[native_toolchain_c] Changes to header files should be added to the dependencies

[dcharkes]

The CBuilder lists the C sources, but not the header files.

native/pkgs/native_assets_cli/example/build/native_add_library/hook/build.dart

Lines 12 to 19 in 952da66

	final cbuilder = CBuilder.library(
	name: packageName,
	assetName: '$packageName.dart',
	sources: [
	'src/$packageName.c',
	],
	dartBuildFiles: ['hook/build.dart'],
	);

This means the headers are not added to the dependencies. Which means that any changes to the header files do not cause cache invalidation.

Thanks for the feedback @SaltySpaghetti!

Possible solutions:

1. Pass in the .h files to sources, which will add them to the compiler invocation (which is fine for clang-like compiler).
   • Pro: Clanglike compilers can optimize if we pass the .h files to the compilation step. https://gcc.gnu.org/onlinedocs/gcc/Precompiled-Headers.html
   • Not every compiler might like this. We can work around this by filtering .h files out.
   • Pro: Similar design to GN/ninja, which also have the c and h files in a flat list.
2. Add the header directory to the includes (ty @blaugold!)
3. Add a List<String> headers parameter/field. Which would only resolve the list of paths and add it to the BuildOutput dependencies.
   • Pro: most to the point.
   • Con: if there's other dependencies which are not header files this parameter can be used to shoe-horn these deps in.
4. Add a List<String> dependencies parameter/field.

• Con: Is not as discoverable as headers.

I'm leaning towards option 1.

A PR would contain:

• Updating all example/test projects to include the header files in sources:
• Adding some documentation to sources that it should include header files.
• If needed for some compilers, filtering out .h files in the compiler invocation.

[blaugold]

Just FYI, includes adds all files that are contained in the provided directories to dependencies. So you could just add the directory with the headers to includes.

native/pkgs/native_toolchain_c/lib/src/cbuilder/cbuilder.dart

Lines 66 to 71 in 7efefec

	/// Include directories to pass to the compiler.
	///
	/// Resolved against [BuildConfig.packageRoot].
	///
	/// Used to output the [BuildOutput.dependencies].
	final List<String> includes;

[dcharkes]

Just FYI, includes adds all files that are contained in the provided directories to dependencies. So you could just add the directory with the headers to includes.

native/pkgs/native_toolchain_c/lib/src/cbuilder/cbuilder.dart

Lines 66 to 71 in 7efefec

	/// Include directories to pass to the compiler.
	///
	/// Resolved against [BuildConfig.packageRoot].
	///
	/// Used to output the [BuildOutput.dependencies].
	final List<String> includes;

Thanks @blaugold!
If option 1 works though, I believe that option 1 is better. But if there's issues with option 1, than option 2 is a good one too.

[MiniPiku]

@dcharkes kindly take a look at the changes made
#2098
thank you :)