service/debugger: Assume current dir for exec (go-delve#3167)

This patch modifies the behavior of the exec subcommand such that
you don't necessarily have to write the "./" prefix when trying
to debug a precompiled binary in your working directory.

For example (given foo.test in working dir), before this change:

dlv exec foo.test

Would result in an error, forcing the user to type:

dlv exec ./foo.test

This just makes things a bit more convenient.

pkg/proc/native/proc_windows.go

@@ -3,7 +3,6 @@ package native
 import (
 	"fmt"
 	"os"
-	"path/filepath"
 	"syscall"
 	"unsafe"
 
@@ -25,10 +24,7 @@ func (os *osProcessDetails) Close() {}
 
 // Launch creates and begins debugging a new process.
 func Launch(cmd []string, wd string, flags proc.LaunchFlags, _ []string, _ string, redirects [3]string) (*proc.Target, error) {
-	argv0Go, err := filepath.Abs(cmd[0])
-	if err != nil {
-		return nil, err
-	}
+	argv0Go := cmd[0]
 
 	env := proc.DisableAsyncPreemptEnv()
 

service/debugger/debugger.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"go/parser"
 	"go/token"
+	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -246,9 +247,11 @@ func (d *Debugger) TargetGoVersion() string {
 
 // Launch will start a process with the given args and working directory.
 func (d *Debugger) Launch(processArgs []string, wd string) (*proc.Target, error) {
-	if err := verifyBinaryFormat(processArgs[0]); err != nil {
+	fullpath, err := verifyBinaryFormat(processArgs[0])
+	if err != nil {
 		return nil, err
 	}
+	processArgs[0] = fullpath
 
 	launchFlags := proc.LaunchFlags(0)
 	if d.config.Foreground {
@@ -2259,34 +2262,31 @@ func noDebugErrorWarning(err error) error {
 	return err
 }
 
-func verifyBinaryFormat(exePath string) error {
-	f, err := os.Open(exePath)
+func verifyBinaryFormat(exePath string) (string, error) {
+	fullpath, err := filepath.Abs(exePath)
 	if err != nil {
-		return err
+		return "", err
+	}
+
+	f, err := os.Open(fullpath)
+	if err != nil {
+		return "", err
 	}
 	defer f.Close()
 
-	switch runtime.GOOS {
-	case "windows":
-		// Make sure the binary exists and is an executable file
-		if filepath.Base(exePath) == exePath {
-			if _, err := exec.LookPath(exePath); err != nil {
-				return err
-			}
-		}
-	default:
-		fi, err := f.Stat()
+	// Skip this check on Windows.
+	// TODO(derekparker) exec.LookPath looks for valid Windows extensions.
+	// We don't create our binaries with valid extensions, even though we should.
+	// Skip this check for now.
+	if runtime.GOOS != "windows" {
+		_, err = exec.LookPath(fullpath)
 		if err != nil {
-			return err
-		}
-		if (fi.Mode() & 0111) == 0 {
-			return api.ErrNotExecutable
+			return "", api.ErrNotExecutable
 		}
 	}
 
 	// check that the binary format is what we expect for the host system
-	var exe interface{ Close() error }
-
+	var exe io.Closer
 	switch runtime.GOOS {
 	case "darwin":
 		exe, err = macho.NewFile(f)
@@ -2299,10 +2299,10 @@ func verifyBinaryFormat(exePath string) error {
 	}
 
 	if err != nil {
-		return api.ErrNotExecutable
+		return "", api.ErrNotExecutable
 	}
 	exe.Close()
-	return nil
+	return fullpath, nil
 }
 
 var attachErrorMessage = attachErrorMessageDefault

service/debugger/debugger_test.go

@@ -5,6 +5,7 @@ import (
 	"os"
 	"path/filepath"
 	"runtime"
+	"strings"
 	"testing"
 
 	"github.com/go-delve/delve/pkg/gobuild"
@@ -68,3 +69,35 @@ func TestDebugger_LaunchInvalidFormat(t *testing.T) {
 		t.Fatalf("expected error \"%s\" got \"%v\"", api.ErrNotExecutable, err)
 	}
 }
+
+func TestDebugger_LaunchCurrentDir(t *testing.T) {
+	fixturesDir := protest.FindFixturesDir()
+	testDir := filepath.Join(fixturesDir, "buildtest")
+	debugname := "debug"
+	exepath := filepath.Join(testDir, debugname)
+	originalPath, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(originalPath)
+	defer func() {
+		if err := os.Remove(exepath); err != nil {
+			t.Fatalf("error removing executable %v", err)
+		}
+	}()
+	if err := gobuild.GoBuild(debugname, []string{testDir}, fmt.Sprintf("-o %s", exepath)); err != nil {
+		t.Fatalf("go build error %v", err)
+	}
+
+	os.Chdir(testDir)
+
+	d := new(Debugger)
+	d.config = &Config{}
+	_, err = d.Launch([]string{debugname}, ".")
+	if err == nil {
+		t.Fatal("expected error but none was generated")
+	}
+	if err != nil && !strings.Contains(err.Error(), "unknown backend") {
+		t.Fatal(err)
+	}
+}