"Failed to create conda environment" after the env is actually created — conda info --envs --json no longer returns envs_dirs (conda 26.x)

Inizia individuando l’helper env-dirs e i percorsi di cache-hit e cache-write di CONDA_PREFIXES_KEY descritti nell’issue. Confronta la risposta di conda info --envs --json con la risposta non filtrata, quindi verifica che la creazione di un ambiente risolva correttamente il suo prefix, eviti di mettere in cache un valore envs_dirs vuoto e non segnali più un falso errore.

Environment

Steps to reproduce

1. Python: Create Environment → Conda → Named (with an English display language).
2. Pick a Python version, enter a name (test).

Actual

conda itself succeeds — the output channel shows the whole transaction completing:

Preparing transaction: ...working... done
Verifying transaction: ...working... done
Executing transaction: ...working... done
#
# To activate this environment, use
#
#     $ conda activate test

and then the extension fails:

[info]    Using conda from cache: C:\Users\...\miniforge3\Library\bin\conda.BAT
[info]    Ran conda in 697: C:\Users\...\miniforge3\Library\bin\conda.BAT info --envs --json
[warning] conda info envs_dirs is undefined/null
[error]   Failed to create conda environment A system error occurred
          (ENOENT: no such file or directory, scandir
           'C:\Users\...\AppData\Local\Programs\Microsoft VS Code\conda-meta')

The environment is created and fully usable. Only the post-creation prefix lookup fails — but the user is shown Failed to create conda environment, which reads as though nothing was created.

Cause

The env-dirs helper calls conda info --envs --json and reads envs_dirs from it:

const e = await H(["info", "--envs", "--json"]);
const t = JSON.parse(e);
const n = t.envs_dirs;
return null == n
    ? (traceWarn("conda info envs_dirs is undefined/null"), { envs_dirs: [] })
    : Array.isArray(n)
    ? { envs_dirs: n }
    : { envs_dirs: [] };

As of conda 26.x, conda info --envs --json returns only envs and envs_details. envs_dirs is present only in the unfiltered conda info --json:

$ conda info --envs --json
{
  "envs": [
    "C:\\Users\\...\\miniforge3",
    "C:\\Users\\...\\miniforge3\\envs\\test",
    ...
  ],
  "envs_details": { ... }
}
# no envs_dirs key

$ conda info --json | findstr envs_dirs
  "envs_dirs": [ ... ]

So envs_dirs becomes []. The empty list makes the subsequent prefix search join an empty base path, and conda-meta ends up resolved relative to the process cwd — VS Code's own install directory — which is the ENOENT above.

Aggravating factor

The empty result is cached, and the cache-hit check accepts an empty array:

const n = await e.get(CONDA_PREFIXES_KEY);
if (n && Array.isArray(n)) return j = n, j;   // [] passes this check
...
j = n.envs_dirs;                              // []
await e.set(CONDA_PREFIXES_KEY, ...);         // and gets cached

Once it has failed, the bad [] is served from cache on later attempts, so the failure persists until the cache is cleared.

Suggested fix

• Read envs_dirs from conda info --json (or conda config --show envs_dirs --json) instead of conda info --envs --json.
• Better still, derive the new environment's prefix from the envs array that the same response already returns — it contains the full path of the environment that was just created.
• Treat an empty envs_dirs as a failure rather than a value: don't cache it, and require a non-empty array on the cache-hit path.