Replace getRelativePath with getNeighborPath in C++ code gen

[bocchino]

The C++ code generation uses the function getRelativePath to generate include paths for definitions in the model:

fpp/compiler/lib/src/main/scala/codegen/CppWriter/CppWriterState.scala

Lines 29 to 33 in 1ec4ecb

	/** Gets the relative path for a file */
	def getRelativePath(fileName: String): File.JavaPath = {
	val path = java.nio.file.Paths.get(fileName).toAbsolutePath.normalize
	removeLongestPathPrefix(path)
	}

For example, the ArrayCppWriter calls this function to generate the header file for the array class corresponding to the FPP array definition:

fpp/compiler/lib/src/main/scala/codegen/CppWriter/ArrayCppWriter.scala

Lines 100 to 106 in 1ec4ecb

	private def getCppIncludes: CppDoc.Member = {
	val userHeaders = List(
	"Fw/Types/Assert.hpp",
	s"${s.getRelativePath(fileName).toString}.hpp"
	).sorted.map(CppWriter.headerString).map(line)
	linesMember(Line.blank :: userHeaders, CppDoc.Lines.Cpp)
	}

This usage of getRelativePath is not actually correct, because it generates paths relative to the current directory (where fpp-to-cpp is run) instead of relative to the location of the definition. We should replace this and other calls to getRelativePath with calls to a new function getNeighborPath(symbol, fileName). This function can work like getIncludePath, which is correct:

fpp/compiler/lib/src/main/scala/codegen/CppWriter/CppWriterState.scala

Lines 122 to 131 in 1ec4ecb

	def getIncludePath(
	sym: Symbol,
	fileNameBase: String,
	headerExtension: String = "hpp"
	): String = {
	val loc = sym.getLoc.tuLocation
	val fullPath = loc.getNeighborPath(fileNameBase)
	val path = removeLongestPathPrefix(fullPath)
	s"${path.toString}.$headerExtension"
	}

We can refactor getIncludePath to use this function.

I believe this bug or anomaly in the code generation has never been noticed because we always run fpp-to-cpp at the location of the definition, so the current directory is the parent directory for the definition. However, if you run fpp-to-cpp foo/bar.fpp, you can see that the headers are generated relative to ., not relative to foo.

[bocchino]

I think we will need to keep getRelativePath for FppConstantsAc.hpp. That header is tied not to a symbol, but to the entire model. I think it's reasonable to assume in that case that the location of the header is the current directory where the code for the model is generated.