Handle package import paths that are in subfolders of Go module path

cmd/xcaddy/main.go

@@ -21,6 +21,7 @@ import (
 	"os"
 	"os/exec"
 	"os/signal"
+	"path"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -192,11 +193,20 @@ func runDev(ctx context.Context, args []string) error {
 		})
 	}
 
+	// reconcile remaining path segments; for example if a module foo/a
+	// is rooted at directory path /home/foo/a, but the current directory
+	// is /home/foo/a/b, then the package to import should be foo/a/b
+	cwd, err := os.Getwd()
+	if err != nil {
+		return fmt.Errorf("unable to determine current directory: %v", err)
+	}
+	importPath := path.Join(currentModule, strings.TrimPrefix(cwd, filepath.ToSlash(moduleDir)))
+
 	// build caddy with this module plugged in
 	builder := xcaddy.Builder{
 		CaddyVersion: caddyVersion,
 		Plugins: []xcaddy.Dependency{
-			{ModulePath: currentModule},
+			{ModulePath: importPath},
 		},
 		Replacements: replacements,
 		RaceDetector: raceDetector,

environment.go

@@ -131,10 +131,16 @@ func (b Builder) newEnvironment(ctx context.Context) (*environment, error) {
 	if err != nil {
 		return nil, err
 	}
+nextPlugin:
 	for _, p := range b.Plugins {
-		// if module is locally available; do not "go get" it
-		if replaced[p.ModulePath] != "" {
-			continue
+		// if module is locally available, do not "go get" it;
+		// also note that we iterate and check prefixes, because
+		// a plugin package may be a subfolder of a module, i.e.
+		// foo/a/plugin is within module foo/a.
+		for repl := range replaced {
+			if strings.HasPrefix(p.ModulePath, repl) {
+				continue nextPlugin
+			}
 		}
 		err = env.execGoGet(ctx, p.ModulePath, p.Version)
 		if err != nil {