_pipeline.py, loader.py: Move Element._preflight() to new_from_meta()

It's essential to call preflight() when loading/resolving the Elements.
This patch moves the preflight call to new_from_meta, so that it is
called as soon as the Element is created. This avoids the need for
having multiple callsites.

4 files changed, 45 insertions, 50 deletions

diff --git a/src/buildstream/_loader/loader.py b/src/buildstream/_loader/loader.py
index 5a2624c6a..207de9adb 100644
--- a/src/buildstream/_loader/loader.py
+++ b/src/buildstream/_loader/loader.py
@@ -604,7 +604,6 @@ class Loader():
                                 provenance_str, filename, meta_element.kind))
 
         element = Element._new_from_meta(meta_element)
-        element._preflight()
         element._update_state()
 
         # If this junction element points to a sub-sub-project, we need to
diff --git a/src/buildstream/_pipeline.py b/src/buildstream/_pipeline.py
index 440bd8bd3..a96a3f731 100644
--- a/src/buildstream/_pipeline.py
+++ b/src/buildstream/_pipeline.py
@@ -125,10 +125,6 @@ class Pipeline():
     def resolve_elements(self, targets):
         with self._context.messenger.timed_activity("Resolving cached state", silent_nested=True):
             for element in self.dependencies(targets, Scope.ALL):
-
-                # Preflight
-                element._preflight()
-
                 # Determine initial element state.
                 element._update_state()
 
diff --git a/src/buildstream/element.py b/src/buildstream/element.py
index 570e473e9..1451be9b9 100644
--- a/src/buildstream/element.py
+++ b/src/buildstream/element.py
@@ -969,6 +969,8 @@ class Element(Plugin):
             dependency.__reverse_build_deps.add(element)
         element.__remaining_build_deps_uncached = len(element.__build_dependencies)
 
+        element.__preflight()
+
         return element
 
     # _clear_meta_elements_cache()
@@ -1226,49 +1228,6 @@ class Element(Plugin):
         _, display_key, _ = self._get_display_key()
         return display_key
 
-    # _preflight():
-    #
-    # A wrapper for calling the abstract preflight() method on
-    # the element and its sources.
-    #
-    def _preflight(self):
-
-        if self.BST_FORBID_RDEPENDS and self.BST_FORBID_BDEPENDS:
-            if any(self.dependencies(Scope.RUN, recurse=False)) or any(self.dependencies(Scope.BUILD, recurse=False)):
-                raise ElementError("{}: Dependencies are forbidden for '{}' elements"
-                                   .format(self, self.get_kind()), reason="element-forbidden-depends")
-
-        if self.BST_FORBID_RDEPENDS:
-            if any(self.dependencies(Scope.RUN, recurse=False)):
-                raise ElementError("{}: Runtime dependencies are forbidden for '{}' elements"
-                                   .format(self, self.get_kind()), reason="element-forbidden-rdepends")
-
-        if self.BST_FORBID_BDEPENDS:
-            if any(self.dependencies(Scope.BUILD, recurse=False)):
-                raise ElementError("{}: Build dependencies are forbidden for '{}' elements"
-                                   .format(self, self.get_kind()), reason="element-forbidden-bdepends")
-
-        if self.BST_FORBID_SOURCES:
-            if any(self.sources()):
-                raise ElementError("{}: Sources are forbidden for '{}' elements"
-                                   .format(self, self.get_kind()), reason="element-forbidden-sources")
-
-        try:
-            self.preflight()
-        except BstError as e:
-            # Prepend provenance to the error
-            raise ElementError("{}: {}".format(self, e), reason=e.reason, detail=e.detail) from e
-
-        # Ensure that the first source does not need access to previous soruces
-        if self.__sources and self.__sources[0]._requires_previous_sources():
-            raise ElementError("{}: {} cannot be the first source of an element "
-                               "as it requires access to previous sources"
-                               .format(self, self.__sources[0]))
-
-        # Preflight the sources
-        for source in self.sources():
-            source._preflight()
-
     # _schedule_tracking():
     #
     # Force an element state to be inconsistent. Any sources appear to be
@@ -2370,6 +2329,49 @@ class Element(Plugin):
                 # have been executed.
                 sandbox._callback(mark_workspace_prepared)
 
+    # __preflight():
+    #
+    # A internal wrapper for calling the abstract preflight() method on
+    # the element and its sources.
+    #
+    def __preflight(self):
+
+        if self.BST_FORBID_RDEPENDS and self.BST_FORBID_BDEPENDS:
+            if any(self.dependencies(Scope.RUN, recurse=False)) or any(self.dependencies(Scope.BUILD, recurse=False)):
+                raise ElementError("{}: Dependencies are forbidden for '{}' elements"
+                                   .format(self, self.get_kind()), reason="element-forbidden-depends")
+
+        if self.BST_FORBID_RDEPENDS:
+            if any(self.dependencies(Scope.RUN, recurse=False)):
+                raise ElementError("{}: Runtime dependencies are forbidden for '{}' elements"
+                                   .format(self, self.get_kind()), reason="element-forbidden-rdepends")
+
+        if self.BST_FORBID_BDEPENDS:
+            if any(self.dependencies(Scope.BUILD, recurse=False)):
+                raise ElementError("{}: Build dependencies are forbidden for '{}' elements"
+                                   .format(self, self.get_kind()), reason="element-forbidden-bdepends")
+
+        if self.BST_FORBID_SOURCES:
+            if any(self.sources()):
+                raise ElementError("{}: Sources are forbidden for '{}' elements"
+                                   .format(self, self.get_kind()), reason="element-forbidden-sources")
+
+        try:
+            self.preflight()
+        except BstError as e:
+            # Prepend provenance to the error
+            raise ElementError("{}: {}".format(self, e), reason=e.reason, detail=e.detail) from e
+
+        # Ensure that the first source does not need access to previous soruces
+        if self.__sources and self.__sources[0]._requires_previous_sources():
+            raise ElementError("{}: {} cannot be the first source of an element "
+                               "as it requires access to previous sources"
+                               .format(self, self.__sources[0]))
+
+        # Preflight the sources
+        for source in self.sources():
+            source._preflight()
+
     # __assert_cached()
     #
     # Raises an error if the artifact is not cached.
diff --git a/tests/artifactcache/push.py b/tests/artifactcache/push.py
index 9b976c490..da658f76b 100644
--- a/tests/artifactcache/push.py
+++ b/tests/artifactcache/push.py
@@ -124,8 +124,6 @@ def _test_push(user_config_file, project_dir, element_name, queue):
     # This is duplicated from Pipeline.resolve_elements()
     # as this test does not use the cli frontend.
     for e in element.dependencies(Scope.ALL):
-        # Preflight
-        e._preflight()
         # Determine initial element state.
         e._update_state()