Banner string duplicates on watchify rebundle

[cguinnup]

Thanks for the plugin, I especially appreciate the source map support.

I'm adding a simple string banner and performing incremental rebundles with watchify. On the first bundling, everything is correct. After changing source code & triggering subsequent rebundles, there are suddenly duplicate instances of the banner string. This duplication causes an error when the script runs.

I believe my use of browserify-banner is correct:

let scriptBundler = browserify({
    entries: entry + '.js',
    basedir: buildDir,
    debug: devMode,  // Source maps!
    cache: {},         // For watchify's incremental bundling 
    packageCache: {},  // "
    fullPaths: false,  // "
    noParse: ['jquery'], // No require() in this big lib: save time & don't parse
    browserField: false,              // Makes bundle runnable in Node
    builtins: false,                  // "
    commondir: false,                 // "
    insertGlobalVars: {               // "
        Buffer: undefined,            // "
        'Buffer.isBuffer': undefined, // "
        global: undefined,            // "
        process: undefined            // "
    },                               
});

// Make the Node script runnable in the shell
let scriptHeader = '#!/usr/bin/env node\n';
if (devMode) {
    // Make Node show source code in stack traces
    scriptHeader += 'require("source-map-support").install();\n';
    scriptBundler.plugin(watchify);
}
scriptBundler.plugin(banner, {banner: scriptHeader});

// The rebundle process
const rebundle = function () {
    var start = Date.now();
    console.log('Bundling "' + entry + '"');
    return scriptBundler.bundle()
      .pipe(vinylStream(entry))
      .pipe(gulpif(!devMode && !argv['skip-minify'], vinylBuffer()))
      .pipe(gulpif(!devMode && !argv['skip-minify'], uglify()))
      .pipe(chmod({ execute: true }))
      .pipe(gulp.dest(distDir))
      .pipe(notify(function() {
        console.log('Bundled  "' + entry + '" in ' + (Date.now() - start) / 1000 + ' s');
      }));
};

// Watch for changes while developing
if (devMode) {
    scriptBundler.on('update', rebundle);
}

[cguinnup]

Removing browserify-banner's line 32 browserify.on('reset', wrapBundle); seems to fix the issue

[JamesMessinger]

Hi. Thanks for opening this issue. I don't use watchify very often, so I've never run into this myself. But your analysis makes sense.

I know that the "reset" event is needed in some cases, so I don't feel comfortable completely removing it. Maybe we can add logic to detect if it's being run in a watchify process and, if so, then not listen for that event.

[cguinnup]

According to Browserify docs, the reset event seems to be called between multiple bundle() invocations. Since your bundle() invocation already prepends the banner, it doesn't appear that a reset event should be necessary, unless you have cleanup to perform in between bundlings.

[JamesMessinger]

Hmmm... ok. It's possible that I'm wrong and the "reset" event is entirely unnecessary. Do all the tests still pass if you remove line 32? If so, then I'll gladly accept a PR.