--offline mode does not work if user has just cleaned the index cache

[jaimergp]

This is kind of a corner case.

% conda clean --index-cache
% mamba create  -n testtestre --offline python
...

    Traceback (most recent call last):
      File "/opt/conda-src/conda/exceptions.py", line 1085, in __call__
        return func(*args, **kwargs)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 927, in exception_converter
        raise e
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 921, in exception_converter
        exit_code = _wrapped_main(*args, **kwargs)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 879, in _wrapped_main
        result = do_call(args, p)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 761, in do_call
        exit_code = create(args, parser)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 664, in create
        return install(args, parser, "create")
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 534, in install
        index = load_channels(pool, channels, repos)
      File "/opt/conda/lib/python3.9/site-packages/mamba/utils.py", line 172, in load_channels
        with FileLock(subdir.cache_path()):
    RuntimeError: Cache not loaded!

....

---

If I use a different lock file by patching this line, we get a different error:

% mamba create -n test  --offline python
....
    Traceback (most recent call last):
      File "/opt/conda-src/conda/exceptions.py", line 1085, in __call__
        return func(*args, **kwargs)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 927, in exception_converter
        raise e
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 921, in exception_converter
        exit_code = _wrapped_main(*args, **kwargs)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 879, in _wrapped_main
        result = do_call(args, p)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 761, in do_call
        exit_code = create(args, parser)
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 664, in create
        return install(args, parser, "create")
      File "/opt/conda/lib/python3.9/site-packages/mamba/mamba.py", line 534, in install
        index = load_channels(pool, channels, repos)
      File "/opt/conda/lib/python3.9/site-packages/mamba/utils.py", line 174, in load_channels
        repo = subdir.create_repo(pool)
    RuntimeError: [json.exception.type_error.302] type must be string, but is null

[wolfv]

We have a function in mamba to create a repository from all things found in pkgs — but I'm not sure that would be the expected behavior. I think it should fail, right? Since we can't solve for the indicated channels.

[adriendelsalle]

@jaimergp the lock files were replaced by our implementation

I also don't get how to solve offline without an index file, could you please elaborate a bit on that?
Thx!

[jaimergp]

This reproduces the test found at https://github.com/conda/conda/blob/27c559cec875f61ccaad56817562ed0a42afc5f0/tests/test_create.py#L2342.

Let me know if you need more context!