The supported file extensions of additional code files are not in sync with the spec

[kittaakos]

Describe the problem

Originally from here:

I have noticed that the spec, IDE2 code, and the CLI are not in sync regarding the allowed code file extensions:

• Spec: https://arduino.github.io/arduino-cli/dev/sketch-specification/#additional-code-files
• IDE2: https://github.com/arduino/arduino-ide/blob/6140ae525c57f99878e8fcd39727c1966ecf6a84/arduino-ide-extension/src/common/protocol/sketches-service.ts#L175-L179
• CLI:

  arduino-cli/arduino/globals/globals.go

  Lines 31 to 58 in a58d5ad

  	// AdditionalFileValidExtensions lists any file extension the builder considers as valid
  	AdditionalFileValidExtensions = map[string]struct{}{
  	".h": empty,
  	".c": empty,
  	".hpp": empty,
  	".hh": empty,
  	".cpp": empty,
  	".S": empty,
  	".adoc": empty,
  	".md": empty,
  	".json": empty,
  	".tpp": empty,
  	".ipp": empty,
  	}
  	// SourceFilesValidExtensions lists valid extensions for source files (no headers)
  	SourceFilesValidExtensions = map[string]struct{}{
  	".c": empty,
  	".cpp": empty,
  	".S": empty,
  	}
  	// HeaderFilesValidExtensions lists valid extensions for header files
  	HeaderFilesValidExtensions = map[string]struct{}{
  	".h": empty,
  	".hpp": empty,
  	".hh": empty,
  	}

To reproduce

Check the CLI code, the IDE2 code, and the spec: they are three different things.

Expected behavior

The code follows the spec, or the spec should be updated

Arduino CLI version

a58d5ad

Operating system

macOS

Operating system version

12.5.1

Additional context

No response

Issue checklist

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

[per1234]

The missing file extensions supported by Arduino CLI should be added to the specification:

• .hpp
• .hh

The tool versions that support these extensions should also be documented there.

---

Support for all file extensions listed in the specification should be added to Arduino IDE 2.x.