autoescape.js

function AutoEscapeExtension(_env) {
    this.tags = ['autoescape'];

    this.parse = function(parser, nodes, lexer) {
        // get the tag token
        var tok = parser.nextToken();

        // parse the args and move after the block end. passing true
        // as the second arg is required if there are no parentheses
        var args = parser.parseSignature(null, true);
        parser.advanceAfterBlockEnd(tok.value);

        // parse the body and possibly the error block, which is optional
        var body = parser.parseUntilBlocks('endautoescape');

        parser.advanceAfterBlockEnd();

        // See above for notes about CallExtension
        return new nodes.CallExtension(this, 'run', args, [body]);
    };

    this.run = function(context, mode, body) {
        var ret, before = _env.autoesc;
        _env.autoesc = !!mode;
        ret = new nunjucks.runtime.SafeString(body());
        _env.autoesc = before;
        return ret;
    };
}

env.addExtension('AutoEscapeExtension', new AutoEscapeExtension(env));

test.html

{% autoescape false %}
This is a {{ test }}
{% endautoescape %}