Implement pkg_install(symlink) (#979)

* Implement pkg_install(symlink)

A first attempt at pgk_install of symlinks.
It was pretty obvious code once I realized I needed os.lchmod()

* fix use of cc_binary in the test because things changed under us

* old python on buildkit

* revert unintentional python reformating

* Update pkg/private/install.py.tpl

Co-authored-by: Andrew Psaltis <[email protected]>

---------

Co-authored-by: Andrew Psaltis <[email protected]>

Author: aiuto

pkg/private/install.py.tpl

@@ -99,7 +99,21 @@ class NativeInstaller(object):
         os.makedirs(dirname, int(mode, 8), exist_ok=True)
 
     def _do_symlink(self, target, link_name, mode, user, group):
-        raise NotImplementedError("symlinking not yet supported")
+        logging.debug("SYMLINK %s <- %s", link_name, target)
+        os.symlink(target, link_name)
+        if mode:
+            if hasattr(os, "lchmod"):
+                 logging.debug("CHMOD %s %s", mode, link_name)
+                 os.lchmod(link_name, int(mode, 8))
+            else:
+                 logging.debug("CHMOD-NOT AVAILABLE %s %s", mode, link_name)
+        if user or group:
+            # Ownership can only be changed by sufficiently
+            # privileged users.
+            # TODO(nacl): This does not support windows
+            if hasattr(os, "lchown") and os.getuid() == 0:
+                logging.debug("CHOWN %s:%s %s", user, group, link_name)
+                os.lchown(link_name, user, group)
 
     def _maybe_make_unowned_dir(self, path):
         logging.debug("MKDIR (unowned) %s", path)
@@ -161,10 +175,8 @@ class NativeInstaller(object):
         self._chown_chmod(entry.dest, top_dir_mode, entry.user, entry.group)
 
     def _install_symlink(self, entry):
-        raise NotImplementedError("symlinking not yet supported")
-        logging.debug("SYMLINK %s <- %s", entry.dest, entry.link_to)
-        logging.debug("CHMOD %s %s", entry.dest, entry.mode)
-        logging.debug("CHOWN %s.%s %s", entry.dest, entry.user, entry.group)
+        self._maybe_make_unowned_dir(os.path.dirname(entry.dest))
+        self._do_symlink(entry.src, entry.dest, entry.mode, entry.user, entry.group)
 
     def include_manifest_path(self, path):
         with open(path, 'r') as fh:

tests/install/BUILD

@@ -14,7 +14,7 @@
 
 load("@rules_python//python:defs.bzl", "py_test")
 load("//pkg:install.bzl", "pkg_install")
-load("//pkg:mappings.bzl", "pkg_attributes", "pkg_files", "pkg_mkdirs")
+load("//pkg:mappings.bzl", "pkg_attributes", "pkg_files", "pkg_mkdirs", "pkg_mklink")
 load("//tests/util:defs.bzl", "directory", "fake_artifact")
 
 package(default_applicable_licenses = ["//:license"])
@@ -47,6 +47,8 @@ pkg_install(
         ":artifact-in-owned-dir",
         ":artifact-in-unowned-dir",
         ":dirs",
+        ":fake_lib_link",
+        ":fake_so_in_lib",
         ":generate_tree_pkg_files",
     ],
 )
@@ -97,3 +99,19 @@ pkg_files(
         mode = "640",
     ),
 )
+
+fake_artifact(
+    name = "fake.so.1.2.3",
+)
+
+pkg_files(
+    name = "fake_so_in_lib",
+    srcs = [":fake.so.1.2.3"],
+    prefix = "/lib",
+)
+
+pkg_mklink(
+    name = "fake_lib_link",
+    link_name = "/lib/fake.so.1",
+    target = "fake.so.1.2.3",
+)

tests/install/test.py

@@ -87,7 +87,7 @@ def assertEntryModeMatches(self, entry, actual_path,
         if os.name == 'nt':
             return
 
-        actual_mode = stat.S_IMODE(os.stat(actual_path).st_mode)
+        actual_mode = stat.S_IMODE(os.stat(actual_path, follow_symlinks=False).st_mode)
         expected_mode = int(entry.mode, 8)
 
         if (not is_tree_artifact_content and

tests/rpm/BUILD

@@ -15,6 +15,7 @@
 
 load("@bazel_skylib//rules:build_test.bzl", "build_test")
 load("@bazel_skylib//rules:diff_test.bzl", "diff_test")
+load("@rules_cc//cc:cc_binary.bzl", "cc_binary")
 load("@rules_python//python:defs.bzl", "py_library", "py_test")
 load("@rules_shell//shell:sh_library.bzl", "sh_library")
 load(