fix: use ActiveDirectoryDefault for -G with no username (#754)

Author: dlevy-msft-sql

cmd/sqlcmd/sqlcmd.go

@@ -207,7 +207,8 @@ func (a SQLCmdArguments) authenticationMethod(hasPassword bool) string {
 	if a.UseAad {
 		switch {
 		case a.UserName == "":
-			return azuread.ActiveDirectoryIntegrated
+			// Default walks the Azure credential chain; works in non-interactive shells (issue #699).
+			return azuread.ActiveDirectoryDefault
 		case hasPassword:
 			return azuread.ActiveDirectoryPassword
 		default:

cmd/sqlcmd/sqlcmd_test.go

@@ -525,6 +525,26 @@ func TestConditionsForPasswordPrompt(t *testing.T) {
 	}
 }
 
+func TestAuthenticationMethodForUseAad(t *testing.T) {
+	tests := []struct {
+		name        string
+		userName    string
+		hasPassword bool
+		expected    string
+	}{
+		{"-G no username picks Default", "", false, azuread.ActiveDirectoryDefault},
+		{"-G no username, password ignored", "", true, azuread.ActiveDirectoryDefault},
+		{"-G with username, no password picks Interactive", "user@contoso", false, azuread.ActiveDirectoryInteractive},
+		{"-G with username and password picks Password", "user@contoso", true, azuread.ActiveDirectoryPassword},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			a := SQLCmdArguments{UseAad: true, UserName: tc.userName}
+			assert.Equal(t, tc.expected, a.authenticationMethod(tc.hasPassword))
+		})
+	}
+}
+
 func TestStartupScript(t *testing.T) {
 	o, err := os.CreateTemp("", "sqlcmdmain")
 	assert.NoError(t, err, "os.CreateTemp")