fix (shell) : Improve shell detection on windows (#3767)

- Currently we rely on `SHELL` environment variable for detecting
  active shell type. This will work when the environment variable is
  set. As per my observations, this environment variable is not set
  explicitly by various linux shell environments (`bash`,`zsh`,`fish`).
  We should detect currently active shell by checking currently active
  processes instead.
- While generating statements for export statements on Windows, we shall
  make sure that we have converted windows paths to linux paths.

Signed-off-by: Rohan Kumar <[email protected]>

Author: rohanKanojia

pkg/os/shell/shell.go

@@ -2,7 +2,16 @@ package shell
 
 import (
 	"fmt"
+	"os"
+	"strconv"
 	"strings"
+
+	crcos "github.com/crc-org/crc/v2/pkg/os"
+)
+
+var (
+	CommandRunner                           = crcos.NewLocalCommandRunner()
+	WindowsSubsystemLinuxKernelMetadataFile = "/proc/version"
 )
 
 type Config struct {
@@ -65,9 +74,9 @@ func GetEnvString(userShell string, envName string, envValue string) string {
 	case "cmd":
 		return fmt.Sprintf("SET %s=%s", envName, envValue)
 	case "fish":
-		return fmt.Sprintf("contains %s $fish_user_paths; or set -U fish_user_paths %s $fish_user_paths", envValue, envValue)
+		return fmt.Sprintf("contains %s $fish_user_paths; or set -U fish_user_paths %s $fish_user_paths", convertToLinuxStylePath(userShell, envValue), convertToLinuxStylePath(userShell, envValue))
 	default:
-		return fmt.Sprintf("export %s=\"%s\"", envName, envValue)
+		return fmt.Sprintf("export %s=\"%s\"", envName, convertToLinuxStylePath(userShell, envValue))
 	}
 }
 
@@ -81,8 +90,140 @@ func GetPathEnvString(userShell string, prependedPath string) string {
 	case "cmd":
 		pathStr = fmt.Sprintf("%s;%%PATH%%", prependedPath)
 	default:
-		pathStr = fmt.Sprintf("%s:$PATH", prependedPath)
+		pathStr = fmt.Sprintf("%s:$PATH", convertToLinuxStylePath(userShell, prependedPath))
 	}
 
 	return GetEnvString(userShell, "PATH", pathStr)
 }
+
+// convertToLinuxStylePath is a utility method to translate Windows paths to Linux environments (e.g. Git Bash).
+//
+// It receives two arguments:
+// - userShell : currently active shell
+// - path : Windows path to be converted
+//
+// It returns Linux equivalent of the Windows path.
+//
+// For example, a Windows path like `C:\Users\foo\.crc\bin\oc` is converted into `/C/Users/foo/.crc/bin/oc`.
+func convertToLinuxStylePath(userShell string, path string) string {
+	if IsWindowsSubsystemLinux() {
+		return convertToWindowsSubsystemLinuxPath(path)
+	}
+	if strings.Contains(path, "\\") &&
+		(userShell == "bash" || userShell == "zsh" || userShell == "fish") {
+		path = strings.ReplaceAll(path, ":", "")
+		path = strings.ReplaceAll(path, "\\", "/")
+
+		return fmt.Sprintf("/%s", path)
+	}
+	return path
+}
+
+// convertToWindowsSubsystemLinuxPath is a utility method to translate between Windows and WSL(Windows Subsystem for
+// Linux) paths. It relies on `wslpath` command to perform this conversion.
+//
+// It receives one argument:
+// - path : Windows path to be converted to WSL path
+//
+// It returns translated WSL equivalent of provided windows path.
+func convertToWindowsSubsystemLinuxPath(path string) string {
+	stdOut, _, err := CommandRunner.Run("wsl", "-e", "bash", "-c", fmt.Sprintf("wslpath -a '%s'", path))
+	if err != nil {
+		return path
+	}
+	return strings.TrimSpace(stdOut)
+}
+
+// IsWindowsSubsystemLinux detects whether current system is using Windows Subsystem for Linux or not
+//
+// It checks for these conditions to make sure that current system has WSL installed:
+// - `/proc/version` file is present
+// - `/proc/version` file contents contain keywords `Microsoft` and `WSL`
+//
+// It above conditions are met, then this method returns `true` otherwise `false`.
+func IsWindowsSubsystemLinux() bool {
+	procVersionContent, err := os.ReadFile(WindowsSubsystemLinuxKernelMetadataFile)
+	if err != nil {
+		return false
+	}
+	if strings.Contains(string(procVersionContent), "Microsoft") ||
+		strings.Contains(string(procVersionContent), "WSL") {
+		return true
+	}
+	return false
+}
+
+// detectShellByInvokingCommand is a utility method that tries to detect current shell in use by invoking `ps` command.
+// This method is extracted so that it could be used by unix systems as well as Windows (in case of WSL). It executes
+// the command provided in the method arguments and then passes the output to inspectProcessOutputForRecentlyUsedShell
+// for evaluation.
+//
+// It receives two arguments:
+// - defaultShell : default shell to revert back to in case it's unable to detect.
+// - command: command to be executed
+// - args: a string array containing command arguments
+//
+// It returns a string value representing current shell.
+func detectShellByInvokingCommand(defaultShell string, command string, args []string) string {
+	stdOut, _, err := CommandRunner.Run(command, args...)
+	if err != nil {
+		return defaultShell
+	}
+
+	detectedShell := inspectProcessOutputForRecentlyUsedShell(stdOut)
+	if detectedShell == "" {
+		return defaultShell
+	}
+	return detectedShell
+}
+
+// inspectProcessOutputForRecentlyUsedShell inspects output of ps command to detect currently active shell session.
+//
+// Note : This method assumes that ps command has already sorted the processes by `pid` in reverse order.
+// It parses the output into a struct, filters process types by name and returns the first element.
+//
+// It takes one argument:
+//
+// - psCommandOutput: output of ps command executed on a particular shell session
+//
+// It returns:
+//
+//   - a string value (one of `zsh`, `bash` or `fish`) for current shell environment in use. If it's not able to determine
+//     underlying shell type, it returns and empty string.
+//
+// This method tries to check all processes open and filters out shell sessions (one of `zsh`, `bash` or `fish)
+// It then returns first shell process.
+//
+// For example, if ps command gives this output:
+//
+//	2908 ps
+//	2889 fish
+//	823 bash
+//
+// Then this method would return `fish` as it's the first shell process.
+func inspectProcessOutputForRecentlyUsedShell(psCommandOutput string) string {
+	type ProcessOutput struct {
+		processID int
+		output    string
+	}
+	var processOutputs []ProcessOutput
+	lines := strings.Split(psCommandOutput, "\n")
+	for _, line := range lines {
+		lineParts := strings.Split(strings.TrimSpace(line), " ")
+		if len(lineParts) == 2 && (strings.Contains(lineParts[1], "zsh") ||
+			strings.Contains(lineParts[1], "bash") ||
+			strings.Contains(lineParts[1], "fish")) {
+			parsedProcessID, err := strconv.Atoi(lineParts[0])
+			if err == nil {
+				processOutputs = append(processOutputs, ProcessOutput{
+					processID: parsedProcessID,
+					output:    lineParts[1],
+				})
+			}
+		}
+	}
+	if len(processOutputs) > 0 {
+		return processOutputs[0].output
+	}
+	return ""
+}