Directory: add `import_single_file` method

This a new method which deals with importing a single file.
Implemented for both FileBasedDirectory and CasBasedDirectory.

Part of #983

3 files changed, 26 insertions, 0 deletions

diff --git a/src/buildstream/storage/_casbaseddirectory.py b/src/buildstream/storage/_casbaseddirectory.py
index 2aff29b98..12ef482dc 100644
--- a/src/buildstream/storage/_casbaseddirectory.py
+++ b/src/buildstream/storage/_casbaseddirectory.py
@@ -386,6 +386,18 @@ class CasBasedDirectory(Directory):
 
         return result
 
+    def import_single_file(self, srcpath):
+        result = FileListResult()
+        if self._check_replacement(os.path.basename(srcpath),
+                                   os.path.dirname(srcpath),
+                                   result):
+            self._add_file(os.path.dirname(srcpath),
+                           os.path.basename(srcpath),
+                           modified=os.path.basename(srcpath)
+                           in result.overwritten)
+            result.files_written.append(srcpath)
+        return result
+
     def set_deterministic_mtime(self):
         """ Sets a static modification time for all regular files in this directory.
         Since we don't store any modification time, we don't need to do anything.
diff --git a/src/buildstream/storage/_filebaseddirectory.py b/src/buildstream/storage/_filebaseddirectory.py
index 9a746f731..90911da86 100644
--- a/src/buildstream/storage/_filebaseddirectory.py
+++ b/src/buildstream/storage/_filebaseddirectory.py
@@ -28,6 +28,7 @@ See also: :ref:`sandboxing`.
 """
 
 import os
+import shutil
 import stat
 import time
 
@@ -111,6 +112,15 @@ class FileBasedDirectory(Directory):
                 os.utime(os.path.join(self.external_directory, f), times=(cur_time, cur_time))
         return import_result
 
+    def import_single_file(self, srcpath):
+        dstpath = os.path.join(self.external_directory, os.path.basename(srcpath))
+        result = FileListResult()
+        if os.path.exists(dstpath):
+            result.ignored.append(dstpath)
+        else:
+            shutil.copyfile(srcpath, dstpath, follow_symlinks=False)
+        return result
+
     def _mark_changed(self):
         pass
 
diff --git a/src/buildstream/storage/directory.py b/src/buildstream/storage/directory.py
index bad818fef..c40e1bdb9 100644
--- a/src/buildstream/storage/directory.py
+++ b/src/buildstream/storage/directory.py
@@ -103,6 +103,10 @@ class Directory():
 
         raise NotImplementedError()
 
+    def import_single_file(self, external_pathspec):
+        """Imports a single file from an external path"""
+        raise NotImplementedError()
+
     def export_files(self, to_directory, *, can_link=False, can_destroy=False):
         """Copies everything from this into to_directory.