Output of compile --preprocess is different from the file generated with the Arduino app

[spoenemann]

Bug Report

Current behavior

I created a new sketch sketch_july2a with the default content (empty setup and loop functions).
The command

arduino-cli compile --preprocess --fqbn arduino:avr:uno sketch_july2a.ino

gives me the following output (full path of source file replaced with ...):

# 1 ".../sketch_july2a.ino"
# 1 ".../sketch_july2a.ino"
# 2 ".../sketch_july2a.ino"
void setup();
# 7 ".../sketch_july2a.ino"
void loop();
# 2 ".../sketch_july2a.ino"
void setup() {
    // put your setup code here, to run once:

}

void loop() {
    // put your main code here, to run repeatedly:

}

Expected behavior

The generated C++ code is missing #include <Arduino.h>, and the source file and line number instructions should start with #line.

This is the result of compiling the sketch with the Arduino app, which I would also expect as output of the arduino-cli command above:

#include <Arduino.h>
#line 1 ".../sketch_july2a.ino"
#line 1 ".../sketch_july2a.ino"

#line 2 ".../sketch_july2a.ino"
void setup();
#line 7 ".../sketch_july2a.ino"
void loop();
#line 2 ".../sketch_july2a.ino"
void setup() {
    // put your setup code here, to run once:
    
}

void loop() {
    // put your main code here, to run repeatedly:
    
}

Environment

• CLI version: 0.3.7-alpha.preview (built from branch massi/preprocess Fix compile error when --preprocess or --show-properties were passed #331)
• Go version: go1.12.7
• OS version: macOS 10.14.6

Additional context

I'd like to get the C++ code that is generated as an intermediate step when compiling a sketch.

[spoenemann]

This is what I get by running the arduino-cli compile command without --preprocess and looking for the C++ code in the temp folder:

#include <Arduino.h>
#line 1 ".../sketch_july2a.ino"

void setup() {
    // put your setup code here, to run once:
    
}

void loop() {
    // put your main code here, to run repeatedly:
    
}

It's better than with --preprocess because the #include and #line directives are correct, but it's still different from the original output: it's missing the forward declaration of local procedures.

In any case, I would expect the C++ code to be the same with and without the --preprocess flag.