Callback with x-www-form-urlencoded expression

[thomascombe]

Context

My app specification has a callback using expressions from x-www-form-urlencoded ({$request.body#/url}).
The URL parameter is not decoded from FORM Url-Encode (it works when using JSON)

Current Behavior

Callback not executed:

[15:34:01] ›     [CALLBACK] ℹ  info      actions: > Executing "post" callback to ?token=...
[15:34:01] ›     [CALLBACK] ✖  error     actions: Request failed: Only absolute URLs are supported

Expected Behavior

The callback should execute the same way as it does for a JSON request.

[4:23:48 PM] ›     [CALLBACK] ℹ  info      actions: > Executing "post" callback to http://localhost:4011/notify?token=ssecurre...
[4:23:48 PM] ›     [CALLBACK] ✖  error     actions: Request failed: request to http://localhost:4011/notify?token=ssecurre failed, reason: 

(SSL error because of localhost env)

Possible Workaround/Solution

If I dump request, I can find custom path around my JSON:

{
  method: 'post',
  url: { path: '/invoices/123/subscribe', baseUrl: undefined, query: {} },
  headers: {
    host: '127.0.0.1:4010',
    'user-agent': 'curl/8.7.1',
    accept: '*/*',
    'content-type': 'application/x-www-form-urlencoded',
    'content-length': '57'
  },
  body: {
    _tag: 'Right',
    right: { url: 'http://localhost:4011/notify', token: 'ssecurre' }
  }
}

(packages/http/src/mocker/callback/callbacks.ts:runCallback)

_tag and right are added by packages/http/src/validator/validators/body.ts:deserializeFormBody)

Steps to Reproduce

Use callback example and change application/json validation to x-www-form-urlencoded.

{
  "openapi": "3.0.0",
  "paths": {
    "/invoices/{id}/subscribe": {
      "parameters": [
        {
          "name": "id",
          "in": "path",
          "required": true,
          "description": "The id of the invoice about which you want to receive notifications",
          "schema": {
            "$ref": "#/components/schemas/invoiceId"
          }
        }
      ],
      "post": {
        "summary": "Subscription to events about given invoice",
        "requestBody": {
          "required": true,
          "content": {
            "application/x-www-form-urlencoded": {
              "schema": {
                "type": "object",
                "properties": {
                  "url": {
                    "type": "string",
                    "format": "uri"
                  },
                  "token": {
                    "type": "string"
                  }
                },
                "required": [
                  "url",
                  "token"
                ]
              }
            }
          }
        },
        "responses": {
          "202": {
            "description": "Successfully subscribed to events about given invoice",
            "content": {
              "text/plain": {
                "examples": {
                  "ok": {
                    "value": "ok"
                  }
                }
              }
            }
          }
        },
        "callbacks": {
          "actions": {
            "{$request.body#/url}?token={$request.body#/token}": {
              "post": {
                "summary": "Receive notification about certain invoice",
                "requestBody": {
                  "required": true,
                  "content": {
                    "application/json": {
                      "schema": {
                        "$ref": "#/components/schemas/notification"
                      }
                    }
                  }
                },
                "responses": {
                  "200": {
                    "description": "Notification successfully processed",
                    "content": {
                      "text/plain": {
                        "examples": {
                          "ok": {
                            "value": "ok"
                          }
                        }
                      }
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "schemas": {
      "invoiceId": {
        "type": "integer",
        "format": "int64"
      },
      "notification": {
        "type": "object",
        "properties": {
          "invoiceId": {
            "$ref": "#/components/schemas/invoiceId"
          },
          "action": {
            "type": "string",
            "enum": [
              "paid",
              "expired",
              "failure"
            ]
          }
        },
        "required": [
          "invoiceId",
          "action"
        ]
      }
    }
  }
}

Run prism:

prism mock mock.json -v=trace

Launch curl:

curl -v -X POST \
  -H "Content-Type: application/x-www-form-urlencoded" \
  --data-urlencode "url=http://localhost:4011/notify" \
  --data-urlencode "token=ssecurre" \
  http://127.0.0.1:4010/invoices/123/subscribe

Environment

• Version used: 5.14.2
• Environment name and version: NodeJS v25.2.1
• Operating System and version (desktop or mobile): MacOS

[rnagulapalle]

Context

My app specification has a callback using expressions from x-www-form-urlencoded ({$request.body#/url}). The URL parameter is not decoded from FORM Url-Encode (it works when using JSON)

Current Behavior

Callback not executed:

[15:34:01] ›     [CALLBACK] ℹ  info      actions: > Executing "post" callback to ?token=...
[15:34:01] ›     [CALLBACK] ✖  error     actions: Request failed: Only absolute URLs are supported

Expected Behavior

The callback should execute the same way as it does for a JSON request.

