Non-zero exit code for ERROR: pip's dependency resolver does not currently take into account all the packages that are installed?

Description

I’ve got two packages:

• package A (with transitive dependency B<N) in requirements file first.txt
• package C (with transitive dependency B>N) in requirements file second.txt

So basically the transitive dependencies for both A and C are the same package but of conflicting versions.

If I do the following:

• pip install --no-cache-dir -r first.txt
• pip install --no-cache-dir -r second.txt

I do:

• see an error ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts. in stderr when installing second.txt
• BUT despite the error pip install successfully installs conflicting transitive dependency B>N
• pip install also returns exit code 0

Expected behavior

pip install --no-cache-dir -r second.txt should throw ERROR: ResolutionImpossible and returns exit code 1 (or whatever non-zero code it should return).

Another (less attractive than the previous one) option would be just returning non-zero exit code for ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. Because it’s an error, not a warning.

pip version

21.2.4

Python version

3.9.6

OS

Ubuntu 21.04, Alpine 3.14

How to Reproduce

My setup is a virtualenv with the following versions:

(pip-separate-no-cache-dir) ➜  pip-bug python --version
Python 3.9.6

(pip-separate-no-cache-dir) ➜  pip-bug pip --version
pip 21.2.4 from /home/vitaly/.pyenv/versions/3.9.6/envs/pip-separate-no-cache-dir/lib/python3.9/site-packages/pip (python 3.9)

The content of the requirement files:

(pip-separate-no-cache-dir) ➜  pip-bug cat first.txt
aiohttp-apispec==2.2.1  # webargs<6

(pip-separate-no-cache-dir) ➜  pip-bug cat second.txt
webargs-sanic==2.0.0    # webargs >=7.0.1

Steps to reproduce:

1. pip install --no-cache-dir -r first.txt
2. pip install --no-cache-dir -r second.txt
3. echo $?
4. pip check

Output

Installing the first requirement file:


(pip-separate-no-cache-dir) ➜  pip-bug pip install --no-cache-dir -r first.txt
Collecting aiohttp-apispec==2.2.1
  Downloading aiohttp-apispec-2.2.1.tar.gz (2.3 MB)
     |████████████████████████████████| 2.3 MB 2.5 MB/s
Collecting aiohttp<4.0,>=3.0.1
  Downloading aiohttp-3.7.4.post0-cp39-cp39-manylinux2014_x86_64.whl (1.4 MB)
     |████████████████████████████████| 1.4 MB 13.7 MB/s
Collecting apispec<4.0,>=3.0.0
  Downloading apispec-3.3.2-py2.py3-none-any.whl (27 kB)
Collecting webargs<6.0
  Downloading webargs-5.5.3-py3-none-any.whl (29 kB)
Collecting jinja2<3.0
  Downloading Jinja2-2.11.3-py2.py3-none-any.whl (125 kB)
     |████████████████████████████████| 125 kB 11.8 MB/s
Collecting multidict<7.0,>=4.5
  Downloading multidict-5.1.0-cp39-cp39-manylinux2014_x86_64.whl (151 kB)
     |████████████████████████████████| 151 kB 10.5 MB/s
Collecting async-timeout<4.0,>=3.0
  Downloading async_timeout-3.0.1-py3-none-any.whl (8.2 kB)
Collecting typing-extensions>=3.6.5
  Downloading typing_extensions-3.10.0.0-py3-none-any.whl (26 kB)
Collecting attrs>=17.3.0
  Downloading attrs-21.2.0-py2.py3-none-any.whl (53 kB)
     |████████████████████████████████| 53 kB 12.8 MB/s
Collecting yarl<2.0,>=1.0
  Downloading yarl-1.6.3-cp39-cp39-manylinux2014_x86_64.whl (315 kB)
     |████████████████████████████████| 315 kB 11.5 MB/s
Collecting chardet<5.0,>=2.0
  Downloading chardet-4.0.0-py2.py3-none-any.whl (178 kB)
     |████████████████████████████████| 178 kB 11.2 MB/s
Collecting MarkupSafe>=0.23
  Downloading MarkupSafe-2.0.1-cp39-cp39-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl (30 kB)
Collecting marshmallow>=2.15.2
  Downloading marshmallow-3.13.0-py2.py3-none-any.whl (47 kB)
     |████████████████████████████████| 47 kB 19.4 MB/s
Collecting idna>=2.0
  Downloading idna-3.2-py3-none-any.whl (59 kB)
     |████████████████████████████████| 59 kB 17.1 MB/s
Using legacy 'setup.py install' for aiohttp-apispec, since package 'wheel' is not installed.
Installing collected packages: multidict, idna, yarl, typing-extensions, marshmallow, MarkupSafe, chardet, attrs, async-timeout, webargs, jinja2, apispec, aiohttp, aiohttp-apispec
    Running setup.py install for aiohttp-apispec ... done
Successfully installed MarkupSafe-2.0.1 aiohttp-3.7.4.post0 aiohttp-apispec-2.2.1 apispec-3.3.2 async-timeout-3.0.1 attrs-21.2.0 chardet-4.0.0 idna-3.2 jinja2-2.11.3 marshmallow-3.13.0 multidict-5.1.0 typing-extensions-3.10.0.0 webargs-5.5.3 yarl-1.6.3

