utils.py: Change _ensure_real_directory() to not resolve symlinks

Resolving symlinks during staging causes various issues:

* Split rules may not work properly as the resolved paths will differ
  depending on whether another artifact with a directory symlink has
  been staged in the same root directory or not, e.g., as part of
  compose.

* The order of symlinks in file lists is difficult to get right to
  guarantee consistent and predictable behavior as paths in a file list
  might rely on symlinks in the same file list. See #647 and #817.

* Staging order differences can lead to surprising results. See #390.

* Difficult to properly support absolute symlinks. Absolute symlinks are
  currently converted to relative symlinks, however, this doesn't always
  work. See #606 and #830.

This will require changes in projects that rely on the current behavior.
However, the changes are expected to be small and are often a sign of
buggy element files. E.g., elements that don't fully obey `bindir` or
`sbindir` variables.

2 files changed, 7 insertions, 14 deletions

diff --git a/tests/integration/compose-symlinks.py b/tests/integration/compose-symlinks.py
index c6027bf2b..027feea7c 100644
--- a/tests/integration/compose-symlinks.py
+++ b/tests/integration/compose-symlinks.py
@@ -18,7 +18,7 @@ DATA_DIR = os.path.join(
 )
 
 
-# Test that staging a file inside a directory symlink works as expected.
+# Test that staging a file inside a directory symlink fails.
 #
 # Regression test for https://gitlab.com/BuildStream/buildstream/issues/270
 @pytest.mark.datafiles(DATA_DIR)
@@ -34,11 +34,6 @@ def test_compose_symlinks(cli, tmpdir, datafiles):
     os.symlink(os.path.join('usr', 'sbin'), symlink_file, target_is_directory=True)
 
     result = cli.run(project=project, args=['build', 'compose-symlinks/compose.bst'])
-    result.assert_success()
 
-    result = cli.run(project=project, args=['artifact', 'checkout', 'compose-symlinks/compose.bst',
-                                            '--directory', checkout])
-    result.assert_success()
-
-    assert set(walk_dir(checkout)) == set(['/sbin', '/usr', '/usr/sbin',
-                                           '/usr/sbin/init', '/usr/sbin/dummy'])
+    assert result.exit_code == -1
+    assert 'Destination is a symlink, not a directory: /sbin' in result.stderr
diff --git a/tests/integration/symlinks.py b/tests/integration/symlinks.py
index 22ff527f8..5674b5778 100644
--- a/tests/integration/symlinks.py
+++ b/tests/integration/symlinks.py
@@ -44,7 +44,7 @@ def test_absolute_symlinks_made_relative(cli, tmpdir, datafiles):
 
 @pytest.mark.datafiles(DATA_DIR)
 @pytest.mark.skipif(not HAVE_SANDBOX, reason='Only available with a functioning sandbox')
-def test_allow_overlaps_inside_symlink_with_dangling_target(cli, tmpdir, datafiles):
+def test_disallow_overlaps_inside_symlink_with_dangling_target(cli, tmpdir, datafiles):
     project = os.path.join(datafiles.dirname, datafiles.basename)
     checkout = os.path.join(cli.directory, 'checkout')
     element_name = 'symlinks/dangling-symlink-overlap.bst'
@@ -53,10 +53,8 @@ def test_allow_overlaps_inside_symlink_with_dangling_target(cli, tmpdir, datafil
     assert result.exit_code == 0
 
     result = cli.run(project=project, args=['artifact', 'checkout', element_name, '--directory', checkout])
-    assert result.exit_code == 0
-
-    # See the dangling-symlink*.bst elements for details on what we are testing.
-    assert_contains(checkout, ['/usr/orgs/orgname/etc/org.conf'])
+    assert result.exit_code == -1
+    assert 'Destination is a symlink, not a directory: /opt/orgname' in result.stderr
 
 
 @pytest.mark.datafiles(DATA_DIR)
@@ -75,4 +73,4 @@ def test_detect_symlink_overlaps_pointing_outside_sandbox(cli, tmpdir, datafiles
     # tries to actually write there.
     result = cli.run(project=project, args=['artifact', 'checkout', element_name, '--directory', checkout])
     assert result.exit_code == -1
-    assert "Destination path resolves to a path outside of the staging area" in result.stderr
+    assert 'Destination is a symlink, not a directory: /opt/escape-hatch' in result.stderr