Update telnet_cli.h to take into account DISABLE_CLI_TELNET

[antongorodezkiy]

Description

Added telnet functions placeholders for cases when DISABLE_CLI_TELNET=1

Related Issues

Tests

[antongorodezkiy]

Hello @hpsaturn, thank you for your package 👍

I used hpsaturn/ESP32 Wifi CLI@^0.3.3 for a while in my pet project and on some stage of developing the RAM overflowed.
Started to debug here and there, looked into PlatformIO Inspect tool and found that the <ESP32WifiCLI.hpp/telnet_cli.h> takes 24Kb though I don't actually use any telnet functions and don't plan to.

I looked through the library code and found DISABLE_CLI_TELNET constant. Pretty straightforward - so I turned it off in the platformio.ini:

...
build_flags =
	...
	-D SHELLMINATOR_BUFF_LEN=128
	-D SHELLMINATOR_BUFF_DIM=128
	-D COMMANDER_MAX_COMMAND_SIZE=128
	-D WCLI_MAX_CMDS=14
    -D DISABLE_CLI_TELNET=1
...

And after that the project stopped to compile because it expected for those functions:

~/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: .pio/build/ttgo-lora32-v1/lib18e/libESP32 Wifi CLI.a(ESP32WifiCLI.cpp.o):(.literal._Z9_nmcli_upPcP6Stream+0x4): undefined reference to `ESP32WifiCLI::isTelnetEnable()'
~/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: .pio/build/ttgo-lora32-v1/lib18e/libESP32 Wifi CLI.a(ESP32WifiCLI.cpp.o):(.literal._Z9_nmcli_upPcP6Stream+0x8): undefined reference to `ESP32WifiCLI::isTelnetRunning()'
~/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: .pio/build/ttgo-lora32-v1/lib18e/libESP32 Wifi CLI.a(ESP32WifiCLI.cpp.o):(.literal._Z9_nmcli_upPcP6Stream+0xc): undefined reference to `ESP32WifiCLI::enableTelnet()'
~/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: .pio/build/ttgo-lora32-v1/lib18e/libESP32 Wifi CLI.a(ESP32WifiCLI.cpp.o): in function `_nmcli_up(char*, Stream*)':
~/programming/embedded/SmartPosition/Monitor/.pio/libdeps/ttgo-lora32-v1/ESP32 Wifi CLI/src/ESP32WifiCLI.cpp:372: undefined reference to `ESP32WifiCLI::isTelnetEnable()'
~/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: ~/programming/embedded/SmartPosition/Monitor/.pio/libdeps/ttgo-lora32-v1/ESP32 Wifi CLI/src/ESP32WifiCLI.cpp:372: undefined reference to `ESP32WifiCLI::isTelnetRunning()'
~/.platformio/packages/toolchain-xtensa-esp32/bin/../lib/gcc/xtensa-esp32-elf/8.4.0/../../../../xtensa-esp32-elf/bin/ld: ~/programming/embedded/SmartPosition/Monitor/.pio/libdeps/ttgo-lora32-v1/ESP32 Wifi CLI/src/ESP32WifiCLI.cpp:372: undefined reference to `ESP32WifiCLI::enableTelnet()'

The ugly workaround I used is to include the following file in my main.cpp:

#include <ESP32WifiCLI.hpp>

#ifdef DISABLE_CLI_TELNET
void ESP32WifiCLI::enableTelnet() {
}

void ESP32WifiCLI::disableTelnet() {
}

bool ESP32WifiCLI::isTelnetEnable() {
    return false;
}

bool ESP32WifiCLI::isTelnetRunning() {
    return false;
}
#endif

Th project compiled and the memory issue is gone so far.

[hpsaturn]

Thanks for your contribution. It's true, the Telnet feature consume more memory. Thanks to notice the missing prototypes for this case.