full hash: fix uninstall and gc with full hash DB

The database now stores full hashes, so we need to adjust the criteria we use to
determine if something can be uninstalled. Specifically, it's ok to uninstall thing that
have remaining build-only dependents.

lib/spack/spack/cmd/uninstall.py

@@ -225,15 +225,25 @@ def do_uninstall(env, specs, force):
 
     # A package is ready to be uninstalled when nothing else references it,
     # unless we are requested to force uninstall it.
-    is_ready = lambda x: not spack.store.db.query_by_spec_hash(x)[1].ref_count
-    if force:
-        is_ready = lambda x: True
+    def is_ready(dag_hash):
+        if force:
+            return True
+
+        _, record = spack.store.db.query_by_spec_hash(dag_hash)
+        if not record.ref_count:
+            return True
+
+        # If this spec is only used as a build dependency, we can uninstall
+        return all(
+            dspec.deptypes == ("build",)
+            for dspec in record.spec.edges_from_dependents()
+        )
 
     while packages:
         ready = [x for x in packages if is_ready(x.spec.dag_hash())]
         if not ready:
             msg = 'unexpected error [cannot proceed uninstalling specs with' \
-                  ' remaining dependents {0}]'
+                  ' remaining link or run dependents {0}]'
             msg = msg.format(', '.join(x.name for x in packages))
             raise spack.error.SpackError(msg)
 

lib/spack/spack/database.py

@@ -691,6 +691,13 @@ def db_for_spec_hash(self, hash_key):
                 return db
 
     def query_by_spec_hash(self, hash_key, data=None):
+        """Get a spec for hash, and whether it's installed upstream.
+
+        Return:
+            (tuple): (bool, optional InstallRecord): bool tells us whether
+                the spec is installed upstream. Its InstallRecord is also
+                returned if it's installed at all; otherwise None.
+        """
         if data and hash_key in data:
             return False, data[hash_key]
         if not data:

lib/spack/spack/package.py

@@ -2371,7 +2371,11 @@ def uninstall_by_spec(spec, force=False, deprecator=None):
 
         if not force:
             dependents = spack.store.db.installed_relatives(
-                spec, 'parents', True)
+                spec,
+                direction='parents',
+                transitive=True,
+                deptype=("link", "run"),
+            )
             if dependents:
                 raise PackageStillNeededError(spec, dependents)