live-patch

patch the source code of a running program

Currently this module is nothing more than cheap parlor tricks.

Whether any module claiming these features can ever be more than flimsy cardboard is an open question.

example

First whip up a patch.js to monitor a program.js file for changes:

var fs = require('fs');
var gaze = require('gaze');
var file = __dirname + '/program.js';
 
var patch = require('live-patch')();
 
gaze(file, function (err, w) {
    w.on('changed', function (p) { read() });
});
read();
 
function read () {
    fs.readFile(file, 'utf8', function (err, src) {
        if (err) return console.error(err);
        patch.update(src);
    });
}

run patch.js and then then edit program.js live and watch the output.

methods

var patch = require('live-patch')

var p = patch(src)

Create a patch instance p, optionally with some source code src.

p.update(src)

Set the source code to src, updating the running state as necessary.

usage

This package comes with a command-line tool.

live-patch {OPTIONS} FILE [ARGS...]

  Run FILE with node, watching for changes.
  When FILE changes, the new source is patched in.

  -h --help  Show this message.

todo

I'm not especially keen to develop this prototype much further, but if somebody wants, these features would lead to a more robust tool:

• create a dependency graph for AST updates - when you update var x, you also implicitly update var y = x + 10 and so on.

As it stands this demo is already pushing the limits of what undisciplined AST trickery is reasonably capable of.

install

With npm do:

npm install live-patch

to get the library or

npm install -g live-patch

to get the command-line tool.

license

MIT