Templating support

[patriksvensson]

Would be nice with some kind of templating support to easily replace tokens in a template to produce an new file. For example; setting the Version property in a psd1 template to produce a new file.

With this in place, other templating stuff in Cake such as nuspec transformations could just be a wrapper around this functionality.

[devlead]

Perhaps just add T4 support using sdk TextTransform.exe, that could also enable recompiling .tt files in cake build scripts.

T4 is well tested and basically just "asp" for codegen.

[patriksvensson]

T4 support would be very nice indeed, but I was thinking about something really lightweight that doesn't require TextTransform.exe.

[rofr]

new Template("How about {word} like this?").Render(new Dictionary<string,string>({{"word", "something"}}));

[patriksvensson]

Yes, something like that. Just to make it simple to do very simple transformastions such as setting a version number in a file or something similar.

However, I think T4 support would be very nice as well :)

[rofr]

Here's something I use in production :) https://gist.github.com/rofr/ab9b6868f81c09b8aa79
updated: removed the xml hacks

[devlead]

I've written a couple DSLs with help of RegEx;) you can indeed with fairly simple measures solve complex scenarios. As long as you keep a limited scope it can be very useful. But can also be a rabbit hole ;)
That said gotten very performant code running on busy web sites using RegEx as correctly done only matches are processed.
You could have special template "tags" like <%command:parameters%> I.e <%now:format="yyyy-MM-dd" utc="true"%>

Personally I wouldn't mind the TextTransform.exe dependency, passing an assembly and/or parameters (-a !!param!value) could enable a simple view model to apply the template on.

You can also host the T4 engine but wouldn't recommend that.

[orjan]

What about just adding mustasche?

Sent from my iPhone

On 29 nov 2014, at 00:19, Patrik Svensson [email protected] wrote:

Yes, something like that. Just to make it simple to do very simple transformastions such as setting a version number in a file or something similar.

However, I think T4 support would be very nice as well :)

—
Reply to this email directly or view it on GitHub.

[patriksvensson]

I've been doing some investigation and come to the conclusion that T4-templating will not be used for this since it has a dependency on Microsoft.VisualStudio.TextTemplating which isn't very portable. For this a very simple solution is good enough, but T4-support could be implemented as a feature of it's own.

I've prototyped a simple API that I will try to implement and try out.

TransformText("{greeting} {word}!")
   .WithToken("greeting", "Hello")
   .WithToken("word", "World")
   .Save("./transformed.txt");

TransformText("{greeting} {word}!")
   .WithToken("greeting", "Hello")
   .WithToken("word", "World")
   .ToString();

TransformTextFile("./template.txt")
   .WithToken("greeting", "Hello")
   .WithToken("word", "World")
   .Save("./transformed.txt");

Any thoughts or suggestions?

[devlead]

Looks nice, TransformText could take an optional IDictionary great if same parameters is used for many transformations, easy to serialize, could also be used as seed for the WithToken
WithToken could be <string, object> to support any value.

[patriksvensson]

Yes, that's a great idea. Actually, both TransformText and TransformTextFile could have an optional parameter with an IDictionary<string, object>.

var tokens = new Dictionary<string, object>
{
   { "name", "Patrik" }
   { "age", 12 },
}

TransformText("{greeting} {name}!", tokens)
   .WithToken("greeting", "Hello")
   .Save("./transformed.txt");

Got a better name for WithToken btw?

[devlead]

Perhaps use more rare token identifier i.e. <%tag%> to easier support code generation, something like below supporting both Cake reserved keywords and supplied dictionary:

        private static readonly Regex TokenRegex = new Regex(
            "<%(?![#$])(([^%]*)%)*?>",
            RegexOptions.Singleline | RegexOptions.Compiled
            );

        internal static string RenderedTemplate(
            string template,
            IDictionary<string, object> tokens,
            IFormatProvider culture = null
            )
        {
            var renderedTemplate = TokenRegex.Replace(
                template,
                match => tokens.ReplaceToken(
                    match,
                    culture ?? CultureInfo.InvariantCulture
                    )
                );
            return renderedTemplate;
        }

        private static string ReplaceToken(
            this IDictionary<string, object> tokens,
            Match match,
            IFormatProvider culture = null
            )
        {
            var token = match.Groups
                .OfType<Group>()
                .Select(group => @group.Value)
                .LastOrDefault()
                        ?? match.Value.Trim('<', '%', '>');

            var key = string.Concat(
                token
                    .Select(CultureInfo.InvariantCulture.TextInfo.ToLower)
                    .TakeWhile(
                        c => c != ':'
                    )
                );

            var format = string.Format(
                "{{0{0}}}",
                string.Concat(
                    token
                        .SkipWhile(
                            c => c != ':'
                        )
                    )
                );

            object value;
            switch (key)
            {
                case "now":
                    value = DateTime.Now;
                    break;
                case "utcnow":
                    value = DateTime.UtcNow;
                    break;
                default:
                    value = tokens.TryGetValue(key, out value)
                        ? string.Format(
                            culture ?? CultureInfo.InvariantCulture,
                            format,
                            value
                            )
                        : match.Value;
                    break;
            }
            return string.Format(
                culture,
                format,
                value
                );
        }

Could be used something like this

            var tokens = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase)
            {
                {"greeting", "Hello"},
                {"firstname", "John"},
                {"lastname", "Doe"},
                {"age", 25},
                {"offer", 125.3555m}
            };
            var renderedTemplate = RenderedTemplate(
                @"<%greeting%> <%firstname%> <%lastname%>,
you are <%age%> years old.
Special price for you is <%offer:c2%>
Template generated <%now:yyyy-MM-dd HH:mm:ss%> (Utc: <%utcnow:yyyy-MM-dd HH:mm:ss%>)
",
                tokens,
                new CultureInfo("sv-SE")
                );
            Information(renderedTemplate);

Outputing something like:

Hello John Doe,
you are 25 years old.
Special price for you is 125,36 kr
Template generated 2014-12-16 09:58:01 (Utc: 2014-12-16 08:58:01)

one could get a group for format to... but above should illustrate what I mean;)

[patriksvensson]

I like the idea, but I would want to keep this kind of templating support very, very simple. Of course, nothing prevents us from expanding it by building on top of it when it's ready, but for the time being I think there is a clear benefit of keeping it as simple as possible until we know what we want.

Maybe a T4 tool wrapper would be a better approach?

[devlead]

Isn't above very simple? Just a regex, switch and a dictionary?;) More advanced features could indeed be added later.

Yeah think T4 should be it's own tool.

[patriksvensson]

The code is very simple and readable, but the functionality itself isn't. By providing "expressions" like now and utcnow it would be tempting to also let the user define his/her own expressions that will or will not support formats. In this case it might be better to provide a full fledged templating engine such as mustache as @orjan was suggesting or T4.

Please note that I'm not against your suggestion. I just think it feels better to keep the templating functionality to a minimum until we know what kind of functionality we want. I don't want to be a dictator here so of course I want a discussion about this 😄

I don't know. Could we limit the scope of this? Include hard coded expression? Include custom expressions? What do you think?

[devlead]

well remove the switch then;)

[RichiCoder1]

I'd throw in my two cents and say that I'd be a fan of including https://github.com/jehugaleahsa/mustache-sharp. I would say, though, that anything beyond string.Format() is going to be complex by it's nature very quickly and it'd be better to bring in a full fledged engine from the start.