From 455323471868f653b0a305b9dc7d2a2dde2b9753 Mon Sep 17 00:00:00 2001
From: William Salmon <will.salmon@codethink.co.uk>
Date: Thu, 30 May 2019 13:37:02 +0100
Subject: Fix descend can not follow symlinks

---
 src/buildstream/storage/_casbaseddirectory.py  | 51 ++++++++++++++++++++++++--
 src/buildstream/storage/_filebaseddirectory.py |  6 ++-
 src/buildstream/storage/directory.py           |  2 +-
 3 files changed, 53 insertions(+), 6 deletions(-)

(limited to 'src/buildstream/storage')

diff --git a/src/buildstream/storage/_casbaseddirectory.py b/src/buildstream/storage/_casbaseddirectory.py
index 7bd9ceea0..424b7ef63 100644
--- a/src/buildstream/storage/_casbaseddirectory.py
+++ b/src/buildstream/storage/_casbaseddirectory.py
@@ -159,7 +159,15 @@ class CasBasedDirectory(Directory):
 
         self.__invalidate_digest()
 
-    def descend(self, *paths, create=False):
+    def find_root(self):
+        """ Finds the root of this directory tree by following 'parent' until there is
+        no parent. """
+        if self.parent:
+            return self.parent.find_root()
+        else:
+            return self
+
+    def descend(self, *paths, create=False, follow_symlinks=False):
         """Descend one or more levels of directory hierarchy and return a new
         Directory object for that directory.
 
@@ -177,6 +185,7 @@ class CasBasedDirectory(Directory):
         """
 
         current_dir = self
+        paths = list(paths)
 
         for path in paths:
             # Skip empty path segments
@@ -184,20 +193,37 @@ class CasBasedDirectory(Directory):
                 continue
 
             entry = current_dir.index.get(path)
+
             if entry:
                 if entry.type == _FileType.DIRECTORY:
                     current_dir = entry.get_directory(current_dir)
+                elif follow_symlinks and entry.type == _FileType.SYMLINK:
+                    linklocation = entry.target
+                    newpaths = linklocation.split(os.path.sep)
+                    if os.path.isabs(linklocation):
+                        current_dir = current_dir.find_root().descend(*newpaths, follow_symlinks=True)
+                    else:
+                        current_dir = current_dir.descend(*newpaths, follow_symlinks=True)
                 else:
                     error = "Cannot descend into {}, which is a '{}' in the directory {}"
                     raise VirtualDirectoryError(error.format(path,
                                                              current_dir.index[path].type,
-                                                             current_dir))
+                                                             current_dir),
+                                                reason="not-a-directory")
             else:
-                if create:
+                if path == '.':
+                    continue
+                elif path == '..':
+                    if current_dir.parent is not None:
+                        current_dir = current_dir.parent
+                    # In POSIX /.. == / so just stay at the root dir
+                    continue
+                elif create:
                     current_dir = current_dir._add_directory(path)
                 else:
                     error = "'{}' not found in {}"
-                    raise VirtualDirectoryError(error.format(path, str(current_dir)))
+                    raise VirtualDirectoryError(error.format(path, str(current_dir)),
+                                                reason="directory-not-found")
 
         return current_dir
 
@@ -618,6 +644,23 @@ class CasBasedDirectory(Directory):
 
         return self.__digest
 
+    def _exists(self, *path, follow_symlinks=False):
+        try:
+            subdir = self.descend(*path[:-1], follow_symlinks=follow_symlinks)
+            target = subdir.index.get(path[-1])
+            if target is not None:
+                if target.type == _FileType.REGULAR_FILE:
+                    return True
+                elif follow_symlinks and target.type == _FileType.SYMLINK:
+                    linklocation = target.target
+                    newpath = linklocation.split(os.path.sep)
+                    if os.path.isabs(linklocation):
+                        return subdir.find_root()._exists(*newpath, follow_symlinks=True)
+                    return subdir._exists(*newpath, follow_symlinks=True)
+            return False
+        except VirtualDirectoryError:
+            return False
+
     def __invalidate_digest(self):
         if self.__digest:
             self.__digest = None
diff --git a/src/buildstream/storage/_filebaseddirectory.py b/src/buildstream/storage/_filebaseddirectory.py
index 8c55819c9..a083f6507 100644
--- a/src/buildstream/storage/_filebaseddirectory.py
+++ b/src/buildstream/storage/_filebaseddirectory.py
@@ -37,6 +37,7 @@ from .. import utils
 from ..utils import link_files, copy_files, list_relative_paths, _get_link_mtime, BST_ARBITRARY_TIMESTAMP
 from ..utils import _set_deterministic_user, _set_deterministic_mtime
 from ..utils import FileListResult
+from .._exceptions import ImplError
 
 # FileBasedDirectory intentionally doesn't call its superclass constuctor,
 # which is meant to be unimplemented.
@@ -47,9 +48,12 @@ class FileBasedDirectory(Directory):
     def __init__(self, external_directory=None):
         self.external_directory = external_directory
 
-    def descend(self, *paths, create=False):
+    def descend(self, *paths, create=False, follow_symlinks=False):
         """ See superclass Directory for arguments """
 
+        if follow_symlinks:
+            ImplError("FileBasedDirectory.Decend dose not implement follow_symlinks=True")
+
         current_dir = self
 
         for path in paths:
diff --git a/src/buildstream/storage/directory.py b/src/buildstream/storage/directory.py
index c9906b058..d32ac0063 100644
--- a/src/buildstream/storage/directory.py
+++ b/src/buildstream/storage/directory.py
@@ -52,7 +52,7 @@ class Directory():
     def __init__(self, external_directory=None):
         raise NotImplementedError()
 
-    def descend(self, *paths, create=False):
+    def descend(self, *paths, create=False, follow_symlinks=False):
         """Descend one or more levels of directory hierarchy and return a new
         Directory object for that directory.
 
-- 
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