fix(dashboard): resolve [object Object] in ui-text widgets + use dispatcher pattern

FlowFuse ui-text only supports {{msg.payload}} — not nested paths
like {{msg.payload.state}}. Every ui-text was showing [object Object]
because the formatter sent a fat object as msg.payload and the format
template tried to access sub-fields.

Fix: per-pump (and per-MGC, per-PS) "dispatcher" function on the
Dashboard UI tab. The dispatcher receives the fat object via one
link-in, then returns 7-9 plain-string outputs — one per ui-text
widget — each with msg.payload set to the formatted string value.
Outputs 8+9 carry numeric values (flowNum/powerNum) tagged with
msg.topic for the trend charts, wired directly to both short-term
and long-term chart nodes.

Pattern documented as the recommended approach in the rule set:
"FlowFuse ui-text receives plain strings only — use a dispatcher
function to split a fat object into per-widget outputs."

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/pumpingstation-3pumps-dashboard/build_flow.py

@@ -402,8 +402,9 @@ def build_process_tab():
             ],
         })
 
-        # Per-pump output formatter: builds the structured event used by the
-        # dashboard widgets and trend feeders.
+        # Per-pump output formatter: builds a fat object with all fields.
+        # The dashboard dispatcher (on the UI tab) then splits it into
+        # plain-string payloads per ui-text widget. One link-out per pump.
         nodes.append(function_node(
             f"format_{pump}", TAB_PROCESS, LANE_X[4], y_section + 80,
             f"format {label} port 0",
@@ -423,18 +424,18 @@ def build_process_tab():
             "  state: c.state || 'idle',\n"
             "  mode:  c.mode  || 'auto',\n"
             "  ctrl:  c.ctrl != null ? Number(c.ctrl).toFixed(1) + '%' : 'n/a',\n"
-            "  flow:  flow != null ? Number(flow).toFixed(1) + ' m³/h' : 'n/a',\n"
+            "  flow:  flow  != null ? Number(flow).toFixed(1) + ' m³/h' : 'n/a',\n"
             "  power: power != null ? Number(power).toFixed(2) + ' kW' : 'n/a',\n"
-            "  pUp:   pU != null ? Number(pU).toFixed(0) : 'n/a',\n"
-            "  pDn:   pD != null ? Number(pD).toFixed(0) : 'n/a',\n"
-            "  flowNum:  flow != null ? Number(flow) : null,\n"
+            "  pUp:   pU != null ? Number(pU).toFixed(0) + ' mbar' : 'n/a',\n"
+            "  pDn:   pD != null ? Number(pD).toFixed(0) + ' mbar' : 'n/a',\n"
+            "  flowNum:  flow  != null ? Number(flow)  : null,\n"
             "  powerNum: power != null ? Number(power) : null,\n"
             "};\n"
             "return msg;",
             outputs=1, wires=[[f"lout_evt_{pump}"]],
         ))
 
-        # link-out: per-pump event stream → dashboard
+        # link-out: one per pump → dashboard dispatcher
         nodes.append(link_out(
             f"lout_evt_{pump}", TAB_PROCESS, LANE_X[5], y_section + 80,
             CH_PUMP_EVT[pump],
@@ -797,30 +798,56 @@ def build_ui_tab():
     nodes.append(link_in(
         "lin_evt_mgc_dash", TAB_UI, LANE_X[0], y + 40,
         CH_MGC_EVT, source_out_ids=["lout_evt_mgc"],
-        downstream=["ui_mgc_total_flow", "ui_mgc_total_power", "ui_mgc_eff"]
+        downstream=["dispatch_mgc"]
+    ))
+    nodes.append(function_node(
+        "dispatch_mgc", TAB_UI, LANE_X[1], y + 40,
+        "dispatch MGC",
+        "const p = msg.payload || {};\n"
+        "return [\n"
+        "  {payload: String(p.totalFlow  || 'n/a')},\n"
+        "  {payload: String(p.totalPower || 'n/a')},\n"
+        "  {payload: String(p.efficiency || 'n/a')},\n"
+        "];",
+        outputs=3,
+        wires=[["ui_mgc_total_flow"], ["ui_mgc_total_power"], ["ui_mgc_eff"]],
     ))
     nodes.append(ui_text("ui_mgc_total_flow",  TAB_UI, LANE_X[2], y + 40, g_mgc,
-                        "MGC total flow", "Total flow",  "{{msg.payload.totalFlow}}"))
+                        "MGC total flow", "Total flow",  "{{msg.payload}}"))
     nodes.append(ui_text("ui_mgc_total_power", TAB_UI, LANE_X[2], y + 70, g_mgc,
-                        "MGC total power", "Total power", "{{msg.payload.totalPower}}"))
+                        "MGC total power", "Total power", "{{msg.payload}}"))
     nodes.append(ui_text("ui_mgc_eff",         TAB_UI, LANE_X[2], y + 100, g_mgc,
-                        "MGC efficiency", "Group efficiency", "{{msg.payload.efficiency}}"))
+                        "MGC efficiency", "Group efficiency", "{{msg.payload}}"))
 
