Auto Format makes functional changes to sketch code

[Pexje]

Describe the problem

When using Auto Format in Arduino IDE 2.0.1 some code in beginning of sketch goes wrong:

This gives Compilation error.

To reproduce

Please fix this bug.

Expected behavior

This is good working code before using Auto Format:

Arduino IDE version

2.0.1

Operating system

Windows

Operating system version

11

Additional context

No response

Issue checklist

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

[per1234]

Thanks for your report @Pexje.

This gives Compilation error.

Although I am able to reproduce the formatting change you describe:

before

#define DEBUG_SERIAL if (DEBUG) Serial

after

#define DEBUG_SERIAL \
  if (DEBUG) Serial

I am not able to reproduce the compilation error you claim. I will need you to provide enough information for me to reproduce it:

• A complete minimal sketch that compiles before formatting and does not compile after formatting.
• Does the problem occur if you select Tools > Board > Arduino AVR Boards > Arduino Uno from the Arduino IDE menus before compiling the formatted sketch? If not, which board do you have selected when compilation does fail?
• The full an exact text of the compiler error message shown in the "Output" panel at the bottom of the Arduino IDE window.

Investigation

I looked for a setting in the ClangFormat options (ClangFormat is the tool used by the Arduino IDE "Auto Format" feature) that would cause it to not add this line break. I did not find any.

It is not clear whether the addition of this break is intentional behavior of the formatter or a bug. I found this similar bug report: llvm/llvm-project#53180. I also found this related bug report llvm/llvm-project#49164, which has been fixed, but that fix did not fix the problem you report here.

A more minimal demonstration code:

#define FOO if(true) {}
#define BAR while(true) {}
#define BAZ for(;;) {}

Formats to:

#define FOO \
  if (true) {}
#define BAR \
  while (true) {}
#define BAZ \
  for (;;) {}

Workaround

You can selectively disable formatting by adding special comments to your sketch code:

https://releases.llvm.org/14.0.0/tools/clang/docs/ClangFormatStyleOptions.html#disabling-formatting-on-a-piece-of-code

So if you don't like the line break, you can do this:

// clang-format off
#define DEBUG_SERIAL if (DEBUG) Serial
// clang-format on

[per1234]

Hi @Pexje. We are still waiting for you to provide the information requested in the previous reply so that we can proceed with the investigation or evaluation of this.

[per1234]

Since the requested code demonstrating a functional change to the code was never provided, and since the formatting style is not objectively bad from an aesthetic standpoint, I will close this as declined/invalid.

If someone can provide a sketch that demonstrates the changed formatting causing a functional change to the code then we will investigate further.