uri: sourcing vaulted file doesn't work

SUMMARY

I'm using uri module to send the vaulted file, but Ansible doesn't decrypt it.

    uri:
      url: "http://localhost:8888/"
      method: POST
      src: file-encrypted.json

Instead, it's sending raw vault format, despite specifying --ask-vault-pass.

ISSUE TYPE

• Bug Report
• Feature Idea

COMPONENT NAME

uri

ANSIBLE VERSION

ansible 2.8.0

CONFIGURATION

n/a

OS / ENVIRONMENT

macOS

STEPS TO REPRODUCE

1. Create a file.json with {'foo': 'bar'} content.
2. Vault it via: ansible-vault encrypt file.json
3. Create the following playbook (e.g. uri.yml):

---
- hosts: localhost
  tasks:
  - name: Send JSON file
    uri:
      url: "http://localhost:8888/"
      method: POST
      src: file.json
      headers:
        Content-Type: "application/json"

4. On the other terminal, run the netcat on port 8888: nc -vl 8888.
5. Run playbook via: ansible-playbook uri.yml --ask-vault-pass -vvv

EXPECTED RESULTS

Original content of JSON file is sent.

ACTUAL RESULTS

Encrypted version is received instead:

$  nc -vl 8888
POST / HTTP/1.1
Accept-Encoding: identity
Host: localhost:8888
User-Agent: ansible-httpget
Content-Type: application/json
Content-Length: 355
Connection: close

$ANSIBLE_VAULT;1.1;AES256
39373739353265643239323865303463303638656538663366663330343835353834306462646232
3332326234303438396263663337646134393563333165640a616433366364666161366231326463