Error: unable to locate `compile_commands.json`

[avsteele]

Description

If you set the output path to something inside the project folder I get errors when trying to verify the sketch.

The error looks like

[Starting] Verifying sketch 'testing_error.ino'
Please see the build logs in output path: c:\Users\avste\source\Arduino\testing_error\.out
Error during build: unable to read contents of the source item: open C:\Users\avste\source\Arduino\testing_error\.out\compile_commands.json: The system cannot find the file specified.
[Warning] Failed to generate IntelliSense configuration.
[Error] Verifying sketch 'testing_error.ino': Exit with code=1

• The first time you verify, or if you delete the existing output folder, it does not give this error.
• Occasionally (maybe 1/5 times) it will build without this error
• If the output folder is where outside the project folder (e.g. c:\temp\) you will not get this error (ever as far as I've seen)
• After you get the error the compile_command.json file will be empty except for a []

Steps to replicate

Make a new project. Board= Uno, programmer = AVR ISP

sketch file

#include <Arduino.h>
void setup(){}
void loop(){}

arduino.json

{
    "board": "arduino:avr:uno",
    "programmer": "avrisp",
    "sketch": "testing_error.ino",
    "output":".out"
}

in arduino.json set the output folder to something relative (.e.g .out). Compile once (will complete ok. If you try it again, you will get the error (~80% of the time). If you get the output folder somewhere else you do not get the error.

[GregTerrell]

Also seeing this. If the "empty" compile_commands.json file is deleted the build succeeds.

I have relied on the .build folder (located as a sibling to the .vscode folder in the project) to speed builds. If you are working with a large number of sketch folders it is difficult to have unique locations for the build output outside of the project folder.

Possibly allowing a ${} variable inside the arduino.json output parameter would be an alternative. Like example below...

{ "sketch": "LTEmC-5-modeminfo.ino", "configuration": "opt=small,usbstack=arduino,debug=on", "board": "adafruit:samd:adafruit_feather_m0_express", "output": "../build/${workspace}" }

[mikalhart]

I'm seeing this as well, and concur with @GregTerrell that deleting the (almost) empty compile_command.json file makes the build succeed (but then you get a full rebuild and you've lost all the advantage of having "output" in arduino.json).

FWIW, my "output" folder is currently "./.output".

[37electrons]

I found this discussion since I was seeing exactly the same issue. My setting in 'arduino.json' was "output": ".//.build"

After it was changed to "output": "./build" everything started working every single time.

Not sure what the root cause of the problem was though. Perhaps the directory name starting with a dot. I am on Win10, fwiw.

[GregTerrell]

Concur with @37electrons. The behavior seems tied to the . prefix on the build directory if it is in the project directory. If the .build is in the parent directory, seems to work ok.

I have been using .build to follow the .vscode convention and simplify my gitignore rules.

[avsteele]

The error persists if the output directory in a subfolder, even if it does not start with a dot, if the name of the folder contains the word out (at least).

These all result in the error

"output": "out"
"output": "output"
"output": "outzz"
"output": "zzout"
"output": ".output"
"output": ".//.output"
"output": ".build"
"output": ".//.build"

These do not

"output": "build"
"output": "./build"