xpress

import "github.com/nonsocode/xpress"

xpress is a simple and fast template engine for Go.

Basic Usage

package main

import (
	"fmt"
	"github.com/nonsocode/xpress/pkg/parser"
)

func main() {
	// create a parser
	p := parser.NewParser("Hello, @{{ name }}!")

	// parse the template
	ast := p.Parse()

	// create an evaluator
	e := parser.NewInterpreter()

	// set members
	e.SetMembers(map[string]interface{}{
		"name": "John",
	})

	// evaluate the template
	res, err := e.Evaluate(ast)
	if err != nil {
		panic(err)
	}
	fmt.Println(res)	// Hello, John!
}

You can reuse the evaluator for multiple templates:

func main() {
	// create an evaluator with members
	e := parser.NewInterpreter()
	e.SetMembers(map[string]interface{}{
		"name": "John",
		"concat": func(a, b string) string {
			return a + b
		},
	})

	// create an AST
	ast := parser.NewParser("Hello, @{{ name }}!").Parse()

	// evaluate the template
	res, err := e.Evaluate(ast)
	if err != nil {
		panic(err)
	}
	fmt.Println(res)	// Hello, John!

	// create another AST
	p = parser.NewParser("Hello, @{{ concat(name, ' Doe') }}!").Parse()

	// evaluate the template
	res, err = e.Evaluate(ast)
	if err != nil {
		panic(err)
	}
	fmt.Println(res)	// Hello, John Doe!
}

Template Syntax

The template syntax is loosely inspired by javascript syntax. When a template is evaluated, If the template begins and ends exactly with the template delimiters, the template will be return the exact result of the operation regardless of the type of the result. Otherwise, the result will be converted to a string.

// "@{{ 1 + 2 }}" will return number `3`
// "@{{ 1 + 2 }} "  will return string `3 `.

Members

Members are variables and functions that can be accessed from the template. When defining functions, You can optionally define the first argument as context.Context. A context will be passed to the function when it is called. Functions must return either 1 or 2 values. If the function returns 1 value, it will be used as the result of the function call. If the function returns 2 values, the first value will be used as the result of the function call and the second value will be used as an error. If the error is not nil, the evaluation will be aborted and the error will be returned.

Benchmarks

goos: linux
goarch: amd64
pkg: github.com/nonsocode/xpress/pkg/parser
cpu: AMD EPYC 7763 64-Core Processor
BenchmarkComplexParser-2          126980              9935 ns/op            7648 B/op         70 allocs/op
BenchmarkSimpleParser-2           630464              2714 ns/op            1696 B/op         18 allocs/op
BenchmarkEvaluator-2               34920             36895 ns/op            4440 B/op         97 allocs/op

Index

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