Fixes to get rules_pkl to pass for larger projects (#31)

* Correct cache directory for `pkl_test` and `pkl_test_suite` targets

These two targets appear to receive an incorrect (relative) path for
the cache directory.

They're prefixed with the `ctx.genfiles_dir.path` and this leads to an
error when providing a `pkl_project` repository alongside any number
of `pkl_library` targets as dependencoes.

* Copy files, don't symlink them so that Pkl can pick them up

We have lots of symlinks within the `--working-dir` that we pass to
Pkl. This means that any code that's using globbed reads `read*`,
or globbed imports `import*` can’t find the files that it requires.

This has been something that Pkl (and Pcl before it) haven’t
supported, so I’m curious how we ended up with this regression or what
we did. Here’s the bit of code in Pkl where symlinks are ignored:
https://github.com/apple/pkl/blob/e81a47a03807739f8ab69eb8c595b53ec0afb434/pkl-core/src/main/java/org/pkl/core/module/FileResolver.java#L39-L42

Not having a solution for this will be a deal breaker for some
projects as they will have a number of `pkl_library` targets that
they progressively depend upon and expect to have present when we
`pkl_eval` or `pkl_test`.

My understanding is that supporting this in Pkl is non-trivial right
now, and requires work on cycle detection.

I’ve provided a patch to the `Symlinks.java` code which copies files
over rather than symlinking them.

* Allow up to 80% of RAM to be used

Co-authored-by: Kushal Pisavadia <[email protected]>

pkl/BUILD.bazel

@@ -99,6 +99,9 @@ toolchain(
 
 java_binary(
     name = "pkl_cli_java",
+    jvm_flags = [
+        "-XX:MaxRAMPercentage=80.0",
+    ],
     main_class = "org.pkl.cli.Main",
     runtime_deps = [
         artifact(

pkl/private/org/pkl_lang/bazel/symlinks/Symlinks.java

@@ -60,7 +60,7 @@ public static void main(String[] args) throws IOException {
                 }
 
                 Files.createDirectories(link.getParent());
-                Files.createSymbolicLink(link, target);
+                Files.copy(target, link);
             }
         }
     }

pkl/private/pkl.bzl

@@ -62,6 +62,10 @@ def _prepare_pkl_script(ctx, is_test_target):
                 path_to_symlink_target[file.path] = path
 
     cache_root_path, caches, cache_deps = root_caches_and_dependencies(ctx.attr.srcs + ctx.attr.deps)
+
+    if is_test_target and cache_root_path != None:
+        cache_root_path = cache_root_path.removeprefix(ctx.genfiles_dir.path)[1:]
+
     if len(caches):
         path_to_symlink_target[caches[0].pkl_project.path] = "%s/PklProject" % working_dir
         path_to_symlink_target[caches[0].pkl_project_deps.path] = "%s/PklProject.deps.json" % working_dir