Sketches with `#include Math.h` do not compile via GH Action (but do locally)

[aliphys]

Describe the problem

If a sketch has #include "Math.h", the arduino/compile-sketches GitHub Action will return fatal error: Math.h: No such file or directory. However, the same sketch compiles and executes locally as expected.

  /home/runner/work/nicla-sense-me-fw/nicla-sense-me-fw/Arduino_BHY2/examples/Magnetometer/Magnetometer.ino:17:10: fatal error: Math.h: No such file or directory
   #include "Math.h"
            ^~~~~~~~
  compilation terminated.
  
  Used library Version Path
  Arduino_BHY2 1.0.6   /home/runner/work/nicla-sense-me-fw/nicla-sense-me-fw/Arduino_BHY2
  ArduinoBLE   1.3.6   /home/runner/Arduino/libraries/ArduinoBLE
  
  Used platform      Version Path
  arduino:mbed_nicla 4.1.3   /home/runner/.arduino15/packages/arduino/hardware/mbed_nicla/4.1.3
  Error during build: exit status 1

To reproduce

1. Compile the sketch below for the Nicla Sense ME locally. It should compile, and magnetometer data is received over the Serial connection

/*
 * This example shows how to use the access the magnetometer data and send it over serial.
 * 
 * Every 1 second, this sketch will send the heading of the magnetometer over serial.
 * by calculating the arctangent between the x and y axis and multiplied in a conversion
 * factor to convert the headings from radians to degrees.
 * 
 * Instructions:
 * 1. Upload this sketch to your Nicla Sense ME board.
 * 2. Open the Serial Monitor at a baud rate of 115200.
 * 3. The heading of the magnetometer will be printed to the serial monitor.
 * 
 * Initial author: @mcmchris
 */

#include "Arduino_BHY2.h"
#include "Math.h"

SensorXYZ magnetometer(SENSOR_ID_MAG);

float heading = 0;
unsigned long previousMillis = 0;  // will store last time the sensor was updated
const long interval = 1000;

void setup() {
  Serial.begin(115200);
  BHY2.begin();
  magnetometer.begin();
}

void loop() {
  BHY2.update();
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    heading = round(atan2(magnetometer.x(), magnetometer.y()) * 180.0 / PI);
    Serial.println(String(heading) + "º");
  }
}

2. Run this GitHub Workflow, which includes this section

      - name: Compile examples
        uses: arduino/compile-sketches@v1
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          fqbn: ${{ matrix.board.fqbn }}
          platforms: ${{ matrix.board.platforms }}
          libraries: |
            # Board-specific libraries
            ${{ matrix.bhy2-libraries }}
            ${{ matrix.bhy2host-libraries }}
            ${{ matrix.board.libraries }}
            ${{ matrix.arduinoiotcloud-libraries }}
            ${{ matrix.blebridge-libraries }}
          sketch-paths: |
            ${{ matrix.bhy2-sketch-paths }}
            ${{ matrix.bhy2host-sketch-paths }}
            ${{ matrix.arduinoiotcloud-sketch-paths }}
            ${{ matrix.blebridge-sketch-paths }}
          enable-deltas-report: true
          sketches-report-path: ${{ env.SKETCHES_REPORTS_PATH }}

3. The error regarding Math.h is displayed here

Expected behavior

If a sketch is able to compile locally and Math.h is found, then I also expect the CLI to do the same and not give an error.

'arduino/compile-sketches' version

    uses: arduino/compile-sketches@v1

Additional context

• Issue identified here: Expand CI coverage to four examples from the Nicla Sense ME User Manual nicla-sense-me-fw#139 (comment)
• Successful compilation/execution of Magnetometer.ino sketch locally confirmed by @mcmchris

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the latest version
• My report contains all necessary details

[per1234]

The reason for the different result from the local compilation is that you were using an operating system (Windows or macOS) with a case-insensitive filesystem. In this filesystem, the filenames Math.h and math.h are functionally equivalent in this usage and so the sketch is able to compile due to the standard library containing a math.h header:

https://cplusplus.com/reference/cmath/

The CI workflow run was in a Linux machine, which has a case-sensitive filesystem. In this type of filesystem, the filename Math.h is different from math.h, which causes the bug in the sketch caused the compilation to fail.

So this result is correct and expected, not a bug in the action.