--dry-run option of pdm add still creates pdm.lock and empty __pypackages__

[astrojuanlu]

• I have searched the issue tracker and believe that this is not a duplicate.

The pdm add command advertises a --dry-run option saying

  --dry-run             Show the difference only and don't perform any action

however, passing it seems to still create a pdm.lock file and an empty __pypackages__ directory.

Steps to reproduce

mkdir /src && cd /src
ls -la
python3.9 -m venv .venv    
source .venv/bin/activate    
pip install pdm &> /dev/null          
pdm init -n        
pdm add -vv --dry-run "urllib3==1.25.7"    

Actual behavior

As you can see, pdm add -vv --dry-run "urllib3==1.25.7" adds a pdm.lock and __pypackages__, which I didn't expect.

$ docker run -it --rm python:3.9 bash
root@5a286c804de3:/# mkdir /src && cd /src
root@5a286c804de3:/src# ls -la
total 8
drwxr-xr-x 2 root root 4096 Feb 16 14:05 .
drwxr-xr-x 1 root root 4096 Feb 16 14:05 ..
root@5a286c804de3:/src# python3.9 -m venv .venv    
source .venv/bin/activate    
pip install pdm &> /dev/null          
pdm init -n        
Creating a pyproject.toml for PDM...
Using Python interpreter: /src/.venv/bin/python3.9 (3.9)
Changes are written to pyproject.toml.
(.venv) root@5a286c804de3:/src# ls -la
total 20
drwxr-xr-x 3 root root 4096 Feb 16 14:05 .
drwxr-xr-x 1 root root 4096 Feb 16 14:05 ..
-rw-r--r-- 1 root root   43 Feb 16 14:05 .pdm.toml
drwxr-xr-x 5 root root 4096 Feb 16 14:05 .venv
-rw-r--r-- 1 root root  286 Feb 16 14:05 pyproject.toml
(.venv) root@5a286c804de3:/src# pdm add -vv --dry-run "urllib3==1.25.7"    
Adding packages to default dependencies: urllib3
======== Start resolving requirements ========
  urllib3==1.25.7
  python>=3.9
  Adding requirement urllib3==1.25.7
	Found matching candidates:
	  <Candidate urllib3 1.25.7 from https://pypi.org/simple/urllib3/>
  Adding requirement python>=3.9
======== Starting round 0 ========
Resolving: new pin python >=3.9
======== Ending round 0 ========
======== Starting round 1 ========
Resolving: new pin urllib3 1.25.7
======== Ending round 1 ========
======== Starting round 2 ========
======== Resolution Result ========
Stable pins:
   python None
  urllib3 1.25.7
	Found matching candidates:
	  <Candidate urllib3 1.25.7 from https://pypi.org/simple/urllib3/>
🔒 Lock successful
Packages to add:
  - urllib3 1.25.7
(.venv) root@5a286c804de3:/src# ls -la
total 28
drwxr-xr-x 4 root root 4096 Feb 16 14:06 .
drwxr-xr-x 1 root root 4096 Feb 16 14:05 ..
-rw-r--r-- 1 root root   43 Feb 16 14:05 .pdm.toml
drwxr-xr-x 5 root root 4096 Feb 16 14:05 .venv
drwxr-xr-x 3 root root 4096 Feb 16 14:06 __pypackages__
-rw-r--r-- 1 root root  614 Feb 16 14:06 pdm.lock
-rw-r--r-- 1 root root  286 Feb 16 14:05 pyproject.toml

Expected behavior

--dry-run only shows output on the terminal, but doesn't do anything else (no new files, no new directories).

Environment Information

# pdm info && pdm info --env
PDM version:        1.12.8
Python Interpreter: /src/.venv/bin/python3.9 (3.9)
Project Root:       /src
Project Packages:   /src/__pypackages__/3.9
{
  "implementation_name": "cpython",
  "implementation_version": "3.9.10",
  "os_name": "posix",
  "platform_machine": "x86_64",
  "platform_release": "5.13.0-28-generic",
  "platform_system": "Linux",
  "platform_version": "#31~20.04.1-Ubuntu SMP Wed Jan 19 14:08:10 UTC 2022",
  "python_full_version": "3.9.10",
  "platform_python_implementation": "CPython",
  "python_version": "3.9",
  "sys_platform": "linux"
}