Azure Application Gateway - Url can't be set without causing Query String to be empty

[adrianperez84]

When writing a rewrite rule where the intent is to only update the path without rewriting the query string, Terraform will set an empty string on the query string. This is a significant problem, as it causes query strings to be lost when using rewrite rules. I'm using the latest version 2.82.0.

rewrite_rule_set { name = "rwruleset" rewrite_rule {

            name                   = "rwrule1"
            rule_sequence          = 1

         
            condition {
               
                variable           = "var_uri_path"
                pattern            = "/checkout/(.+)"
             
            }
            url {
                path               = "/{var_uri_path_1}" 
                # query_string         The query string should not be set by Terraform as empty string. 
               
            }
    } 
}

This was originally discovered here: https://github.com/hashicorp/terraform-provider-azurerm/pull/10950 . You can notice that this snippet of code will incorrectly assume that both Path and Query String needs to be rewritten.

rewrite_rule_set {
    name = "test-rewrite-ruleset"

    rewrite_rule {
      name          = "test-rewrite-rule"
      rule_sequence = 1

      condition {
        variable = "var_uri_path"
        pattern  = ".*article/(.*)/(.*)"
      }

      url {
        path         = "/article.aspx"
      }
    }
  }

Having inspected the state file, I think I see the problem. When no value is provided the state file shows that there is a value of "" (an empty string), which probably means the query_string is essentially being replaced by the rewrite rule.

I'm not entirely sure why this is the case, but I'll do some investigation as to why empty strings are going through when no value is provided.

Originally posted by @dhensby in https://github.com/hashicorp/terraform-provider-azurerm/issues/10950#issuecomment-822334088

[dhensby]

Duplicate of #11563

[aristosvo]

@adrianperez84 @dhensby I just submitted a PR which can circumvents the limitations we currently have by using a components option, similar to the UI:

...
   rewrite_rule_set {
     name = "${local.rewrite_rule_set_name}_1"
     rewrite_rule {
       name          = "${local.rewrite_rule_name}_1"
       rule_sequence = 1
       condition {
         variable = "var_uri_path"
         pattern  = ".*article/(.*)/(.*)"
       }
       url {
         path       = "/article.aspx"
         components = "path_only"
       }
     }
     rewrite_rule {
       name          = "${local.rewrite_rule_name}_2"
       rule_sequence = 2
       condition {
         variable = "var_uri_path"
         pattern  = ".*article2/(.*)/(.*)"
       }
       url {
         query_string = "id={var_uri_path_1}&title={var_uri_path_2}"
         components   = "query_string_only"
       }
     }
   }
...

Happy to hear your thoughts about it!

[github-actions[bot]]

This functionality has been released in v3.4.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions[bot]]

This functionality has been released in v3.19.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions[bot]]

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