is slightly less efficient to implement. Favored is the more streamlined empty literal string, ""

4.2.0 Release Notes

Version 4.2.0 fixes some issues that have been causing problems for some bundlers and/or development tools. ./src/apg-conv-api/converter.js, ./src/apg-conv-api/transformers.js and ./src/apg-lib/utilities.js now refer explicitly to the exported functions rather than relying on a saved copy of the this reference. Also, use of the global Buffer object has been replaced with

const { Buffer } = require('buffer');

and similary for fs and other global node.js properties, as recommended in the Node.js v20.5.1 documentation. (Note that require('node:buffer') causes problems with using browerify to bundle the libraries for web page use. Removing the node: prefix solves that problem without causing problems with the bundle usage. Thanks to contributions in the GitHub issue #13 thread for this suggestion.)

This updated version of apg-js has been tested with all of the examples in apg-js-examples. All examples including the web page examples work as expected.

Also, all dependencies have been moved to devDependencies, removing the need for any globally installed packages.

Overview

apg-js is the JavaScript version of APG, an ABNF Parser Generator. APG generates recursive-descent parsers directly from a superset of ABNF (SABNF). Visit the APG website for a complete overview of APG and SABNF.

apg-js obsoletes apg-js2, apg-js2-lib, apg-js2-exp, apg-js2-api, apg-conv and apg-conv-api. It changes them in two significant ways.

• It fixes a major problem in the attributes algorithm. Previous versions could fail on large grammars with many or large sets of mutually-recursive rules.
• It combines all of those packages into a single, easier to manage and maintain package.

Documentation

This package is meant to assist other parsing applications and is normally not installed by itself, rather installed along with those other applications. For details and many examples of using of the libraries, both in node.js and browser web page applications, see apg-js-examples at GitHub or npmjs. However, it does provide access to two, node.js applications, apg and apg-conv.

Applications

apg is the parser generator. To see its usage run,

npm run apg -- --help

apg-conv is a data conversion application. To see its usage run,

npm run apg-conv -- --help

Libraries

This package contains four libraries that can be used in either node.js or browser applications. The libraries depend upon one another and the dependency tree looks like so:

apg-exp
|- apg-api
|-|- apg-lib
|-|-|- apg-conv-api

Each of the libraries is bundled for browser use along with some special styles. Each bundle contains all of its dependencies explicitly. That is, if a browser application needs both apg-api and apg-lib, only the apg-api bundle need be scripted into the page.

The library and css bundles are in the ./dist directory.

./dist/apg-exp-bundle.js
./dist/apg-api-bundle.js
./dist/apg-lib-bundle.js
./dist/apg-conv-api-bundle.js
./dist/apg-lib-bundle.css

The bundles can all be regenerated with the scripts:

npm run bundle-apg-conv-api
npm run bundle-apg-lib
npm run bundle-apg-api
npm run bundle-apg-exp
npm run bundle-apg-lib-css

Code Documentation

The code documentation is in docco format and can be generated with:

npm run docco

The documentation is then at ./docs/index.html or see it here at the APG website.