Fix finding Python within virtualenv on Windows

.github/workflows/push.yml

@@ -40,6 +40,9 @@ jobs:
         with:
           python-version: '3.9'
 
+      - name: Install uv
+        uses: astral-sh/setup-uv@v4
+
       - name: Set go env
         run: |
           echo "GOPATH=$(go env GOPATH)" >> $GITHUB_ENV

libs/python/detect.go

@@ -25,15 +25,32 @@ func DetectExecutable(ctx context.Context) (string, error) {
 	// the parent directory tree.
 	//
 	// See https://github.com/pyenv/pyenv#understanding-python-version-selection
+
+	// On Windows when virtualenv is created, the <env>/Scripts directory
+	// contains python.exe but no python3.exe. However, system python does have python3 entry
+	// and it is also added to PATH, so it is found first.
+	if runtime.GOOS == "windows" {
+		out, err := exec.LookPath("python")
+		if err == nil && out != "" {
+			return out, nil
+		}
+		if err != nil && !errors.Is(err, exec.ErrNotFound) {
+			return "", err
+		}
+	}
+
 	out, err := exec.LookPath("python3")
+
 	// most of the OS'es have python3 in $PATH, but for those which don't,
 	// we perform the latest version lookup
 	if err != nil && !errors.Is(err, exec.ErrNotFound) {
 		return "", err
 	}
+
 	if out != "" {
 		return out, nil
 	}
+
 	// otherwise, detect all interpreters and pick the least that satisfies
 	// minimal version requirements
 	all, err := DetectInterpreters(ctx)

libs/python/pythontest/pythontest.go

@@ -0,0 +1,115 @@
+package pythontest
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/databricks/cli/internal/testutil"
+	"github.com/databricks/cli/libs/python"
+	"github.com/stretchr/testify/require"
+)
+
+type VenvOpts struct {
+	// input
+	PythonVersion    string
+	skipVersionCheck bool
+
+	// input/output
+	Dir  string
+	Name string
+
+	// output:
+	// Absolute path to venv
+	EnvPath string
+
+	// Absolute path to venv/bin or venv/Scripts, depending on OS
+	BinPath string
+
+	// Absolute path to python binary
+	PythonExe string
+}
+
+func CreatePythonEnv(opts *VenvOpts) error {
+	if opts == nil || opts.PythonVersion == "" {
+		return errors.New("PythonVersion must be provided")
+	}
+	if opts.Name == "" {
+		opts.Name = testutil.RandomName("test-venv-")
+	}
+	if opts.Dir != "" {
+		opts.Dir = "."
+	}
+
+	cmd := exec.Command("uv", "venv", opts.Name, "--python", opts.PythonVersion, "--seed", "-q")
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	cmd.Dir = opts.Dir
+	err := cmd.Run()
+	if err != nil {
+		return err
+	}
+
+	opts.EnvPath, err = filepath.Abs(filepath.Join(opts.Dir, opts.Name))
+	if err != nil {
+		return err
+	}
+
+	_, err = os.Stat(opts.EnvPath)
+	if err != nil {
+		return fmt.Errorf("cannot stat EnvPath %s: %s", opts.EnvPath, err)
+	}
+
+	if runtime.GOOS == "windows" {
+		// https://github.com/pypa/virtualenv/commit/993ba1316a83b760370f5a3872b3f5ef4dd904c1
+		opts.BinPath = filepath.Join(opts.EnvPath, "Scripts")
+		opts.PythonExe = filepath.Join(opts.BinPath, "python.exe")
+	} else {
+		opts.BinPath = filepath.Join(opts.EnvPath, "bin")
+		opts.PythonExe = filepath.Join(opts.BinPath, "python3")
+	}
+
+	_, err = os.Stat(opts.BinPath)
+	if err != nil {
+		return fmt.Errorf("cannot stat BinPath %s: %s", opts.BinPath, err)
+	}
+
+	_, err = os.Stat(opts.PythonExe)
+	if err != nil {
+		return fmt.Errorf("cannot stat PythonExe %s: %s", opts.PythonExe, err)
+	}
+
+	if !opts.skipVersionCheck {
+		cmd := exec.Command(opts.PythonExe, "--version")
+		out, err := cmd.CombinedOutput()
+		if err != nil {
+			return fmt.Errorf("Failed to run %s --version: %s", opts.PythonExe, err)
+		}
+		outString := string(out)
+		expectVersion := "Python " + opts.PythonVersion
+		if !strings.HasPrefix(outString, expectVersion) {
+			return fmt.Errorf("Unexpected output from %s --version: %v (expected %v)", opts.PythonExe, outString, expectVersion)
+		}
+	}
+
+	return nil
+}
+
+func RequireActivatedPythonEnv(t *testing.T, ctx context.Context, opts *VenvOpts) {
+	err := CreatePythonEnv(opts)
+	require.NoError(t, err)
+	require.DirExists(t, opts.BinPath)
+
+	newPath := fmt.Sprintf("%s%c%s", opts.BinPath, os.PathListSeparator, os.Getenv("PATH"))
+	t.Setenv("PATH", newPath)
+
+	pythonExe, err := python.DetectExecutable(ctx)
+	require.NoError(t, err)
+	require.Equal(t, filepath.Dir(pythonExe), filepath.Dir(opts.PythonExe))
+}

libs/python/pythontest/pythontest_test.go

@@ -0,0 +1,31 @@
+package pythontest
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestVenvSuccess(t *testing.T) {
+	// Test at least two version to ensure we capture a case where venv version does not match system one
+	for _, pythonVersion := range []string{"3.11", "3.12"} {
+		t.Run(pythonVersion, func(t *testing.T) {
+			ctx := context.Background()
+			opts := VenvOpts{PythonVersion: pythonVersion}
+			RequireActivatedPythonEnv(t, ctx, &opts)
+			require.DirExists(t, opts.EnvPath)
+			require.DirExists(t, opts.BinPath)
+			require.FileExists(t, opts.PythonExe)
+		})
+	}
+}
+
+func TestWrongVersion(t *testing.T) {
+	require.Error(t, CreatePythonEnv(&VenvOpts{PythonVersion: "4.0"}))
+}
+
+func TestMissingVersion(t *testing.T) {
+	require.Error(t, CreatePythonEnv(nil))
+	require.Error(t, CreatePythonEnv(&VenvOpts{}))
+}