_workspaces.py: Remove knowledge of Elements completely

This makes workspaces more cleanly separated from everything else.

  o Removed some methods from Workspace()

  o Added Element._open_workspace() to initialize workspaces on
    sources

  o Cleanup some code in the pipeline

  o Have the App() call Element._open_workspace() instead of Workspace.open()

4 files changed, 50 insertions, 65 deletions

diff --git a/buildstream/_frontend/app.py b/buildstream/_frontend/app.py
index 14a8201d9..2d5842c32 100644
--- a/buildstream/_frontend/app.py
+++ b/buildstream/_frontend/app.py
@@ -427,14 +427,14 @@ class App():
         except OSError as e:
             raise AppError("Failed to create workspace directory: {}".format(e)) from e
 
-        workspace = self.project.workspaces.create_workspace(target, workdir)
+        workspace = self.project.workspaces.create_workspace(target.name, workdir)
 
         if not no_checkout:
             if not force and os.listdir(directory):
                 raise AppError("Checkout directory is not empty: {}".format(directory))
 
             with target.timed_activity("Staging sources to {}".format(directory)):
-                workspace.open()
+                target._open_workspace()
 
         self.project.workspaces.save_config()
         self.message(MessageType.INFO, "Saved workspace configuration")
diff --git a/buildstream/_pipeline.py b/buildstream/_pipeline.py
index 98ea6fbe8..969c3f6e5 100644
--- a/buildstream/_pipeline.py
+++ b/buildstream/_pipeline.py
@@ -80,7 +80,6 @@ class Pipeline():
         #
         # Private members
         #
-        self._unused_workspaces = []
         self._resolved_elements = {}
         self._redundant_refs = []
         self._artifacts = None
@@ -136,8 +135,6 @@ class Pipeline():
 
         self.total_elements = len(list(self.dependencies(Scope.ALL)))
 
-        self._initialize_workspaces()
-
         # Initialize remote artifact caches. We allow the commandline to override
         # the user config in some cases (for example `bst push --remote=...`).
         has_remote_caches = False
@@ -305,10 +302,10 @@ class Pipeline():
     #                        building
     #
     def build(self, scheduler, build_all, track_first):
-        if self._unused_workspaces:
+        unused_workspaces = self._collect_unused_workspaces()
+        if unused_workspaces:
             self._message(MessageType.WARN, "Unused workspaces",
-                          detail="\n".join([el for el, _
-                                            in self._unused_workspaces]))
+                          detail="\n".join([el for el in unused_workspaces]))
 
         # We set up two plans; one to track elements, the other to
         # build them once tracking has finished. The first plan
@@ -660,20 +657,18 @@ class Pipeline():
                 #
                 raise PipelineError("{}: {}".format(plugin, e), reason=e.reason) from e
 
-    # _initialize_workspaces()
+    # _collect_unused_workspaces()
     #
-    # Initialize active workspaces, and collect a list
-    # of any workspaces which are unused by the pipeline
+    # Collect a list of any workspaces which are unused by the pipeline
     #
-    def _initialize_workspaces(self):
-        for element_name, workspace in self.project.workspaces.list():
+    def _collect_unused_workspaces(self):
+        unused_workspaces = []
+        for element_name, _ in self.project.workspaces.list():
             for target in self.targets:
                 element = target.search(Scope.ALL, element_name)
-
                 if element is None:
-                    self._unused_workspaces.append((element_name, workspace))
-                else:
-                    workspace.init(element)
+                    unused_workspaces.append(element_name)
+        return unused_workspaces
 
     # _initialize_remote_caches()
     #
diff --git a/buildstream/_workspaces.py b/buildstream/_workspaces.py
index 7c8c516ad..6c8a7401b 100644
--- a/buildstream/_workspaces.py
+++ b/buildstream/_workspaces.py
@@ -51,9 +51,8 @@ class Workspace():
         self.path = path
         self.running_files = running_files if running_files is not None else {}
 
-        self._element = None
         self._project = project
-        self.__key = None
+        self._key = None
 
     @classmethod
     def from_yaml_node(cls, node, project):
@@ -76,30 +75,13 @@ class Workspace():
         return {key: val for key, val in self.__dict__.items()
                 if key in to_return and val is not None}
 
-    # open()
-    #
-    # "Open" this workspace, calling the init_workspace method of all
-    # its sources.
-    #
-    def open(self):
-        for source in self._element.sources():
-            source._init_workspace(self.path)
-
-    # init()
-    #
-    # Initialize the elements and sources associated to this
-    # workspace. Must be called before this object is used.
-    #
-    def init(self, element):
-        self._element = element
-
     # invalidate_key()
     #
     # Invalidate the workspace key, forcing a recalculation next time
     # it is accessed.
     #
     def invalidate_key(self):
-        self.__key = None
+        self._key = None
 
