Fix PyEnv Windows path calculation for environment grouping (#1210)

- [x] Fix `nativeToPythonEnv` in `pyenvUtils.ts` - extract `getPyenvDir`
helper
- [x] Address reviewer feedback: use `PYENV_ROOT` env var as primary
source, revert 3-levels-up to 2-levels-up (old behavior was correct for
pyenv-win since versions live under `~/.pyenv/pyenv-win/versions/`)
- [x] Fix POSIX test to use absolute path with `path.sep`
- [x] Add test for `PYENV_ROOT` preference
- [x] Validate changes compile and all 583 tests pass (no regressions)
- [x] Run code review and security scan

<!-- START COPILOT ORIGINAL PROMPT -->



<details>

<summary>Original prompt</summary>

> 
> ----
> 
> *This section details on the original issue you should resolve*
> 
> <issue_title>PyEnv: Windows path calculation bug causes environment
grouping to fail</issue_title>
> <issue_description>## Problem
> 
> In `pyenvUtils.ts`, the calculation of `versionsPath` and `envsPaths`
is incorrect on Windows due to the pyenv-win directory structure.
> 
> ### Current Code
> ```typescript
> // pyenvUtils.ts L128-130
> const versionsPath =
normalizePath(path.join(path.dirname(path.dirname(pyenv)), 'versions'));
> const envsPaths = normalizePath(path.join(path.dirname(versionsPath),
'envs'));
> ```
> 
> ### Issue
> On Windows, pyenv is located at `~/.pyenv/pyenv-win/bin/pyenv.bat`.
The current logic calculates:
> - `path.dirname(path.dirname(pyenv))` → `~/.pyenv/pyenv-win` ❌
> - Should be `~/.pyenv` to find `versions` folder properly
> 
> This causes:
> 1. Environment grouping (`PYENV_VERSIONS` vs `PYENV_ENVIRONMENTS`) to
fail
> 2. Environments not being associated with the correct manager
> 
> ### PET Server Reference
> The PET server handles this correctly with platform-specific code in
`pet-pyenv/src/environment_locations.rs`:
> ```rust
> #[cfg(windows)]
> pub fn get_home_pyenv_dir(env_vars: &EnvVariables) -> Option<PathBuf>
{
>     let home = env_vars.home.clone()?;
>     Some(norm_case(home.join(".pyenv").join("pyenv-win")))
> }
> ```
> 
> ### Suggested Fix
> Add Windows-specific handling when calculating the versions and envs
paths:
> ```typescript
> const pyenvDir = isWindows() 
> ? path.dirname(path.dirname(path.dirname(pyenv))) // Go up 3 levels on
Windows
>     : path.dirname(path.dirname(pyenv));
> const versionsPath = normalizePath(path.join(pyenvDir, 'versions'));
> ```
> 
> ### Affected File
> `src/managers/pyenv/pyenvUtils.ts`</issue_description>
> 
> ## Comments on the Issue (you are @copilot in this section)
> 
> <comments>
> </comments>
> 


</details>



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- Fixes #1180

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: karthiknadig <3840081+karthiknadig@users.noreply.github.com>

Author: Copilot

src/managers/pyenv/pyenvUtils.ts

@@ -23,6 +23,21 @@ import {
 } from '../common/nativePythonFinder';
 import { shortVersion, sortEnvironments } from '../common/utils';
 
+/**
+ * Returns the pyenv root directory from the pyenv executable path.
+ * Prefers `PYENV_ROOT` env var when set, otherwise goes up 2 levels from the binary.
+ * On POSIX, pyenv binary is at `<root>/bin/pyenv` (e.g. `~/.pyenv/bin/pyenv`).
+ * On Windows, pyenv-win binary is at `<root>/bin/pyenv.bat` (e.g. `~/.pyenv/pyenv-win/bin/pyenv.bat`,
+ * where `<root>` is `~/.pyenv/pyenv-win`).
+ */
+export function getPyenvDir(pyenv: string): string {
+    const pyenvRoot = process.env.PYENV_ROOT;
+    if (pyenvRoot) {
+        return pyenvRoot;
+    }
+    return path.dirname(path.dirname(pyenv));
+}
+
 async function findPyenv(): Promise<string | undefined> {
     try {
         return await which('pyenv');
@@ -174,8 +189,9 @@ function nativeToPythonEnv(
         return undefined;
     }
 
-    const versionsPath = normalizePath(path.join(path.dirname(path.dirname(pyenv)), 'versions'));
-    const envsPaths = normalizePath(path.join(path.dirname(versionsPath), 'envs'));
+    const pyenvDir = getPyenvDir(pyenv);
+    const versionsPath = normalizePath(path.join(pyenvDir, 'versions'));
+    const envsPaths = normalizePath(path.join(pyenvDir, 'envs'));
     let group = undefined;
     const normPrefix = normalizePath(info.prefix);
     if (normPrefix.startsWith(versionsPath)) {

src/test/managers/pyenv/pyenvUtils.unit.test.ts

@@ -0,0 +1,44 @@
+import assert from 'node:assert';
+import * as path from 'path';
+import * as sinon from 'sinon';
+import { getPyenvDir } from '../../../managers/pyenv/pyenvUtils';
+
+suite('pyenvUtils - getPyenvDir', () => {
+    let originalPyenvRoot: string | undefined;
+
+    setup(() => {
+        originalPyenvRoot = process.env.PYENV_ROOT;
+        delete process.env.PYENV_ROOT;
+    });
+
+    teardown(() => {
+        sinon.restore();
+        if (originalPyenvRoot !== undefined) {
+            process.env.PYENV_ROOT = originalPyenvRoot;
+        } else {
+            delete process.env.PYENV_ROOT;
+        }
+    });
+
+    test('should use PYENV_ROOT when set', () => {
+        const pyenvRoot = path.join(path.sep, 'custom', 'pyenv', 'root');
+        process.env.PYENV_ROOT = pyenvRoot;
+        const pyenvBin = path.join(path.sep, 'other', 'bin', 'pyenv');
+        const result = getPyenvDir(pyenvBin);
+        assert.strictEqual(result, pyenvRoot);
+    });
+
+    test('should go up 2 levels on POSIX when PYENV_ROOT is not set (bin/pyenv -> pyenv root)', () => {
+        // e.g. /home/user/.pyenv/bin/pyenv
+        const pyenvBin = path.join(path.sep, 'home', 'user', '.pyenv', 'bin', 'pyenv');
+        const result = getPyenvDir(pyenvBin);
+        assert.strictEqual(result, path.join(path.sep, 'home', 'user', '.pyenv'));
+    });
+
+    test('should go up 2 levels on Windows when PYENV_ROOT is not set (pyenv-win/bin/pyenv.bat -> pyenv-win)', () => {
+        // e.g. C:\Users\user\.pyenv\pyenv-win\bin\pyenv.bat -> C:\Users\user\.pyenv\pyenv-win
+        const pyenvBin = path.join('C:', 'Users', 'user', '.pyenv', 'pyenv-win', 'bin', 'pyenv.bat');
+        const result = getPyenvDir(pyenvBin);
+        assert.strictEqual(result, path.join('C:', 'Users', 'user', '.pyenv', 'pyenv-win'));
+    });
+});