assert.js

var bemxjst = require('./');
var bemhtml = bemxjst.bemhtml;

// Add templates
var templates = bemhtml.compile(function() {
  // true/false в аттрибутах
  block('*').def()(function() {
    var ret = applyNext();

    var ctx = this.ctx;
    var attrs = ctx.attrs;
    if (attrs) {
      Object.keys(attrs).forEach(function(key) {
        if (typeof attrs[key] === 'boolean') {
          console.warn(
            '\nWARNING: boolean attribute value:',
            attrs[key],
            'in BEMJSON:',
            ctx
          );
          console.warn('Notice what bem-xjst behaviour changed: https://github.com/bem/bem-xjst/releases/tag/v4.3.3');
        }
      });
    }

    return ret;
  });

  // mods для elem (вместо elemMods)
  block('*').def()(function() {
    var ret = applyNext();

    var ctx = this.ctx;
    if (ctx.mods && ctx.elem && !ctx.elemMods) {
        console.warn(
          '\nWARNING: mods for elem in BEMJSON:',
          ctx
        );
        console.warn('Notice what bem-xjst behaviour changed: https://github.com/bem/bem-xjst/releases/tag/v5.0.0');
    }

    return ret;
  });

  // присвоения в ctx.mods
  // block('*').def()(function() {
  //   var ret = applyNext();

  //   var ctx = this.ctx;

  //   if (this.block === 'mods-test')
  //     ctx.mods.one = 2;

  //   return ret;
  // });

  block('*').def()(function() {
    var ret;

    var ctx = this.ctx;
    var mods = ctx.mods;
    if (mods) {
        var store = Object.keys(mods).map(function(key) {
          return {
            key: key,
            val: mods[key]
          };
        });

      ret = applyNext();

      store.forEach(function(mod) {
        var key = mod.key;
        if (mods[key] !== mod.val) {
          console.warn(
            '\nWARNING: looks like someone changed ctx.mods in BEMJSON:',
            ctx,
            '\nold value of ctx.mod.' + mod.key + ' was ' + mod.val,
            '\nNotice that bem-xjst recommend to change this.mods instead of this.ctx.mods in templates'
          );
        }
      });
    } else {
      ret = applyNext();
    }

    return ret;
  });
});

// Tests
templates.apply([
  // basic
  { block: 'a' },

  // boolean attributes
  { block: 'b', attrs: { one: true, two: 'true' } },

  // mods for elem
  { block: 'c', elem: 'e', mods: { test: 'opa' } },

  // присвоения в ctx.mods
  { block: 'mods-test', mods: { one: '1', two: '2' } }
]);
// Result: <div class="b">yay</div>