Respect `ANDROID_SERIAL` environment variable used by ADB

[ldrumm]

Summary

Respect ANDROID_SERIAL environment variable used by ADB

When multiple Android devices are attached, the default behaviour of ADB
is to resolve a device number based on the presence of ANDROID_SERIAL if
the serial number is not explicitly passed by the -s parameter. This patch
emulates that behaviour in lldb's ADB platform connector

[ovyalov]

source/Plugins/Platform/Android/AdbClient.cpp

115

Could you check whether serial number coming from ANDROID_SERIAL is within connect_devices?

[ldrumm]

• Ensure if ANDROID_SERIAL is set, it exists in the list of connected devices (Address feedback from @ovyalov)
• Also add a hint in the error message in case multiple devices are attached and no serial number is available.

[ovyalov]

LGTM

source/Plugins/Platform/Android/AdbClient.cpp

 #include "lldb/Core/DataEncoder.h"
 #include "lldb/Core/DataExtractor.h"
 #include "lldb/Core/StreamString.h"
 #include "lldb/Host/ConnectionFileDescriptor.h"
 #include "lldb/Host/FileSpec.h"
 
 #include <limits.h>
 
+#include <cstdlib>
 #include <algorithm>
 #include <fstream>
 #include <sstream>
 
 // On Windows, transitive dependencies pull in <Windows.h>, which defines a
 // macro that clashes with a method name.
 #ifdef SendMessage
 #undef SendMessage

 Error
 AdbClient::CreateByDeviceID(const std::string &device_id, AdbClient &adb)
 {
     DeviceIDList connect_devices;
     auto error = adb.GetDevices(connect_devices);
     if (error.Fail())
         return error;
 
-    if (device_id.empty())
+    std::string android_serial;
+    if (!device_id.empty())
+        android_serial = device_id;
+    else if (const char *env_serial = std::getenv("ANDROID_SERIAL"))
+        android_serial = env_serial;
+
+    if (android_serial.empty())
     {
         if (connect_devices.size() != 1)
-            return Error("Expected a single connected device, got instead %" PRIu64,
-                    static_cast<uint64_t>(connect_devices.size()));
-
+            return Error("Expected a single connected device, got instead %zu - try setting 'ANDROID_SERIAL'",
+                         connect_devices.size());
         adb.SetDeviceID(connect_devices.front());
     }
     else
     {
-        auto find_it = std::find(connect_devices.begin(), connect_devices.end(), device_id);
+        auto find_it = std::find(connect_devices.begin(), connect_devices.end(), android_serial);
         if (find_it == connect_devices.end())
-            return Error("Device \"%s\" not found", device_id.c_str());
+            return Error("Device \"%s\" not found", android_serial.c_str());
 
         adb.SetDeviceID(*find_it);
     }
     return error;
 }
 
 AdbClient::AdbClient () {}