JSON string as template

[jimfum]

Hi,

I'm trying to use the following JSON string as a template

var template = @"{
  ""sentence1"" : ""Your custom text is: {{{customText}}}"",
  ...
}";
var f = handlebars.Compile(template);
f(new { customText = "quoted text follows - ""foo""" });

The render becomes an invalid JSON because of the un-escaped double quotes (as also highlighted below):

{
  "sentence1" : "Your custom text is: quoted text follows - "foo"",
  ...
}";

Is there a way to solve it? Like provide custom text processor. I've already checked ITextEncoder but that's only used together with {{ and not {{{ as sort of expected. I need to execute my JSON encoding for every inserted text.

Thanks

[oformaniuk]

Hi @jimfum
You may use HandlebarsTemplate<TextWriter, object, object> delegate to pass custom TextWriter and do text processing as you need.

[oformaniuk]

@jimfum , the thing is that I cannot get what manipulations with the json and dictionaries you're doing. Seeing it in the form of failing test helps to understand it better.
I understood that you're trying to optimize but I cannot understand hot template from json becomes part of the main template without rendering it first.

[rexm]

I don’t understand why these key-values that also contain Handlebars syntax aren’t helpers.

[jimfum]

@zjklee, exactly right, the template from json is rendered first, deserialized and used as an input to the main template. I'll add a test demonstrating the json manipulation. And to emphasize, I'm not pointing to any bug, it behaves as it should just not giving me what is needed.

@rexm, we use custom helpers quite a bit but don't see how they'd help here. The only idea coming to mind would be a helper, that does handlebars compile & render on the text it receives (the values from JSON) . That would generate a lot of memory allocation and GC as there're a lot of those to process. If your idea is different, could you pls demonstrate on the example above?

Thanks both of you.

[oformaniuk]

@jimfum,

I'll add a test demonstrating the json manipulation

Code (test in our case) is the best explanation of what you want to achieve. Try to expose what you want and what is failing as close to real scenario as possible but keeping only important details.

And to emphasize, I'm not pointing to any bug, it behaves as it should just not giving me what is needed.

I understand, I'm just curious to make it work and do it in optimal way at the same time.

[jimfum]

I'm not sure myself now I can clearly demonstrate the challenges. Please find a couple of tests below. The reason for all of this is pretty much #493.

[Fact]
public void Test1()
{
	// {{{ here because we know the value from JSON contains HTML
	const string Template = @"<p>{{{dataFromJson.sayHello}}}</p><p>{{generatedOn}}</p>";
	// {{ would make more sense here but it's user's choice. neither option
	// should end up with exception
	const string Json1 = @"{
		""sayHello"": ""Hi <b>{{{customerName}}}</b>""
		// + many others
	}";

	var handlebars = Handlebars.Create();
	var renderMain = handlebars.Compile(Template);
	var renderJson = handlebars.Compile(Json1);

	dynamic data = new ExpandoObject();
	// the value isn't JSON escaped while we know it's going to be placed
	// into JSON string. issues expected.
	data.customerName = @"John "" Joshua";

	string renderedJson = renderJson(data);
	var jsonDeserialized = JsonConvert.DeserializeObject<Dictionary<string, string>>(renderedJson);

	data.generatedOn = "2022-01-01";
	data.dataFromJson = jsonDeserialized;

	var render = renderMain(data);

	// fails:
	// Newtonsoft.Json.JsonReaderException
	// After parsing a value an unexpected character was encountered:
	// J.Path 'sayHello', line 2, position 42.
	// EXPECTED as we produced invalid JSON string by injecting an unescaped substring (customerName)
	Assert.Equal(@"<p>Hi <b>John "" Joshua</b></p><p>2022-01-01</p>", render);
}

[Fact]
public void Test2()
{
	const string Template = @"<p>{{{dataFromJson.sayHello}}}</p><p>{{generatedOn}}</p>";
	// decided to use {{. makes more sense.
	const string Json1 = @"{
		""sayHello"": ""Hi <b>{{customerName}}</b>""
		// + many others
	}";

	var handlebars = Handlebars.Create();
	var renderMain = handlebars.Compile(Template);
	var renderJson = handlebars.Compile(Json1);

	dynamic data = new ExpandoObject();
	// JSON escaped ". Logical as we know we're injecting it into valid JSON string.
	data.customerName = @"John \"" Joshua";

	string renderedJson = renderJson(data);
	var jsonDeserialized = JsonConvert.DeserializeObject<Dictionary<string, string>>(renderedJson);

	data.generatedOn = "2022-01-01";
	data.dataFromJson = jsonDeserialized;

	var render = renderMain(data);

	// Newtonsoft.Json.JsonReaderException
	// Bad JSON escape sequence: \&.Path 'sayHello', line 2, position 42.
	// REASON: we JSON escaped customerName and then HTML escaped because of {{.
	// The right order would be HTML and then JSON espacing.
	Assert.Equal(@"<p>Hi <b>John &quot; Joshua</b></p><p>2022-01-01</p>", render);
}