diff --git a/src/Makefile.am b/src/Makefile.am
index d2e32e2c8..7d60d7e9d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -65,6 +65,7 @@ endif
 PRETTY_SUBDIRS                          = \
     cli                                   \
     core                                  \
+    diag                                  \
     ncp                                   \
     posix                                 \
     $(NULL)
diff --git a/src/diag/diag_process.cpp b/src/diag/diag_process.cpp
index 4fe5af068..5ca2893f7 100644
--- a/src/diag/diag_process.cpp
+++ b/src/diag/diag_process.cpp
@@ -44,39 +44,33 @@
 namespace ot {
 namespace Diagnostics {
 
-const struct Diag::Command Diag::sCommands[] =
-{
-    { "start", &ProcessStart },
-    { "stop", &ProcessStop },
-    { "channel", &ProcessChannel },
-    { "power", &ProcessPower },
-    { "send", &ProcessSend },
-    { "repeat", &ProcessRepeat },
-    { "stats", &ProcessStats },
-    { NULL, NULL },
+const struct Diag::Command Diag::sCommands[] = {
+    {"start", &ProcessStart}, {"stop", &ProcessStop},     {"channel", &ProcessChannel}, {"power", &ProcessPower},
+    {"send", &ProcessSend},   {"repeat", &ProcessRepeat}, {"stats", &ProcessStats},     {NULL, NULL},
 };
 
 struct Diag::DiagStats Diag::sStats;
 
-int8_t Diag::sTxPower;
-uint8_t Diag::sChannel;
-uint8_t Diag::sTxLen;
-uint32_t Diag::sTxPeriod;
-uint32_t Diag::sTxPackets;
-otRadioFrame * Diag::sTxPacket;
-bool Diag::sRepeatActive;
-otInstance *Diag::sInstance;
+int8_t        Diag::sTxPower;
+uint8_t       Diag::sChannel;
+uint8_t       Diag::sTxLen;
+uint32_t      Diag::sTxPeriod;
+uint32_t      Diag::sTxPackets;
+otRadioFrame *Diag::sTxPacket;
+bool          Diag::sRepeatActive;
+otInstance *  Diag::sInstance;
 
 void Diag::Init(otInstance *aInstance)
 {
-    sInstance = aInstance;
-    sChannel = 20;
-    sTxPower = 0;
-    sTxPeriod = 0;
-    sTxLen = 0;
-    sTxPackets = 0;
+    sInstance     = aInstance;
+    sChannel      = 20;
+    sTxPower      = 0;
+    sTxPeriod     = 0;
+    sTxLen        = 0;
+    sTxPackets    = 0;
     sRepeatActive = false;
     memset(&sStats, 0, sizeof(struct DiagStats));
+
     sTxPacket = otPlatRadioGetTransmitBuffer(sInstance);
     otPlatDiagChannelSet(sChannel);
     otPlatDiagTxPowerSet(sTxPower);
@@ -170,7 +164,7 @@ otError Diag::ParseLong(char *aArgVector, long &aValue)
 
 void Diag::TxPacket(void)
 {
-    sTxPacket->mLength = sTxLen;
+    sTxPacket->mLength  = sTxLen;
     sTxPacket->mChannel = sChannel;
 
     for (uint8_t i = 0; i < sTxLen; i++)
@@ -185,7 +179,6 @@ void Diag::ProcessChannel(int aArgCount, char *aArgVector[], char *aOutput, size
 {
     otError error = OT_ERROR_NONE;
 
-
     VerifyOrExit(otPlatDiagModeGet(), error = OT_ERROR_INVALID_STATE);
 
     if (aArgCount == 0)
@@ -239,7 +232,7 @@ exit:
 void Diag::ProcessSend(int aArgCount, char *aArgVector[], char *aOutput, size_t aOutputMaxLen)
 {
     otError error = OT_ERROR_NONE;
-    long value;
+    long    value;
 
     VerifyOrExit(otPlatDiagModeGet(), error = OT_ERROR_INVALID_STATE);
     VerifyOrExit(aArgCount == 2, error = OT_ERROR_INVALID_ARGS);
@@ -286,7 +279,7 @@ void Diag::ProcessRepeat(int aArgCount, char *aArgVector[], char *aOutput, size_
         sTxLen = static_cast<uint8_t>(value);
 
         sRepeatActive = true;
-        uint32_t now = otPlatAlarmMilliGetNow();
+        uint32_t now  = otPlatAlarmMilliGetNow();
         otPlatAlarmMilliStartAt(sInstance, now, sTxPeriod);
         snprintf(aOutput, aOutputMaxLen, "sending packets of length %#x at the delay of %#x ms\r\nstatus 0x%02x\r\n",
                  static_cast<int>(sTxLen), static_cast<int>(sTxPeriod), error);
@@ -307,8 +300,8 @@ void Diag::ProcessStats(int aArgCount, char *aArgVector[], char *aOutput, size_t
 