     # stage()
     #
@@ -109,7 +91,7 @@ class Workspace():
     #    directory (str) - The directory into which to stage this workspace
     #
     def stage(self, directory):
-        fullpath = os.path.join(self._project.directory, self.path)
+        fullpath = self.get_absolute_path()
         if os.path.isdir(fullpath):
             utils.copy_files(fullpath, directory)
         else:
@@ -122,16 +104,16 @@ class Workspace():
     # dependency. Duplicate files will be ignored.
     #
     # Args:
-    #     dep (Element) - The dependency whose files to append to
+    #     dep_name (str) - The dependency name whose files to append to
     #     files (str) - A list of files to append
     #
-    def add_running_files(self, dep, files):
-        if dep.name in self.running_files:
+    def add_running_files(self, dep_name, files):
+        if dep_name in self.running_files:
             # ruamel.py cannot serialize sets in python3.4
-            to_add = set(files) - set(self.running_files[dep.name])
-            self.running_files[dep.name].extend(to_add)
+            to_add = set(files) - set(self.running_files[dep_name])
+            self.running_files[dep_name].extend(to_add)
         else:
-            self.running_files[dep.name] = list(files)
+            self.running_files[dep_name] = list(files)
 
     # clear_running_files()
     #
@@ -164,8 +146,8 @@ class Workspace():
                                 "Failed loading workspace. Did you remove the "
                                 "workspace directory? {}".format(e))
 
-        if recalculate or self.__key is None:
-            fullpath = os.path.join(self._project.directory, self.path)
+        if recalculate or self._key is None:
+            fullpath = self.get_absolute_path()
 
             # Get a list of tuples of the the project relative paths and fullpaths
             if os.path.isdir(fullpath):
@@ -174,9 +156,9 @@ class Workspace():
             else:
                 filelist = [(self.path, fullpath)]
 
-            self.__key = [(relpath, unique_key(fullpath)) for relpath, fullpath in filelist]
+            self._key = [(relpath, unique_key(fullpath)) for relpath, fullpath in filelist]
 
-        return self.__key
+        return self._key
 
     # get_absolute_path():
     #
@@ -196,8 +178,7 @@ class Workspace():
 class Workspaces():
     def __init__(self, project):
         self._project = project
-        workspace_config = self._load_config()
-        self._workspaces = self._parse_workspace_config(workspace_config)
+        self._workspaces = self._load_config()
 
     # _list_workspaces()
     #
@@ -215,16 +196,15 @@ class Workspaces():
     # Create a workspace in the given path for the given element.
     #
     # Args:
-    #    element (Element) - The element for which to create a workspace
+    #    element_name (str) - The element name to create a workspace for
     #    path (str) - The path in which the workspace should be kept
     #
-    def create_workspace(self, element, path):
-        self._workspaces[element.name] = Workspace(path, self._project)
-        self._workspaces[element.name].init(element)
+    def create_workspace(self, element_name, path):
+        self._workspaces[element_name] = Workspace(path, self._project)
 
-        return self._workspaces[element.name]
+        return self._workspaces[element_name]
 
-    # _get_workspace()
+    # get_workspace()
     #
     # Get the path of the workspace source associated with the given
     # element's source at the given index
@@ -272,16 +252,12 @@ class Workspaces():
 
     # _load_config()
     #
-    # Load the workspace configuration and return a node containing
-    # all open workspaces for the project
+    # Loads and parses the workspace configuration
     #
     # Returns:
+    #    (dict) The extracted workspaces
     #
-    #    A node containing a dict that assigns elements to their
-    #    workspaces. For example:
-    #
-    #        alpha.bst: /home/me/alpha
-    #        bravo.bst: /home/me/bravo
+    # Raises: LoadError if there was a problem with the workspace config
     #
     def _load_config(self):
         workspace_file = os.path.join(self._project.directory, ".bst", "workspaces.yml")
@@ -294,7 +270,7 @@ class Workspaces():
 
             raise
 
-        return node
+        return self._parse_workspace_config(node)
 
     # _parse_workspace_config_format()
     #
diff --git a/buildstream/element.py b/buildstream/element.py
index 767860e54..4c7b96d51 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -518,7 +518,7 @@ class Element(Plugin):
                     # files, since removed files will be picked up by
                     # build systems anyway.
                     to_update, _, added = self.__artifacts.diff(dep, key_old, key_new, subdir='files')
-                    workspace.add_running_files(dep, to_update + added)
+                    workspace.add_running_files(dep.name, to_update + added)
                     project.workspaces.save_config()
                     to_update.extend(workspace.running_files[dep.name])
 
@@ -1350,6 +1350,20 @@ class Element(Plugin):
         os.makedirs(directory, exist_ok=True)
         return os.path.join(directory, logfile)
 
+    # _open_workspace():
+    #
+    # "Open" a workspace for this element
+    #
+    # This requires that a workspace already be created in
+    # the workspaces metadata first.
+    #
+    def _open_workspace(self):
+        workspace = self._get_workspace()
+        assert workspace is not None
+
+        for source in self.sources():
+            source._init_workspace(workspace.path)
+
     # _get_workspace():
     #
     # Returns: