fix(docker): move dedup helper to a model-free module (CI green)

The widget-dedup test imported plugins.docker.routes, which re-imports
plugins.docker.models after the app already loaded the docker plugin —
"Table 'docker_containers' is already defined". Same plugin-loader gotcha the
host_agent query helpers avoid.

Extract dedup_by_container_id into plugins/docker/dedup.py (imports no ORM
models, so it's safe to import in either environment); routes.py imports it
from there and the test targets the model-free module.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016Jg27rgypiW2efULXJDtMC

plugins/docker/dedup.py

@@ -0,0 +1,27 @@
+"""Model-free Docker view helpers.
+
+Kept separate from routes.py/models.py so tests can import it directly: importing
+a module that re-imports plugins.docker.models AFTER the app has loaded the docker
+plugin raises "Table 'docker_containers' is already defined". This module touches
+no ORM models, so it's safe to import in either environment.
+"""
+from __future__ import annotations
+
+
+def dedup_by_container_id(containers: list) -> list:
+    """Collapse containers double-reported across hosts. Swarm-aware agents on
+    every manager list cluster-wide tasks, so the same container (identical
+    container_id) arrives once per manager and would otherwise be counted N times.
+    Keep the first occurrence per non-empty container_id — callers order
+    running-first, so a running report wins over a stale stopped one. Rows without
+    a container_id (older agents) can't be matched, so they're kept as-is."""
+    seen: set[str] = set()
+    out = []
+    for c in containers:
+        cid = (c.container_id or "").strip()
+        if cid:
+            if cid in seen:
+                continue
+            seen.add(cid)
+        out.append(c)
+    return out

plugins/docker/routes.py

@@ -10,6 +10,7 @@ from steward.auth.middleware import require_role
 from steward.models.users import UserRole
 from steward.models.hosts import Host
 from steward.core.time_range import parse_range, DEFAULT_RANGE
+from .dedup import dedup_by_container_id
 from .models import (
     DockerContainer, DockerDiskUsage, DockerEvent, DockerImage, DockerMetric,
     DockerSwarmNode, DockerSwarmService,
@@ -205,25 +206,6 @@ async def rows():
     )
 
 
-def _dedup_by_container_id(containers: list) -> list:
-    """Collapse containers double-reported across hosts. Swarm-aware agents on
-    every manager list cluster-wide tasks, so the same container (identical
-    container_id) arrives once per manager and would otherwise be counted N times.
-    Keep the first occurrence per non-empty container_id — callers order
-    running-first, so a running report wins over a stale stopped one. Rows without
-    a container_id (older agents) can't be matched, so they're kept as-is."""
-    seen: set[str] = set()
-    out = []
-    for c in containers:
-        cid = (c.container_id or "").strip()
-        if cid:
-            if cid in seen:
-                continue
-            seen.add(cid)
-        out.append(c)
-    return out
-
-
 @docker_bp.get("/widget")
 @require_role(UserRole.viewer)
 async def widget():
@@ -233,7 +215,7 @@ async def widget():
     since_24h = datetime.now(timezone.utc) - timedelta(hours=24)
 
     async with current_app.db_sessionmaker() as db:
-        all_containers = _dedup_by_container_id(list((await db.execute(
+        all_containers = dedup_by_container_id(list((await db.execute(
             select(DockerContainer).order_by(
                 (DockerContainer.status == "running").desc(),
                 DockerContainer.name,
@@ -284,7 +266,7 @@ async def widget_resources():
     async with current_app.db_sessionmaker() as db:
         # Dedup before the limit, else swarm tasks reported by both managers can
         # fill the list with duplicates of the same container.
-        containers = _dedup_by_container_id(list((await db.execute(
+        containers = dedup_by_container_id(list((await db.execute(
             select(DockerContainer)
             .where(DockerContainer.status == "running")
             .order_by(DockerContainer.cpu_pct.desc().nullslast())

tests/integration/test_docker.py

@@ -456,14 +456,14 @@ def test_widget_dedup_collapses_cross_manager_duplicates():
     the dashboard widget must count it once. Older agents send no container_id,
     so those rows can't be matched and are all kept."""
     from types import SimpleNamespace
-    from plugins.docker.routes import _dedup_by_container_id
+    from plugins.docker.dedup import dedup_by_container_id
 
     def c(cid, name, status="running"):
         return SimpleNamespace(container_id=cid, name=name, status=status)
 
     rows = [c("abc", "web@m1"), c("abc", "web@m2"),  # same task, two managers
             c("def", "db"), c("", "noid-1"), c("", "noid-2")]
-    out = _dedup_by_container_id(rows)
+    out = dedup_by_container_id(rows)
 
     assert len(out) == 4                                       # one "abc" dropped
     abc = [r for r in out if r.container_id == "abc"]