Create an example of the kind of link tree Node users must create (#603)

* Create an example of the kind of link tree Node users muse create

pkg/private/pkg_files.bzl

@@ -127,12 +127,15 @@ def _process_pkg_symlink(content_map, pkg_symlink_info, origin, default_mode, de
     )
 
 def _process_pkg_filegroup(content_map, pkg_filegroup_info, origin, default_mode, default_user, default_group):
-    for d in pkg_filegroup_info.pkg_dirs:
-        _process_pkg_dirs(content_map, d[0], d[1], default_mode, default_user, default_group)
-    for pf in pkg_filegroup_info.pkg_files:
-        _process_pkg_files(content_map, pf[0], pf[1], default_mode, default_user, default_group)
-    for psl in pkg_filegroup_info.pkg_symlinks:
-        _process_pkg_symlink(content_map, psl[0], psl[1], default_mode, default_user, default_group)
+    if hasattr(pkg_filegroup_info, "pkg_dirs"):
+        for d in pkg_filegroup_info.pkg_dirs:
+            _process_pkg_dirs(content_map, d[0], d[1], default_mode, default_user, default_group)
+    if hasattr(pkg_filegroup_info, "pkg_files"):
+        for pf in pkg_filegroup_info.pkg_files:
+            _process_pkg_files(content_map, pf[0], pf[1], default_mode, default_user, default_group)
+    if hasattr(pkg_filegroup_info, "pkg_symlinks"):
+        for psl in pkg_filegroup_info.pkg_symlinks:
+            _process_pkg_symlink(content_map, psl[0], psl[1], default_mode, default_user, default_group)
 
 def process_src(content_map, files, src, origin, default_mode, default_user,
                 default_group):

tests/BUILD

@@ -39,6 +39,15 @@ filegroup(
     visibility = ["//visibility:public"],
 )
 
+filegroup(
+    name = "file_and_link",
+    srcs = [
+        "BUILD",
+        "testdata/outer_BUILD",
+    ],
+    visibility = ["//visibility:public"],
+)
+
 filegroup(
     name = "glob_for_texts",
     srcs = glob(["**/*.txt"]),

tests/mappings/BUILD

@@ -27,7 +27,7 @@ load(
     "pkg_mkdirs",
     "strip_prefix",
 )
-load("//tests/util:defs.bzl", "directory", "write_content_manifest")
+load("//tests/util:defs.bzl", "directory", "link_tree", "write_content_manifest")
 load("@rules_python//python:defs.bzl", "py_test")
 
 package(default_applicable_licenses = ["//:license"])
@@ -158,3 +158,30 @@ manifest_golden_test(
     expected = "glob_for_texts_manifest.golden",
     target = "glob_for_texts_manifest",
 )
+
+link_tree(
+    name = "node_modules",
+    links = {
+        "foo": ".pnpm/foo@1.0.0/node_modules/foo",
+        ".pnpm/bar@1.0.0/node_modules/bar": "STORE/bar",
+        ".pnpm/bar@1.0.0/node_modules/qar": "../../qar@2.0.0/node_modules/qar",
+        ".pnpm/foo@1.0.0/node_modules/foo": "STORE/foo",
+        ".pnpm/foo@1.0.0/node_modules/bar": "../../bar@1.0.0/node_modules/bar",
+        ".pnpm/foo@1.0.0/node_modules/qar": "../../qar@2.0.0/node_modules/qar",
+        ".pnpm/qar@2.0.0/node_modules/qar": "STORE/qar",
+    },
+    package_dir = "node_modules",
+)
+
+write_content_manifest(
+    name = "node_modules_manifest",
+    srcs = [
+        ":node_modules",
+    ],
+)
+
+manifest_golden_test(
+    name = "link_tree_test",
+    expected = "node_modules_manifest.golden",
+    target = "node_modules_manifest",
+)

tests/mappings/node_modules_manifest.golden

@@ -0,0 +1,9 @@
+[
+[1,"node_modules/.pnpm/bar@1.0.0/node_modules/bar","STORE/bar","",null,null],
+[1,"node_modules/.pnpm/bar@1.0.0/node_modules/qar","../../qar@2.0.0/node_modules/qar","",null,null],
+[1,"node_modules/.pnpm/foo@1.0.0/node_modules/bar","../../bar@1.0.0/node_modules/bar","",null,null],
+[1,"node_modules/.pnpm/foo@1.0.0/node_modules/foo","STORE/foo","",null,null],
+[1,"node_modules/.pnpm/foo@1.0.0/node_modules/qar","../../qar@2.0.0/node_modules/qar","",null,null],
+[1,"node_modules/.pnpm/qar@2.0.0/node_modules/qar","STORE/qar","",null,null],
+[1,"node_modules/foo",".pnpm/foo@1.0.0/node_modules/foo","",null,null]
+]

tests/tar/BUILD

@@ -18,11 +18,14 @@
 load("//pkg:mappings.bzl", "pkg_files", "strip_prefix")
 load("//pkg/private/tar:tar.bzl", "SUPPORTED_TAR_COMPRESSIONS", "pkg_tar")
 load("//tests:my_package_name.bzl", "my_package_naming")
-load("//tests/util:defs.bzl", "directory", "fake_artifact")
+load("//tests/util:defs.bzl", "directory", "link_tree", "fake_artifact")
 load("@rules_python//python:defs.bzl", "py_test")
 load("@bazel_skylib//rules:copy_file.bzl", "copy_file")
 
