Make a partly-undone import retryable, and refuse a plan it cannot deliver

scripts/site_imports/approval.py

@@ -57,7 +57,7 @@ def plan_hash(plan):
     return hasher.hexdigest()
 
 
-def build_packet(kind, plan, counts, groups):
+def build_packet(kind, plan, counts, groups, creatable=None):
     """Build an approval packet from a plan.
 
     kind    a short label identifying the importer, stored on the packet.
@@ -69,6 +69,12 @@ def build_packet(kind, plan, counts, groups):
             column is what a human would act on - the raw export value for
             UNRESOLVED (so they know what to alias) and the canonical name for
             NEEDS_CREATE (so they know what would be created).
+    creatable
+            the group names the caller's writer can actually create, or None
+            for "no opinion". A needs-create group outside this set is reported
+            under `uncreatable` and makes the packet blocking, because a plan
+            that promises rows nothing will create is as unrunnable as one with
+            unresolved values.
 
     needscreate is keyed on the canonical name column when present; callers pass
     the *_name column for that via the fourth tuple element when it differs from
@@ -86,6 +92,26 @@ def build_packet(kind, plan, counts, groups):
         if needs_hits:
             needscreate[group_name] = needs_hits
 
+    # A needs-create group the writer cannot actually create BLOCKS the plan,
+    # the same as an unresolved value. It is the same failure either way: the
+    # import cannot do what the preview says it would.
+    #
+    # It has to be decided HERE rather than at write time. The writer's own
+    # refusal sits behind the acknowledgement check, and the UI only ever
+    # acknowledges the groups it renders a control for - so a plan needing an
+    # uncreatable group reached Commit looking clean, and died on a message
+    # about acknowledging something the screen had no checkbox for. Blocking at
+    # plan time puts it in the preview, where the admin can act on it.
+    #
+    # creatable=None means "no opinion" - the CLI callers that do not pass it
+    # keep the old behaviour.
+    uncreatable = OrderedDict()
+    if creatable is not None:
+        allowed = set(creatable)
+        for group_name, hits in needscreate.items():
+            if group_name not in allowed:
+                uncreatable[group_name] = hits
+
     return OrderedDict([
         ('kind', kind),
         ('batchid', str(uuid.uuid4())),
@@ -93,8 +119,9 @@ def build_packet(kind, plan, counts, groups):
         ('rowcount', len(plan)),
         ('counts', OrderedDict(counts)),
         ('needscreate', needscreate),
+        ('uncreatable', uncreatable),
         ('unresolved', unresolved),
-        ('blocking', bool(unresolved)),
+        ('blocking', bool(unresolved) or bool(uncreatable)),
     ])
 
 
@@ -123,6 +150,20 @@ def format_packet(packet):
                 lines.append('    + %-28s (%d rows)' % (name, count))
             lines.append('    total new %s rows: %d' % (group, total))
 
+    # An uncreatable group blocks, so it has to be ON SCREEN. Setting
+    # blocking without printing the reason left "BLOCKED (resolve the values
+    # above)" pointing at nothing.
+    uncreatable = packet.get('uncreatable') or {}
+    if uncreatable:
+        for group, items in uncreatable.items():
+            lines.append('')
+            lines.append('  BLOCKING: this import cannot create %s rows, but '
+                         '%d are needed - create them first, or alias the '
+                         'export values to rows that exist:'
+                         % (group, len(items)))
+            for name, count in items.items():
+                lines.append('    x %-28s (%d rows)' % (name, count))
+
     unresolved = packet.get('unresolved') or {}
     if unresolved:
         for group, items in unresolved.items():
@@ -134,7 +175,7 @@ def format_packet(packet):
 
     lines.append('')
     lines.append('  status   : %s' % (
-        'BLOCKED (resolve the values above)' if packet.get('blocking')
+        'BLOCKED (resolve the problems above)' if packet.get('blocking')
         else 'READY for acknowledgment'))
     return '\n'.join(lines)