[4:23:48 PM] ›     [CALLBACK] ℹ  info      actions: > Executing "post" callback to http://localhost:4011/notify?token=ssecurre...
[4:23:48 PM] ›     [CALLBACK] ✖  error     actions: Request failed: request to http://localhost:4011/notify?token=ssecurre failed, reason: 

(SSL error because of localhost env)

Possible Workaround/Solution

If I dump request, I can find custom path around my JSON:

{
method: 'post',
url: { path: '/invoices/123/subscribe', baseUrl: undefined, query: {} },
headers: {
host: '127.0.0.1:4010',
'user-agent': 'curl/8.7.1',
accept: '/',
'content-type': 'application/x-www-form-urlencoded',
'content-length': '57'
},
body: {
_tag: 'Right',
right: { url: 'http://localhost:4011/notify', token: 'ssecurre' }
}
}
(packages/http/src/mocker/callback/callbacks.ts:runCallback)

_tag and right are added by packages/http/src/validator/validators/body.ts:deserializeFormBody)

Steps to Reproduce

Use callback example and change application/json validation to x-www-form-urlencoded.

{
"openapi": "3.0.0",
"paths": {
"/invoices/{id}/subscribe": {
"parameters": [
{
"name": "id",
"in": "path",
"required": true,
"description": "The id of the invoice about which you want to receive notifications",
"schema": {
"$ref": "#/components/schemas/invoiceId"
}
}
],
"post": {
"summary": "Subscription to events about given invoice",
"requestBody": {
"required": true,
"content": {
"application/x-www-form-urlencoded": {
"schema": {
"type": "object",
"properties": {
"url": {
"type": "string",
"format": "uri"
},
"token": {
"type": "string"
}
},
"required": [
"url",
"token"
]
}
}
}
},
"responses": {
"202": {
"description": "Successfully subscribed to events about given invoice",
"content": {
"text/plain": {
"examples": {
"ok": {
"value": "ok"
}
}
}
}
}
},
"callbacks": {
"actions": {
"{$request.body#/url}?token={$request.body#/token}": {
"post": {
"summary": "Receive notification about certain invoice",
"requestBody": {
"required": true,
"content": {
"application/json": {
"schema": {
"$ref": "#/components/schemas/notification"
}
}
}
},
"responses": {
"200": {
"description": "Notification successfully processed",
"content": {
"text/plain": {
"examples": {
"ok": {
"value": "ok"
}
}
}
}
}
}
}
}
}
}
}
}
},
"components": {
"schemas": {
"invoiceId": {
"type": "integer",
"format": "int64"
},
"notification": {
"type": "object",
"properties": {
"invoiceId": {
"$ref": "#/components/schemas/invoiceId"
},
"action": {
"type": "string",
"enum": [
"paid",
"expired",
"failure"
]
}
},
"required": [
"invoiceId",
"action"
]
}
}
}
}
Run prism:

prism mock mock.json -v=trace
Launch curl:

curl -v -X POST
-H "Content-Type: application/x-www-form-urlencoded"
--data-urlencode "url=http://localhost:4011/notify"
--data-urlencode "token=ssecurre"
http://127.0.0.1:4010/invoices/123/subscribe

Environment

• Version used: 5.14.2
• Environment name and version: NodeJS v25.2.1
• Operating System and version (desktop or mobile): MacOS

This is exactly the kind of issue that makes mock tooling feel fine until the workflow gets real.

The initial request validates, but once the flow depends on a callback URL extracted from the request body, the integration path breaks. That’s a very different failure mode from “the endpoint returned the wrong shape” because it shows up after the first step, when one request starts driving the next one.

Really helpful repro here.