Question

Regex with replace in Golang

{% macro products_list(products) %}
{% for product in products %}
productsList
{% endfor %}
{% endmacro %}

I could not replace “products” without replace another words like “products_list” and Golang has no a func like re.ReplaceAllStringSubmatch to do replace with submatch (there’s just FindAllStringSubmatch). I’ve used re.ReplaceAllString to replace “products” with .

{% macro ._list(.) %}
{% for product in . %}
.List
{% endfor %}
{% endmacro %}
But I need this result:

{% macro products_list (.) %}
{% for product in . %}
productsList
{% endfor %}
{% endmacro %}
regexgo
 

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KFSys
Site Moderator
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May 24, 2023

Heya,

The problem you’re trying to solve involves replacing only the “products” string within the parentheses, while leaving other instances of “products” untouched.

Here’s an example that might work for you. In this example, a regular expression with a lookahead and lookbehind assertion is used to target only the specific “products” string that you want to replace:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    template := `{% macro products_list(products) %} {% for product in products %} productsList {% endfor %} {% endmacro %}`
    re := regexp.MustCompile(`(?<=products_list\()products(?=\))`)
    result := re.ReplaceAllString(template, ".")
    fmt.Println(result)
}

In the regular expression (?<=products_list\()products(?=\)):

  • (?<=products_list\() is a positive lookbehind that matches “products_list(” before “products”.
  • products is the target string to replace.
  • (?=\)) is a positive lookahead that matches “)” after “products”.

The ReplaceAllString method then replaces only the “products” strings that meet these conditions with “.”.

Please remember that Go’s regexp package does not support every feature of regular expressions, and the use of lookaheads and lookbehinds is one such unsupported feature (as of my knowledge cutoff in September 2021). However, this example should help you understand the logic required to solve your problem.

If you need to use advanced regular expression features in Go, you may want to consider third-party libraries that offer this functionality, such as github.com/dlclark/regexp2, which is a Go library that supports more features than the standard regexp package.

Finally, keep in mind that using regular expressions to parse or modify code or markup languages can be complex and error-prone due to the inherent complexity of these languages’ syntax. If you’re dealing with complex templates or if you need more flexible replacements, you might want to consider using a proper parser for the Jinja2 language.

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