The error output from the compilation is not always in the json output of the compile command

[Renaud11232]

Bug Report

Current behavior

When compiling a sketch with missing libraries using the --format json flag, the error output is on stderr instead of being in the json output.

Test.ino :

#include "Dummy.h"

void setup() {
}

void loop() {
}

Compiling with the following command :

.\arduino-cli_0.18.0_Windows_64bit\arduino-cli.exe compile --format json --fqbn arduino:avr:mega:cpu=atmega2560 Test

Gives the following output :

stdout

{
  "compiler_out": "",
  "compiler_err": "",
  "builder_result": {
    "build_path": "C:\\Users\\gaspa\\AppData\\Local\\Temp\\arduino-sketch-2422F2901866CFBFF08F6C5D307E5DE3"
  },
  "success": false
}

stderr

C:\Users\gaspa\Downloads\Test\Test.ino:1:10: fatal error: Dummy.h: No such file or directory
 #include "Dummy.h"
          ^~~~~~~~~
compilation terminated.

Expected behavior

The error output should be printed on stdout in the json ouput
i.e:

{
  "compiler_out": "",
  "compiler_err": "C:\\Users\\gaspa\\Downloads\\Test\\Test.ino:1:10: fatal error: Dummy.h: No such file or directory\r\n#include \"Dummy.h\"\r\n          ^~~~~~~~~\r\ncompilation terminated.",
  "builder_result": {
    "build_path": "C:\\Users\\gaspa\\AppData\\Local\\Temp\\arduino-sketch-2422F2901866CFBFF08F6C5D307E5DE3"
  },
  "success": false
}

Environment

• CLI version : arduino-cli.exe alpha Version: 0.18.0 Commit: 46c23166 Date: 2021-03-31T09:42:54Z
• OS and platform: Windows 64bit as well as Linux ARMv6

Additional context

This might be caused by #174

Thanks

[per1234]

I'm happy to report that this bug no longer occurs. I am able to reproduce it with Arduino CLI 0.18.0, but not with the latest build (I believe it was fixed by #1523):

$ ./arduino-cli version
arduino-cli.exe  Version: nightly-20220325 Commit: b86e5cf Date: 2022-03-25T01:33:19Z

$ ./arduino-cli.exe compile --format json --fqbn arduino:avr:mega:cpu=atmega2560 Test
{
  "compiler_out": "",
  "compiler_err": "E:\\arduino\\cli\\arduino-cli_nightly\\Test\\Test.ino:1:10: fatal error: Dummy.h: No such file or directory\r\n #include \"Dummy.h\"\r\n          ^~~~~~~~~\r\ncompilation terminated.\r\n\n",
  "builder_result": {
    "build_path": "C:\\Users\\per\\AppData\\Local\\Temp\\arduino-sketch-42DD0DDDB74BE3523412ACA473F339F0",
    "board_platform": {
      "id": "arduino:avr",
      "version": "1.8.5"
    },
    "build_platform": {
      "id": "arduino:avr",
      "version": "1.8.5"
    }
  },
  "success": false
}
Error during build: exit status 1

There is still that "Error during build: exit status 1", but this is an error message from Arduino CLI rather than the compiler, so I don't think it really belongs in the compiler_err field. It is printed to stderr, so should not pose any problems for machine parsing of the JSON output from stdout.