Panic when symlink loop encountered during project discovery

Even though the previous commit caused the project discovery code to gracefully avoid perpetual recursion when specific
configurations of symlinks are present in the linting target path, it turned out that the project data phase that comes
after is also not able to handle this correctly, and fixing that is more difficult since the incompatible code is in
Arduino CLI. So for now the provisional fix is to panic during the project discovery phase, which will at least avoid the
far worse behavior of a permanent hang.

Author: per1234

internal/project/project.go

@@ -134,7 +134,10 @@ func findProjectsUnderPath(targetPath *paths.Path, projectTypeFilter projecttype
 		return foundProjects
 	}
 
-	if recursive && symlinkDepth < 10 {
+	if recursive {
+		if symlinkDepth > 10 {
+			panic(fmt.Sprintf("symlink depth exceeded maximum while finding projects under %s", targetPath))
+		}
 		// targetPath was not a project, so search the subfolders.
 		directoryListing, _ := targetPath.ReadDir()
 		directoryListing.FilterDirs()

internal/project/project_test.go

@@ -20,7 +20,6 @@ import (
 	"os"
 	"reflect"
 	"testing"
-	"time"
 
 	"github.com/arduino/arduino-lint/internal/configuration"
 	"github.com/arduino/arduino-lint/internal/project/projecttype"
@@ -60,28 +59,7 @@ func TestSymlinkLoop(t *testing.T) {
 
 	configuration.Initialize(test.ConfigurationFlags(), []string{libraryPath.String()})
 
-	// The failure condition is FindProjects() never returning, testing for which requires setting up a timeout.
-	done := make(chan bool)
-	go func() {
-		_, err = FindProjects()
-		done <- true
-	}()
-
-	assert.Eventually(
-		t,
-		func() bool {
-			select {
-			case <-done:
-				return true
-			default:
-				return false
-			}
-		},
-		20*time.Second,
-		10*time.Millisecond,
-		"Infinite symlink loop during project discovery",
-	)
-	require.Nil(t, err)
+	assert.Panics(t, func() { FindProjects() }, "Infinite symlink loop encountered during project discovery")
 }
 
 func TestFindProjects(t *testing.T) {