BaseReportWriter fails with "No source root found" when source uses symbolic links

[nickweeds]

Problem:
I have an sbt project that collects code coverage for source code in another project that it picks up using a symbolic link of the form
ln -s {external_root}/{project}/src/main {root}/{project}/src/main
Everything works fine until I run "sbt coverageReport", but that fails with an error of the form:
No source root found for '{root}/{project}/src/main/.../{source.scala}' (source roots: '{external_root}/{project}/src/main/scala/', ...')

Diagnosis:
The failure occurs because BaseReportWriter applies _.getCanonicalPath to sourceDirectories (when initializing formattedSourcePaths) but not to the source file in relativeSource().

Fix:
I think this can be fixed in relativeSource() by applying getCanonicalPath to the source file name before searching sourcePaths.

[gslowikowski]

For readers convenience, we are talking about BaseReportWriter class.

I implemented relativeSource method. In fact the easiest way to fix this bug would be to map src to new File(src).getCanonicatPath but I generally don't like calling getCanonicalPath if not absolutely needed.

getCanonicalPath was here since version 1.0.0 (this commit), but why was it introduced there? @sksamuel, do you remember?
Because it was here for so long, I left it here.

src parameter in relativeSource method comes from Statement.source.path and represents absolute path, not canonical. It comes from the internals of Scalac. I cannot find, where and how it's created.
Maybe we could change

  private val formattedSourcePaths: Seq[String] = sourceDirectories filter ( _.isDirectory ) map ( _.getCanonicalPath + File.separator )

to

  private val formattedSourcePaths: Seq[String] = sourceDirectories filter ( _.isDirectory ) map ( _.getAbsolutePath + File.separator )

instead of adding getCanonicalPath mapping to src parameter? This additionally should improve performance.

I can change it and publish new snapshot to test. WDYT?

[gslowikowski]

Fixed by #159