Hey @valyala! Thanks for the great lib!
We have a lot of code, for url macros substitutioning with strings.Replacer. When we realised, that it was using too much memory, we chose your lib to optimize the performance.

But the main problem is that we are using different replacers not once on a single template string, but many times.
Example

a := "{a}{b}"
r := strings.Replace(a, "{a}", "1") // r == 1{b}
...(other part of code)...
r = strings.Replace(r, "{b}", "2") // r == 12

with replacers all is fine, but your engine skips the unknown values by default.

a := "{a}{b}"
r := fasttemplate.ExecuteString(a, "{", "}", map[string]intreface{}{"a": "1"}) // r == 1
...(other part of code)...
r = fasttemplate.ExecuteString(r, "{", "}", map[string]intreface{}{"b": "2"}) // r == 1

We made a wrapper for your lib, that fixes that. It actually just changes a little the stdTagFunc.

What do you think of making this the default behaviour to make the engine more compatible with strings.Replacer? PR will be made on having your approve

I only see the example of rendering html code, there is no example of rendering html files?

template := "http://{{host}}/?q={{query}}&foo={{bar}}"
	t := fasttemplate.New(template, "{{", "}}")
	s1 := t.ExecuteString(map[string]interface{}{
		"host":  "google.com",
		"query": url.QueryEscape("hello=world"),
		"bar":   22,
})

In my case, there are always int/bool/float type to template.

Error:

panic: tag="bar" contains unexpected value type=22. Expected []byte, string or TagFunc

Is it possible to match a nested map object's key?
For example I having a variable shown below:

input := map[string]interface{}{
  "user": map[string]interface{}{
	  "name": "James",
	  "age":  "20",
  },
}

Example template

"Hi, my name is {{user.name}}, I'm {{user.age}} years old."

How do I get the {{user.name}} as the tags for template when calling ExecuteStringStd() ? I tried with {{user.name}} but it doesn't work.

Hey, thanks for this awesome library!

At present, there is no way to include a startTag in the template string without the engine picking up on it as a tag:

I'd like to use this with some user defined templates, where there might well be a use case for them having whatever character I choose for the startTag in their template string proper. Using backslashes to escape would be the obvious option, but there's currently no functionality for anything of this sort in the library as far as I can see - so consider this a feature request :)

Cheers!

Hi.
I have implemented fasttemplate and have a question about pass ExecuteString value to http.ResponseWriter. How can it be done?

fasttemplate is used by echo, a web framework, for its logger.
I currently use echo on Google App Engine, and it throws the following error :

2017/01/16 16:08:42 go-app-builder: Failed parsing input: parser: bad import "unsafe" in github.com/valyala/fasttemplate/template.go from GOPATH

As far as I understand, fasttemplate now relies heavily on unsafe for performance optimizations.
How could we workaround this so that fasttemplate and echo stay compatible with GAE ?

He. Why do you have the minimum required version Go 1.12?

In my application. all my template subsitutions are strings. I want to improve the templating engine more, such that it won't assert the interface or somehow, and directly stream the string as is.

since all my database read values are in strings. I want to use map[string]string insead if it would increase the subsitution effieciency more.

How is this approach possible ?

thank you in advance

I found that if ExecuteFunc returns an error, ExecuteFuncString will use panic. I think returning an error is more reasonable.
See https://github.com/valyala/fasttemplate/blob/master/template.go#L91

Why do you use a worker pool for bytes.Buffers that are template-specific (vs. a global pool)? Is it for getting similar sized buffers each time, or is there another reason?

Trying to deploy my code based on Echo Framework, and getting GAE error:

ERROR: (gcloud.app.deploy) Error Response: [9] Deployment contains files that cannot be compiled: Compile failed:
/work_dir/github.com/valyala/fasttemplate/template.go:12: can't find import: "github.com/valyala/bytebufferpool"
2017/12/22 23:38:09 go-app-builder: build timing: 15×compile (4.677s total), 0×link (0s total)
2017/12/22 23:38:09 go-app-builder: failed running compile: exit status 2

As far as I can see, GAE from Go 1.9.1 (I believe) stop reading subpackage vendors folder. When I delete /vendors folder in fasttemplate, build going through without issues.

We are using this lib in our online system, and in a load test, we found that if the Template generated is not reused(eg.by sync.Map), there will be strong contention when the load is high:

goroutine profile: total 18910
18903 @ 0x102f20b 0x102f2b3 0x103fa4c 0x103f77d 0x10714df 0x1071d8f 0x1071d26 0x1071a5f 0x12feeb8 0x13005f0 0x13007c3 0x130107b 0x105c931
#	0x103f77c	sync.runtime_SemacquireMutex+0x3c								/usr/local/go/src/runtime/sema.go:71
#	0x10714de	sync.(*Mutex).Lock+0xfe										/usr/local/go/src/sync/mutex.go:134
#	0x1071d8e	sync.(*Pool).pinSlow+0x3e									/usr/local/go/src/sync/pool.go:198
#	0x1071d25	sync.(*Pool).pin+0x55										/usr/local/go/src/sync/pool.go:191
#	0x1071a5e	sync.(*Pool).Get+0x2e										/usr/local/go/src/sync/pool.go:128
#	0x12feeb7	github.com/valyala/fasttemplate/vendor/github.com/valyala/bytebufferpool.(*Pool).Get+0x37	/Users/xargin/go/src/github.com/valyala/fasttemplate/vendor/github.com/valyala/bytebufferpool/pool.go:49
#	0x13005ef	github.com/valyala/fasttemplate.(*Template).ExecuteFuncString+0x3f				/Users/xargin/go/src/github.com/valyala/fasttemplate/template.go:278
#	0x13007c2	github.com/valyala/fasttemplate.(*Template).ExecuteString+0x52					/Users/xargin/go/src/github.com/valyala/fasttemplate/template.go:299
#	0x130107a	main.loop.func1+0x3a										/Users/xargin/test/go/http/httptest.go:22

and after we use sync.Map to store the generated template objects, the piled goroutines disappear.

Maybe you need to warn users about this?