index.js

#!/usr/bin/env node
'use strict';

const pkg = require('./package.json');
const fs = require('fs');
const path = require('path');
const execSync = require('child_process').execSync;

function list(val) {
    return val.split(',');
}

function process_command(command, filename) {
    command = command + ' ' + filename;
    return (execSync(command)).toString();
}

var program = require('commander');

program
.version(pkg.version)
.arguments('<file>')
.option('--cond <cond>', 'A comma separated list of conditional names: --cond debug,prod,staging', list, [])
.action(function(file) {
    program.file = file;
})
.parse(process.argv);

var conditionals = [];
var use_conditionals = false;

if (!program.file || !program.file.length){
    program.help();
    process.exit(8);
} else if (!fs.existsSync(program.file)) {
    console.error("The input file could not be found.");
    process.exit(1);
} else {
    conditionals = program.cond || [];
    program.file = fs.realpathSync(program.file);
    if (conditionals.length){
        use_conditionals = true;
    }
}

const openTag = '<!partial';
const condAttr = 'cond';
const srcAttr = 'src';
const cmdAttr = 'run';
const cmdCondAttr = 'run-cond';

var contents = fs.readFileSync(program.file).toString();
var filepath = path.dirname(program.file);
var found = 0;

function get_attrib(partial, attrib) {
    attrib = ' ' + attrib + '=';
    var attrib_len = attrib.length;
    var start = partial.indexOf(attrib);
    if (start === -1) {
        return null;
    }
    start += attrib_len;
    var quoteType = partial.charAt(start);
    start ++;
    return partial.slice(start, partial.indexOf(quoteType, start))
}

function has_cond(conds) {
    conds = list(conds);
    var len = conds.length;
    if (len > 0) {
        for (var x = 0; x < len; x++) {
            if (conditionals.indexOf(conds[x]) != -1) {
                return true;
            }
        }
    }
    return false;
}

while (found !== -1) {
    found = contents.indexOf(openTag, found);
    if (found === -1) {
        continue;
    }
    var end = contents.indexOf('>', found) + 1;
    if (contents.charAt(end) === "\n") {
        end++;
    }
    var partial = contents.slice(found, end).toString();
    if (use_conditionals === true) {
        var conds = get_attrib(partial, condAttr);
        if (conds !== null) {
            if (!has_cond(conds)) {
                contents = contents.replace(partial, "");
                continue;
            }
        }
    }
    var src = get_attrib(partial, srcAttr);
    var cmd = get_attrib(partial, cmdAttr);
    var cmdCond = get_attrib(partial, cmdCondAttr);
    var partial_contents = '';
    if (src !== null) {
        if (!path.isAbsolute(src)) {
            src = path.normalize(filepath + '/' + src);
        }
        if (fs.existsSync(src) && src !== program.file) {
            if (cmd !== null) {
                if (use_conditionals && cmdCond !== null) {
                    if (has_cond(cmdCond)){
                        partial_contents = process_command(cmd, src);
                    } else {
                        partial_contents = fs.readFileSync(src).toString();
                    }
                } else {
                    partial_contents = process_command(cmd, src);
                }
            } else {
                partial_contents = fs.readFileSync(src).toString();
            }
        }
    }
    contents = contents.replace(partial, partial_contents);
}
process.stdout.write(contents);