templateRewriting.js

ko.templateRewriting = (function () {
    var memoizeDataBindingAttributeSyntaxRegex = /(<([a-z]+\d*)(?:\s+(?!data-bind\s*=\s*)[a-z0-9\-]+(?:=(?:\"[^\"]*\"|\'[^\']*\'|[^>]*))?)*\s+)data-bind\s*=\s*(["'])([\s\S]*?)\3/gi;
    var memoizeVirtualContainerBindingSyntaxRegex = /<!--\s*ko\b\s*([\s\S]*?)\s*-->/g;

    function validateDataBindValuesForRewriting(keyValueArray) {
        var allValidators = ko.expressionRewriting.bindingRewriteValidators;
        for (var i = 0; i < keyValueArray.length; i++) {
            var key = keyValueArray[i]['key'];
            if (allValidators.hasOwnProperty(key)) {
                var validator = allValidators[key];

                if (typeof validator === "function") {
                    var possibleErrorMessage = validator(keyValueArray[i]['value']);
                    if (possibleErrorMessage)
                        throw new Error(possibleErrorMessage);
                } else if (!validator) {
                    throw new Error("This template engine does not support the '" + key + "' binding within its templates");
                }
            }
        }
    }

    function constructMemoizedTagReplacement(dataBindAttributeValue, tagToRetain, nodeName, templateEngine) {
        var dataBindKeyValueArray = ko.expressionRewriting.parseObjectLiteral(dataBindAttributeValue);
        validateDataBindValuesForRewriting(dataBindKeyValueArray);
        var rewrittenDataBindAttributeValue = ko.expressionRewriting.preProcessBindings(dataBindKeyValueArray, {'valueAccessors':true});

        // For no obvious reason, Opera fails to evaluate rewrittenDataBindAttributeValue unless it's wrapped in an additional
        // anonymous function, even though Opera's built-in debugger can evaluate it anyway. No other browser requires this
        // extra indirection.
        var applyBindingsToNextSiblingScript =
            "ko.__tr_ambtns(function($context,$element){return(function(){return{ " + rewrittenDataBindAttributeValue + " } })()},'" + nodeName.toLowerCase() + "')";
        return templateEngine['createJavaScriptEvaluatorBlock'](applyBindingsToNextSiblingScript) + tagToRetain;
    }

    return {
        ensureTemplateIsRewritten: function (template, templateEngine, templateDocument) {
            if (!templateEngine['isTemplateRewritten'](template, templateDocument))
                templateEngine['rewriteTemplate'](template, function (htmlString) {
                    return ko.templateRewriting.memoizeBindingAttributeSyntax(htmlString, templateEngine);
                }, templateDocument);
        },

        memoizeBindingAttributeSyntax: function (htmlString, templateEngine) {
            return htmlString.replace(memoizeDataBindingAttributeSyntaxRegex, function () {
                return constructMemoizedTagReplacement(/* dataBindAttributeValue: */ arguments[4], /* tagToRetain: */ arguments[1], /* nodeName: */ arguments[2], templateEngine);
            }).replace(memoizeVirtualContainerBindingSyntaxRegex, function() {
                return constructMemoizedTagReplacement(/* dataBindAttributeValue: */ arguments[1], /* tagToRetain: */ "<!-- ko -->", /* nodeName: */ "#comment", templateEngine);
            });
        },

        applyMemoizedBindingsToNextSibling: function (bindings, nodeName) {
            return ko.memoization.memoize(function (domNode, bindingContext) {
                var nodeToBind = domNode.nextSibling;
                if (nodeToBind && nodeToBind.nodeName.toLowerCase() === nodeName) {
                    ko.applyBindingAccessorsToNode(nodeToBind, bindings, bindingContext);
                }
            });
        }
    }
})();


// Exported only because it has to be referenced by string lookup from within rewritten template
ko.exportSymbol('__tr_ambtns', ko.templateRewriting.applyMemoizedBindingsToNextSibling);