validation: Require there be non-bootstrap chunks in systems

Bootstrap chunks don't make it into the final system, so there needs to
be an extra check for empty systems after the sources have been collected.

This was complicated slightly by the fact that if you try to build a chunk
directly you will have no strata in your sources, hence no non-bootstrap
chunks, but validation for having been told to build a chunk is best
handled later.

This amends the old yarns that depended on building a bootstrap chunk
and adds a new one that explicitly builds a system with bootstrap
chunks.

1 files changed, 40 insertions, 6 deletions

diff --git a/morphlib/buildcommand.py b/morphlib/buildcommand.py
index 8ad893a9..4b3b2108 100644
--- a/morphlib/buildcommand.py
+++ b/morphlib/buildcommand.py
@@ -49,8 +49,8 @@ class BuildCommand(object):
                             repo_name=repo_name, ref=ref, filename=filename)
             self.app.status(msg='Deciding on task order')
             srcpool = self.create_source_pool(repo_name, ref, filename)
+            self.validate_sources(srcpool)
             root_artifact = self.resolve_artifacts(srcpool)
-            self._validate_architecture(root_artifact)
             self.build_in_order(root_artifact)
 
         self.app.status(msg='Build ends successfully')
@@ -83,11 +83,27 @@ class BuildCommand(object):
         srcpool = self.app.create_source_pool(
             self.lrc, self.rrc, (repo_name, ref, filename))
 
+        return srcpool
+
+    def validate_sources(self, srcpool):
         self.app.status(
             msg='Validating cross-morphology references', chatty=True)
         self._validate_cross_morphology_references(srcpool)
 
-        return srcpool
+        self.app.status(msg='Validating for there being non-bootstrap chunks',
+                        chatty=True)
+        self._validate_has_non_bootstrap_chunks(srcpool)
+
+    def _validate_root_artifact(self, root_artifact):
+        self._validate_root_kind(root_artifact)
+        self._validate_architecture(root_artifact)
+
+    @staticmethod
+    def _validate_root_kind(root_artifact):
+        root_kind = root_artifact.source.morphology['kind']
+        if root_kind != 'system':
+            raise morphlib.Error(
+                'Building a %s directly is not supported' % root_kind)
 
     def _validate_architecture(self, root_artifact):
         '''Perform the validation between root and target architectures.'''
@@ -100,6 +116,22 @@ class BuildCommand(object):
                     'Host architecture is %s but target is %s'
                     % (host_arch, root_arch))
 
+    @staticmethod
+    def _validate_has_non_bootstrap_chunks(srcpool):
+        stratum_sources = [src for src in srcpool
+                           if src.morphology['kind'] == 'stratum']
+        # any will return true for an empty iterable, which will give
+        # a false positive when there are no strata.
+        # This is an error by itself, but the source of this error can
+        # be better diagnosed later, so we abort validating here.
+        if not stratum_sources:
+            return
+
+        if not any(spec.get('build-mode', 'staging') != 'bootstrap'
+                   for src in stratum_sources
+                   for spec in src.morphology['chunks']):
+            raise morphlib.Error('No non-bootstrap chunks found.')
+
     def resolve_artifacts(self, srcpool):
         '''Resolve the artifacts that will be built for a set of sources'''
 
@@ -112,10 +144,12 @@ class BuildCommand(object):
         self.app.status(msg='Computing build order', chatty=True)
         root_artifact = self._find_root_artifact(artifacts)
 
-        root_kind = root_artifact.source.morphology['kind']
-        if root_kind != 'system':
-            raise morphlib.Error(
-                'Building a %s directly is not supported' % root_kind)
+        # Validate the root artifact here, since it's a costly function
+        # to finalise it, so any pre finalisation validation is better
+        # done before that happens, but we also don't want to expose
+        # the root artifact until it's finalised.
+        self.app.status(msg='Validating root artifact', chatty=True)
+        self._validate_root_artifact(root_artifact)
         arch = root_artifact.source.morphology['arch']
 
         self.app.status(msg='Creating build environment for %(arch)s',