adding the path WHERE the compiler was searching for a include-file

[StefanL38]

Please read the Issues section of the Contributing Rules at the "Contributing" link to the right before submitting an issue report.
Hello Everybody,

You should add the path where the compiler was searching for an include-file to make it easy for users to find the real cause of an error "No such file or directory"

I wrote the explaining text here:
https://forum.arduino.cc/t/extending-compiler-error-message-no-such-file-or-directory-for-better-guiding-to-the-real-reason/916278

here is additional information
https://forum.arduino.cc/t/how-can-a-library-properties-file-cause-an-error-no-such-file-or-directory/916101

and this documents the pain I had to find the real reason starting at post #15
https://forum.arduino.cc/t/evolved-library-keyboard-emulator-for-german-keyboard-layout-old-title-printing-characters-that-have-a-multibyte-representation-to-a-keyboard-emulator-does-not-work-like-write/914779

best regards Stefan

[per1234]

Hi @StefanL38. Thanks for your suggestion. The problem is that there are many paths the library discovery system and compiler search for these files. The very nature of the error is such that there is no way to identify a single one of those locations to use in the error message. If they were all added to the error message it would become an unapproachable wall of cryptic text.

If you turn on the verbose output during compilation, you can get a general idea of the include search paths. Here you can see that even just the high level parent paths passed to arduino-builder via the -hardware, -tools, -built-in-libraries, -libraries, and -build-path flags are already a lot:

C:\program-files\arduino\ide\arduino-1.8.16\arduino-builder -dump-prefs -logger=machine -hardware C:\program-files\arduino\ide\arduino-1.8.16\hardware -hardware C:\Users\per\AppData\Local\Arduino15\packages -tools C:\program-files\arduino\ide\arduino-1.8.16\tools-builder -tools C:\program-files\arduino\ide\arduino-1.8.16\hardware\tools\avr -tools C:\Users\per\AppData\Local\Arduino15\packages -built-in-libraries C:\program-files\arduino\ide\arduino-1.8.16\libraries -libraries E:\deleteme\asdf\Arduino\libraries -fqbn=arduino:avr:uno -ide-version=10816 -build-path C:\Users\per\AppData\Local\Temp\arduino_build_322235 -warnings=all -build-cache C:\Users\per\AppData\Local\Temp\arduino_cache_634742 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.avrdude.path=C:\Users\per\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17 -prefs=runtime.tools.avrdude-6.3.0-arduino17.path=C:\Users\per\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17 -prefs=runtime.tools.avr-gcc.path=C:\Users\per\AppData\Local\Arduino15\packages\arduino\tools\avr-gcc\7.3.0-atmel3.6.1-arduino7 -prefs=runtime.tools.avr-gcc-7.3.0-atmel3.6.1-arduino7.path=C:\Users\per\AppData\Local\Arduino15\packages\arduino\tools\avr-gcc\7.3.0-atmel3.6.1-arduino7 -prefs=runtime.tools.arduinoOTA.path=C:\Users\per\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.3.0 -prefs=runtime.tools.arduinoOTA-1.3.0.path=C:\Users\per\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.3.0 -verbose C:\Users\per\AppData\Local\Temp\arduino_modified_sketch_311573\sketch_oct19a.ino

You also have the paths passed to the compiler via -I flags in the compilation commands:

"C:\\Users\\per\\AppData\\Local\\Arduino15\\packages\\arduino\\tools\\avr-gcc\\7.3.0-atmel3.6.1-arduino7/bin/avr-g++" -c -g -Os -w -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -Wno-error=narrowing -flto -w -x c++ -E -CC -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10816 -DARDUINO_AVR_UNO -DARDUINO_ARCH_AVR "-IC:\\Users\\per\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.3\\cores\\arduino" "-IC:\\Users\\per\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.3\\variants\\standard" "-IC:\\program-files\\arduino\\ide\\arduino-1.8.16\\libraries\\Servo\\src" "C:\\Users\\per\\AppData\\Local\\Temp\\arduino_build_322235\\sketch\\sketch_oct19a.ino.cpp" -o nul

but the library paths in those flags are the ones where a library was discovered, so you won't see all the paths where a library was not discovered.

So unfortunately I think it's not feasible to implement that.