(pip-separate-no-cache-dir) ➜  pip-bug echo $?
0

(pip-separate-no-cache-dir) ➜  pip-bug pip check
No broken requirements found.

(pip-separate-no-cache-dir) ➜  pip-bug

Installing the second requirement file

(pip-separate-no-cache-dir) ➜  pip-bug pip install --no-cache-dir -r second.txt
Collecting webargs-sanic==2.0.0
  Downloading webargs-sanic-2.0.0.tar.gz (5.8 kB)
Collecting sanic>=0.8.3
  Downloading sanic-21.6.2-py3-none-any.whl (94 kB)
     |████████████████████████████████| 94 kB 2.4 MB/s
Collecting webargs>=7.0.1
  Downloading webargs-8.0.1-py3-none-any.whl (30 kB)
Collecting httptools>=0.0.10
  Downloading httptools-0.3.0-cp39-cp39-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_12_x86_64.manylinux2010_x86_64.whl (428 kB)
     |████████████████████████████████| 428 kB 5.5 MB/s
Collecting aiofiles>=0.6.0
  Downloading aiofiles-0.7.0-py3-none-any.whl (13 kB)
Collecting sanic-routing~=0.7
  Downloading sanic_routing-0.7.1-py3-none-any.whl (23 kB)
Collecting websockets>=9.0
  Downloading websockets-9.1-cp39-cp39-manylinux2010_x86_64.whl (102 kB)
     |████████████████████████████████| 102 kB 544 kB/s
Collecting uvloop>=0.5.3
  Downloading uvloop-0.16.0-cp39-cp39-manylinux_2_12_x86_64.manylinux2010_x86_64.whl (4.3 MB)
     |████████████████████████████████| 4.3 MB 8.1 MB/s
Collecting ujson>=1.35
  Downloading ujson-4.1.0-cp39-cp39-manylinux_2_5_x86_64.manylinux1_x86_64.whl (179 kB)
     |████████████████████████████████| 179 kB 11.0 MB/s
Requirement already satisfied: multidict<6.0,>=5.0 in /home/vitaly/.pyenv/versions/3.9.6/envs/pip-separate-no-cache-dir/lib/python3.9/site-packages (from sanic>=0.8.3->webargs-sanic==2.0.0->-r second.txt (line 1)) (5.1.0)
Requirement already satisfied: marshmallow>=3.0.0 in /home/vitaly/.pyenv/versions/3.9.6/envs/pip-separate-no-cache-dir/lib/python3.9/site-packages (from webargs>=7.0.1->webargs-sanic==2.0.0->-r second.txt (line 1)) (3.13.0)
Using legacy 'setup.py install' for webargs-sanic, since package 'wheel' is not installed.
Installing collected packages: websockets, uvloop, ujson, sanic-routing, httptools, aiofiles, webargs, sanic, webargs-sanic
  Attempting uninstall: webargs
    Found existing installation: webargs 5.5.3
    Uninstalling webargs-5.5.3:
      Successfully uninstalled webargs-5.5.3
    Running setup.py install for webargs-sanic ... done
ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts.
aiohttp-apispec 2.2.1 requires webargs<6.0, but you have webargs 8.0.1 which is incompatible.
Successfully installed aiofiles-0.7.0 httptools-0.3.0 sanic-21.6.2 sanic-routing-0.7.1 ujson-4.1.0 uvloop-0.16.0 webargs-8.0.1 webargs-sanic-2.0.0 websockets-9.1

