Copy module with option "decrypt: no" causes error when file already exists

[SteveWunderbar]

ISSUE TYPE

• Bug Report

COMPONENT NAME

Module: Copy
Option: decrypt: no #new in version 2.4.

ANSIBLE VERSION

ansible 2.4.0.0

OS / ENVIRONMENT

N/A

SUMMARY

When copying a (on the remote host non-existing) ansible-vault encrypted file with the copy module everything works fine and the copied file is encrypted (as it should be).
When the file already exists however, an error is thrown.

STEPS TO REPRODUCE

Run the following task twice to reproduce

---
- hosts: my-hosts
  tasks:
  - name: Copy vault-encrypted file
    copy:
      src: 'vault-encrypted.file'
      dest: .
      decrypt: no

  - name: Copy vault-encrypted file
    copy:
      src: 'vault-encrypted.file'
      dest: .
      decrypt: no

EXPECTED RESULTS

TASK [Copy vault-encrypted file] **********************************************************************************
changed: [my.server.com]

TASK [Copy vault-encrypted file] **********************************************************************************
ok: [my.server.com]

ACTUAL RESULTS

TASK [Copy vault-encrypted file] **********************************************************************************
changed: [my.server.com]

TASK [Copy vault-encrypted file] **********************************************************************************
fatal: [my.server.com]: FAILED! => {"changed": false, "checksum": "e88caee4fa8e6e905552d564e3d884097d8c67eb", "failed": true, "msg": "Unsupported parameters for (file) module: decrypt Supported parameters include: attributes,backup,content,delimiter,diff_peek,directory_mode,follow,force,group,mode,original_basename,owner,path,recurse,regexp,remote_src,selevel,serole,setype,seuser,src,state,unsafe_writes,validate"}

[guilim]

For info, same thing if decrypt: yes is used (not specific to decrypt: no)

If specified, the decrypt param seems to be passed to the file module by copy when the destination file already exists... but file does not support decrypt