-package(default_applicable_licenses = ["//:license"])
+package(
+    default_applicable_licenses = ["//:license"],
+    default_visibility = ["//visibility:private"],
+)
 
 py_test(
     name = "tar_writer_test",
@@ -396,3 +399,49 @@ py_test(
         "@bazel_tools//tools/python/runfiles",
     ],
 )
+
+link_tree(
+    name = "node_modules",
+    links = {
+        "foo": ".pnpm/foo@1.0.0/node_modules/foo",
+        ".pnpm/bar@1.0.0/node_modules/bar": "STORE/bar",
+        ".pnpm/foo@1.0.0/node_modules/foo": "STORE/foo",
+        ".pnpm/foo@1.0.0/node_modules/bar": "../../bar@1.0.0/node_modules/bar",
+    },
+    package_dir = "node_modules",
+)
+
+directory(
+    name = "tree_artifact_with_links",
+    contents = "hello there",
+    filenames = [
+        "foo/hello.txt",
+        "foo/bar/baz",
+    ],
+    links = {
+        "foo/bar/hello":  "../hello.txt",
+        "foo/bar/alt_baz":  "baz",
+        "foo/alt_baz":  "bar/baz",
+    },
+)
+
+
+# This target has symlinks 3 ways.
+# - mklinks rules.
+# - source files that are symlinks
+# - tree artifacts
+pkg_tar(
+    name = "relative_links_tar",
+    srcs = [
+        ":node_modules",
+        ":tree_artifact_with_links",
+        "//tests:file_and_link",
+    ],
+)
+
+pkg_tar(
+    name = "relative_links_re_tar",
+    deps = [
+        ":relative_links_tar",
+    ],
+)

tests/testdata/outer_BUILD

@@ -0,0 +1 @@
+../BUILD

tests/util/create_directory_with_contents.py

@@ -36,9 +36,13 @@
 os.makedirs(dirname, exist_ok=True)
 
 for fname, contents in files_contents_map.items():
+    path = os.path.join(dirname, fname)
     os.makedirs(
-        os.path.join(dirname, os.path.dirname(fname)),
+        os.path.dirname(path),
         exist_ok=True,
     )
-    with open(os.path.join(dirname, fname), 'w') as fh:
-        fh.write(contents)
+    if contents.startswith('@@'):
+        os.symlink(contents[2:], path)
+    else:
+        with open(path, 'w') as fh:
+            fh.write(contents)

tests/util/defs.bzl

@@ -15,6 +15,7 @@
 """Rules to aid testing"""
 
 load("//pkg/private:pkg_files.bzl", "add_label_list", "write_manifest")
+load("//pkg:providers.bzl", "PackageFilegroupInfo", "PackageSymlinkInfo")
 load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")
 load("@rules_python//python:defs.bzl", "py_binary")
 
@@ -24,10 +25,15 @@ def _directory_impl(ctx):
     args = ctx.actions.args()
     args.add(out_dir_file.path)
 
+    # This helper is horrible.  We should pass all the args in files.
     for fn in ctx.attr.filenames:
         args.add(fn)
         args.add(ctx.attr.contents)
 
+    for link, target in ctx.attr.links.items():
+        args.add(link)
+        args.add('@@' + target)
+
     ctx.actions.run(
         outputs = [out_dir_file],
         inputs = [],
@@ -48,6 +54,11 @@ creation capabilities are "unsound".
             doc = """Paths to create in the directory.
 
 Paths containing directories will also have the intermediate directories created too.""",
+        ),
+        "links": attr.string_dict(
+            doc = """Set of (virtual) links to create.
+
+The keys of links are paths to create.  The values are the target of the links.""",
         ),
         "contents": attr.string(),
         "outdir": attr.string(),
@@ -101,6 +112,37 @@ cc_binary in complexity, but does not depend on a large toolchain.""",
     },
 )
 
+def _link_tree_impl(ctx):
+    links = []
+    prefix = ctx.attr.package_dir or ""
+    if prefix and not prefix.endswith('/'):
+        prefix = prefix + "/"
+    for link, target in ctx.attr.links.items():
+        print('  %s -> %s ' % (link, target))
+        links.append(
+            (PackageSymlinkInfo(destination = prefix + link, target = target),
+             ctx.label))
+    return [PackageFilegroupInfo(pkg_symlinks = links)]
+
+link_tree = rule(
+    doc = """Helper rule to create a lot of fake symlinks.
+
+The inspiration is to create test data for the kinds of layouts needed by
+nodejs.  See. https://pnpm.io/symlinked-node-modules-structure
+    """,
+    implementation = _link_tree_impl,
+    attrs = {
+        "links": attr.string_dict(
+            doc = """Set of (virtual) links to create.
+
+The keys of links are paths to create.  The values are the target of the links.""",
+            mandatory = True,
+        ),
+        "package_dir": attr.string(doc = """Prefix to apply to all link paths."""),
+    },
+    provides = [PackageFilegroupInfo],
+)
+
 def _write_content_manifest_impl(ctx):
     content_map = {}  # content handled in the manifest
     file_deps = []  # inputs we depend on