feature: Added raw terminal support in monitor command

[cmaglie]

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What kind of change does this PR introduce?

Adds the --raw flag to the monitor command to put the terminal in raw mode.
When the terminal is in raw mode:

• Control chars are not processed
• Terminal is not line-buffered anymore (each char is sent as soon as the key is pressed)
• Sent chars are not echoed
• CR are not automatically added after NL LF are not automatically added after CR

This may result in weird behavior but it may be the desired result, for example, see #2251

What is the current behavior?

What is the new behavior?

$ cat Term.ino 
void setup() {
	Serial.begin(9600);
}

void loop() {
	while (Serial.available() > 0) {
		char c = Serial.read(); 

		if (c < 0x10) Serial.print("0");
		Serial.print(c, HEX);
		Serial.print(" ");

		if (c=='\r') Serial.println();
	}
	delay(10);
}
$ arduino-cli monitor -p /dev/ttyACM0 --config baudrate=9600 --raw
Monitor port settings:
baudrate=9600
Connected to /dev/ttyACM0! Press CTRL-C to exit.
6A 77 69 65 71 77 68 75 64 69 73 61 73 64 71 77 65 0D <----- data is printed as soon as keys are pressed
0D                                                    <----- key presses are not echoed back
0D 
73 6A 64 68 6A 73 64 68 71 6A 77 65 0D 
$ 

Does this PR introduce a breaking change, and is titled accordingly?

No

Other information

I've tested it on Linux only. More testing is needed especially on Windows.

Fix #2251

[codecov]

Codecov Report

Patch coverage: 18.75% and project coverage change: -0.14% ⚠️

Comparison is base (3f9373a) 63.40% compared to head (b7e4a39) 63.26%.
Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2291      +/-   ##
==========================================
- Coverage   63.40%   63.26%   -0.14%     
==========================================
  Files         219      218       -1     
  Lines       19536    19555      +19     
==========================================
- Hits        12386    12371      -15     
- Misses       6069     6099      +30     
- Partials     1081     1085       +4     

Flag	Coverage Δ
unit	63.26% <18.75%> (-0.14%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
internal/cli/feedback/terminal.go	9.09% <0.00%> (-2.68%)	⬇️
internal/cli/monitor/monitor.go	15.68% <23.68%> (+2.60%)	⬆️

... and 5 files with indirect coverage changes

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[alessio-perugini]

I've tested on:
Linux - ubuntu: ✔️
Windows 11: ✔️

[oscherler]

You mention that in raw mode, “CR are not automatically added after NL.” This confuses me on two levels:

1. Usually, CR appears before LF;
2. This sentence seems to imply that in normal mode, CR is added to new lines, but on my Mac, only LF is sent on new line (causing my old projects to break with arduino-cli.)

[cmaglie]

Usually, CR appears before LF;

You're right, the sequence is CR+LF, I've edited the post.

This sentence seems to imply that in normal mode, CR is added to new lines, but on my Mac, only LF is sent on new line (causing my old projects to break with arduino-cli.)

In raw mode, the OS terminal emulation is bypassed, and when you press the "Enter" key, the CLI gets directly the 0x0D char code and sends it to the serial port without further processing.

In non-raw mode, the terminal emulator does some processing before the character reaches arduino-cli, on my Linux box "Enter" is translated into a CR+LF sequence (my Linux terminal emulation is xterm-256color it may be different on other OS).