(pip-separate-no-cache-dir) ➜  pip-bug echo $?
0

# with or without --no-cache-dir option, pip check detects the problem
(pip-separate-no-cache-dir) ➜  pip-bug pip check
aiohttp-apispec 2.2.1 has requirement webargs<6.0, but you have webargs 8.0.1.

All in all, the ERROR: pip's dependency resolver does not currently take into account all the packages that are installed. This behaviour is the source of the following dependency conflicts. is thrown to stderr, but exit code is 0 and installation is successful.

I do understand that error says precisely that the pip couldn’t properly resolve as not all package versions being taken into consideration. But still it is not a warning, but an error, so why exit code is 0?

Also, pip check does detect the problem after the installation.

By the way, for some cases if no --no-cache-dir option is used, pip throws proper ERROR: ResolutionImpossible, although I cannot reproduce the behaviour for the current exemple requirement files.

If both requirements combined into one, then resolution confict is detected correctly, non-zero exit code is returned as expected:

(pip-single) ➜  pip-bug cat single.txt
aiohttp-apispec==2.2.1  # webargs<6
webargs-sanic==2.0.0    # webargs >=7.0.1

(pip-single) ➜  pip-bug pip install --no-cache-dir -r single.txt
Collecting aiohttp-apispec==2.2.1
  Downloading aiohttp-apispec-2.2.1.tar.gz (2.3 MB)
     |████████████████████████████████| 2.3 MB 1.9 MB/s
Collecting webargs-sanic==2.0.0
  Downloading webargs-sanic-2.0.0.tar.gz (5.8 kB)
Collecting aiohttp<4.0,>=3.0.1
  Downloading aiohttp-3.7.4.post0-cp39-cp39-manylinux2014_x86_64.whl (1.4 MB)
     |████████████████████████████████| 1.4 MB 13.5 MB/s
Collecting apispec<4.0,>=3.0.0
  Downloading apispec-3.3.2-py2.py3-none-any.whl (27 kB)
Collecting webargs<6.0
  Downloading webargs-5.5.3-py3-none-any.whl (29 kB)
Collecting jinja2<3.0
  Downloading Jinja2-2.11.3-py2.py3-none-any.whl (125 kB)
     |████████████████████████████████| 125 kB 11.0 MB/s
Collecting sanic>=0.8.3
  Downloading sanic-21.6.2-py3-none-any.whl (94 kB)
     |████████████████████████████████| 94 kB 13.9 MB/s
INFO: pip is looking at multiple versions of aiohttp-apispec to determine which version is compatible with other requirements. This could take a while.
ERROR: Cannot install -r single.txt (line 1) and -r single.txt (line 2) because these package versions have conflicting dependencies.

The conflict is caused by:
    aiohttp-apispec 2.2.1 depends on webargs<6.0
    webargs-sanic 2.0.0 depends on webargs>=7.0.1

To fix this you could try to:
1. loosen the range of package versions you've specified
2. remove package versions to allow pip attempt to solve the dependency conflict

ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/user_guide/#fixing-conflicting-dependencies
(pip-single) ➜  pip-bug echo $?
1
(pip-single) ➜  pip-bug pip check
No broken requirements found.

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[pradyunsg]

Coolieo. I’m gonna consolidate this into #9094 now; I think the intended next steps are documented there, and you’ve got a working setup until then. 😃

[uranusjr]

Unfortunately there are way too many people depending on pip returning 0 in this case, we can’t just change it. The return code predates the message by a loooooong time.