     snprintf(aOutput, aOutputMaxLen,
              "received packets: %d\r\nsent packets: %d\r\nfirst received packet: rssi=%d, lqi=%d\r\n",
-            static_cast<int>(sStats.mReceivedPackets), static_cast<int>(sStats.mSentPackets),
-            static_cast<int>(sStats.mFirstRssi), static_cast<int>(sStats.mFirstLqi));
+             static_cast<int>(sStats.mReceivedPackets), static_cast<int>(sStats.mSentPackets),
+             static_cast<int>(sStats.mFirstRssi), static_cast<int>(sStats.mFirstLqi));
 
 exit:
     AppendErrorResult(error, aOutput, aOutputMaxLen);
@@ -347,7 +340,7 @@ void Diag::DiagReceiveDone(otInstance *aInstance, otRadioFrame *aFrame, otError
         if (sStats.mReceivedPackets == 0)
         {
             sStats.mFirstRssi = aFrame->mInfo.mRxInfo.mRssi;
-            sStats.mFirstLqi = aFrame->mInfo.mRxInfo.mLqi;
+            sStats.mFirstLqi  = aFrame->mInfo.mRxInfo.mLqi;
         }
 
         sStats.mReceivedPackets++;
@@ -362,7 +355,7 @@ void Diag::AlarmFired(otInstance *aInstance)
 {
     VerifyOrExit(aInstance == sInstance);
 
-    if(sRepeatActive)
+    if (sRepeatActive)
     {
         uint32_t now = otPlatAlarmMilliGetNow();
 
@@ -395,5 +388,5 @@ extern "C" void otPlatDiagRadioReceiveDone(otInstance *aInstance, otRadioFrame *
     Diag::DiagReceiveDone(aInstance, aFrame, aError);
 }
 
-}  // namespace Diagnostics
-}  // namespace ot
+} // namespace Diagnostics
+} // namespace ot
diff --git a/src/diag/diag_process.hpp b/src/diag/diag_process.hpp
index 8f44bd1dd..bca053f77 100644
--- a/src/diag/diag_process.hpp
+++ b/src/diag/diag_process.hpp
@@ -81,21 +81,23 @@ private:
     static void ProcessChannel(int aArgCount, char *aArgVector[], char *aOutput, size_t aOutputMaxLen);
     static void ProcessPower(int aArgCount, char *aArgVector[], char *aOutput, size_t aOutputMaxLen);
     static void TxPacket(void);
+
     static otError ParseLong(char *aString, long &aLong);
 
     static const struct Command sCommands[];
-    static struct DiagStats sStats;
-    static int8_t sTxPower;
-    static uint8_t sChannel;
-    static uint8_t sTxLen;
-    static uint32_t sTxPeriod;
-    static uint32_t sTxPackets;
+    static struct DiagStats     sStats;
+
+    static int8_t        sTxPower;
+    static uint8_t       sChannel;
+    static uint8_t       sTxLen;
+    static uint32_t      sTxPeriod;
+    static uint32_t      sTxPackets;
     static otRadioFrame *sTxPacket;
-    static otInstance *sInstance;
-    static bool sRepeatActive;
+    static otInstance *  sInstance;
+    static bool          sRepeatActive;
 };
 
-}  // namespace Diagnostics
-}  // namespace ot
+} // namespace Diagnostics
+} // namespace ot
 
-#endif  // CLI_HPP_
+#endif // CLI_HPP_
diff --git a/src/diag/openthread-diag.cpp b/src/diag/openthread-diag.cpp
index 762054731..d4f973d84 100644
--- a/src/diag/openthread-diag.cpp
+++ b/src/diag/openthread-diag.cpp
@@ -59,13 +59,13 @@ void otDiagProcessCmdLine(const char *aInput, char *aOutput, size_t aOutputMaxLe
 {
     enum
     {
-        kMaxArgs = OPENTHREAD_CONFIG_DIAG_CMD_LINE_ARGS_MAX,
+        kMaxArgs          = OPENTHREAD_CONFIG_DIAG_CMD_LINE_ARGS_MAX,
         kMaxCommandBuffer = OPENTHREAD_CONFIG_DIAG_CMD_LINE_BUFFER_SIZE,
     };
 
     otError error = OT_ERROR_NONE;
-    char buffer[kMaxCommandBuffer];
-    char *argVector[kMaxArgs];
+    char    buffer[kMaxCommandBuffer];
+    char *  argVector[kMaxArgs];
     uint8_t argCount = 0;
 
     VerifyOrExit(strnlen(aInput, kMaxCommandBuffer) < kMaxCommandBuffer, error = OT_ERROR_NO_BUFS);