os/exec: add Cmd.String

The initial implementation is intentionally simple.
Let's see how far it gets us.

Fixes #30638

Change-Id: I240afae2b401744ab2ff2a69952c4eb0fd3feb56
Reviewed-on: https://go-review.googlesource.com/c/go/+/168518
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/src/os/exec/exec_test.go b/src/os/exec/exec_test.go
index 3e6b7bb95e..26be62dd92 100644
--- a/src/os/exec/exec_test.go
+++ b/src/os/exec/exec_test.go
@@ -1150,3 +1150,37 @@ func TestDedupEnvEcho(t *testing.T) {
 		t.Errorf("output = %q; want %q", got, want)
 	}
 }
+
+func TestString(t *testing.T) {
+	echoPath, err := exec.LookPath("echo")
+	if err != nil {
+		t.Skip(err)
+	}
+	tests := [...]struct {
+		path string
+		args []string
+		want string
+	}{
+		{"echo", nil, echoPath},
+		{"echo", []string{"a"}, echoPath + " a"},
+		{"echo", []string{"a", "b"}, echoPath + " a b"},
+	}
+	for _, test := range tests {
+		cmd := exec.Command(test.path, test.args...)
+		if got := cmd.String(); got != test.want {
+			t.Errorf("String(%q, %q) = %q, want %q", test.path, test.args, got, test.want)
+		}
+	}
+}
+
+func TestStringPathNotResolved(t *testing.T) {
+	_, err := exec.LookPath("makemeasandwich")
+	if err == nil {
+		t.Skip("wow, thanks")
+	}
+	cmd := exec.Command("makemeasandwich", "-lettuce")
+	want := "makemeasandwich -lettuce"
+	if got := cmd.String(); got != want {
+		t.Errorf("String(%q, %q) = %q, want %q", "makemeasandwich", "-lettuce", got, want)
+	}
+}