[Windows-Compatibilty-feature] - Initial changes to add Powershell sc…

…ript as an alternative to grep

provider/internal/builtin/service_client.go

@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"regexp"
+	"runtime"
 	"strconv"
 	"strings"
 	"sync"
@@ -83,14 +84,12 @@ func (p *builtinServiceClient) Evaluate(ctx context.Context, cap string, conditi
 		if c.Pattern == "" {
 			return response, fmt.Errorf("could not parse provided regex pattern as string: %v", conditionInfo)
 		}
+
 		var outputBytes []byte
-		grep := exec.Command("grep", "-o", "-n", "-R", "-P", c.Pattern, p.config.Location)
-		outputBytes, err := grep.Output()
+		//Runs on Windows using PowerShell.exe and Unix based systems using grep
+		outputBytes, err := runOSSpecificGrepCommand(c.Pattern, p.config.Location)
 		if err != nil {
-			if exitError, ok := err.(*exec.ExitError); ok && exitError.ExitCode() == 1 {
-				return response, nil
-			}
-			return response, fmt.Errorf("could not run grep with provided pattern %+v", err)
+			return response, err
 		}
 
 		matches := []string{}
@@ -100,13 +99,10 @@ func (p *builtinServiceClient) Evaluate(ctx context.Context, cap string, conditi
 		}
 
 		for _, match := range matches {
-			//TODO(fabianvf): This will not work if there is a `:` in the filename, do we care?
-			pieces := strings.SplitN(match, ":", 3)
-			if len(pieces) != 3 {
-				//TODO(fabianvf): Just log or return?
-				//(shawn-hurley): I think the return is good personally
-				return response, fmt.Errorf(
-					"malformed response from grep, cannot parse grep output '%s' with pattern {filepath}:{lineNumber}:{matchingText}", match)
+			var pieces []string
+			pieces, err := parseGrepOutputForFileContent(match)
+			if err != nil {
+				return response, fmt.Errorf("could not parse grep output '%s' for the Pattern '%v': %v ", match, c.Pattern, err)
 			}
 
 			containsFile, err := provider.FilterFilePattern(c.FilePattern, pieces[0])
@@ -130,6 +126,7 @@ func (p *builtinServiceClient) Evaluate(ctx context.Context, cap string, conditi
 			if err != nil {
 				return response, fmt.Errorf("cannot convert line number string to integer")
 			}
+
 			response.Incidents = append(response.Incidents, provider.IncidentContext{
 				FileURI:    uri.File(absPath),
 				LineNumber: &lineNumber,
@@ -497,3 +494,60 @@ func (b *builtinServiceClient) isFileIncluded(absolutePath string) bool {
 	b.log.V(7).Info("excluding file from search", "file", absolutePath)
 	return false
 }
+
+func parseGrepOutputForFileContent(match string) ([]string, error) {
+	// This will parse the output of the PowerShell/grep in the form
+	// "Filepath:Linenumber:Matchingtext" to return string array of path, line number and matching text
+	// works with handling both windows and unix based file paths eg: "C:\path\to\file" and "/path/to/file"
+	re, err := regexp.Compile(`^(.*?):(\d+):(.*)$`)
+	if err != nil {
+		return nil, fmt.Errorf("failed to compile regular expression: %v", err)
+	}
+	submatches := re.FindStringSubmatch(match)
+	if len(submatches) != 4 {
+		return nil, fmt.Errorf(
+			"malformed response from file search, cannot parse result '%s' with pattern %#q", match, re)
+	}
+	return submatches[1:], nil
+}
+
+func runOSSpecificGrepCommand(pattern string, location string) ([]byte, error) {
+	var outputBytes []byte
+	var err error
+	var utilName string
+
+	if runtime.GOOS == "windows" {
+		utilName = "powershell.exe"
+		// Windows does not have grep, so we use PowerShell.exe's Select-String instead
+		// This is a workaround until we can find a better solution
+		psScript := `
+		$pattern = $env:PATTERN
+		$location = $env:FILEPATH
+		Get-ChildItem -Path $location -Recurse -File | ForEach-Object {
+			$file = $_    
+			# Search for the pattern in the file
+			Select-String -Path $file.FullName -Pattern $pattern -AllMatches | ForEach-Object { 
+				foreach ($match in $_.Matches) { 
+					"{0}:{1}:{2}" -f $file.FullName, $_.LineNumber, $match.Value
+				} 
+			}
+		}`
+		findstr := exec.Command(utilName, "-Command", psScript)
+		findstr.Env = append(os.Environ(), "PATTERN="+pattern, "FILEPATH="+location)
+		outputBytes, err = findstr.Output()
+
+	} else {
+		utilName = "grep"
+		// Linux and MacOS use grep
+		grep := exec.Command(utilName, "-o", "-n", "-R", "-P", pattern, location)
+		outputBytes, err = grep.Output()
+	}
+	if err != nil {
+		if exitError, ok := err.(*exec.ExitError); ok && exitError.ExitCode() == 1 {
+			return nil, nil
+		}
+		return nil, fmt.Errorf("could not run '%s' with provided pattern %+v", utilName, err)
+	}
+
+	return outputBytes, nil
+}