     nodes.append(link_in(
         "lin_evt_ps_dash", TAB_UI, LANE_X[0], y + 160,
         CH_PS_EVT, source_out_ids=["lout_evt_ps"],
-        downstream=["ui_ps_state", "ui_ps_level", "ui_ps_volume", "ui_ps_qin", "ui_ps_qout"]
+        downstream=["dispatch_ps"]
+    ))
+    nodes.append(function_node(
+        "dispatch_ps", TAB_UI, LANE_X[1], y + 160,
+        "dispatch PS",
+        "const p = msg.payload || {};\n"
+        "return [\n"
+        "  {payload: String(p.state  || 'idle')},\n"
+        "  {payload: String(p.level  || 'n/a')},\n"
+        "  {payload: String(p.volume || 'n/a')},\n"
+        "  {payload: String(p.qIn    || 'n/a')},\n"
+        "  {payload: String(p.qOut   || 'n/a')},\n"
+        "];",
+        outputs=5,
+        wires=[["ui_ps_state"], ["ui_ps_level"], ["ui_ps_volume"], ["ui_ps_qin"], ["ui_ps_qout"]],
     ))
     nodes.append(ui_text("ui_ps_state",  TAB_UI, LANE_X[2], y + 160, g_ps,
-                        "PS state", "Basin state",  "{{msg.payload.state}}"))
-    nodes.append(ui_text("ui_ps_level",  TAB_UI, LANE_X[2], y + 190, g_ps,
-                        "PS level", "Basin level",  "{{msg.payload.level}}"))
-    nodes.append(ui_text("ui_ps_volume", TAB_UI, LANE_X[2], y + 220, g_ps,
-                        "PS volume","Basin volume", "{{msg.payload.volume}}"))
-    nodes.append(ui_text("ui_ps_qin",    TAB_UI, LANE_X[2], y + 250, g_ps,
-                        "PS Qin",   "Inflow",       "{{msg.payload.qIn}}"))
-    nodes.append(ui_text("ui_ps_qout",   TAB_UI, LANE_X[2], y + 280, g_ps,
-                        "PS Qout",  "Pumped out",   "{{msg.payload.qOut}}"))
+                        "PS state", "Basin state",  "{{msg.payload}}"))
+    nodes.append(ui_text("ui_ps_level",  TAB_UI, LANE_X[2], y + 200, g_ps,
+                        "PS level", "Basin level",  "{{msg.payload}}"))
+    nodes.append(ui_text("ui_ps_volume", TAB_UI, LANE_X[2], y + 240, g_ps,
+                        "PS volume","Basin volume", "{{msg.payload}}"))
+    nodes.append(ui_text("ui_ps_qin",    TAB_UI, LANE_X[2], y + 280, g_ps,
+                        "PS Qin",   "Inflow",       "{{msg.payload}}"))
+    nodes.append(ui_text("ui_ps_qout",   TAB_UI, LANE_X[2], y + 320, g_ps,
+                        "PS Qout",  "Pumped out",   "{{msg.payload}}"))
 
     # ===== SECTION: Per-pump panels =====
     y_pumps_start = 1000
@@ -832,36 +859,54 @@ def build_ui_tab():
         nodes.append(comment(f"c_ui_{pump}", TAB_UI, LANE_X[2], y_p,
             f"── {label} ──", ""))
 
-        # link-in for this pump's events
+        # link-in: one fat object per pump → dispatcher splits into
+        # plain-string payloads per ui-text widget + numeric payloads
+        # for trend charts. 9 outputs total.
+        DISPLAY_FIELDS = [
+            ("State",        "state"),
+            ("Mode",         "mode"),
+            ("Controller %", "ctrl"),
+            ("Flow",         "flow"),
+            ("Power",        "power"),
+            ("p Upstream",   "pUp"),
+            ("p Downstream", "pDn"),
+        ]
         nodes.append(link_in(
             f"lin_evt_{pump}_dash", TAB_UI, LANE_X[0], y_p + 40,
             CH_PUMP_EVT[pump], source_out_ids=[f"lout_evt_{pump}"],
-            downstream=[
-                f"ui_{pump}_state",
-                f"ui_{pump}_mode",
-                f"ui_{pump}_ctrl",
-                f"ui_{pump}_flow",
-                f"ui_{pump}_power",
-                f"ui_{pump}_pUp",
-                f"ui_{pump}_pDn",
-                f"trend_split_{pump}",
+            downstream=[f"dispatch_{pump}"],
+        ))
+        # Dispatcher: takes the fat object and returns 9 outputs, each
+        # with a plain payload ready for a ui-text or trend chart.
+        nodes.append(function_node(
+            f"dispatch_{pump}", TAB_UI, LANE_X[1], y_p + 40,
+            f"dispatch {label}",
+            "const p = msg.payload || {};\n"
+            "return [\n"
+            "  {payload: String(p.state  || 'idle')},\n"
+            "  {payload: String(p.mode   || 'auto')},\n"
+            "  {payload: String(p.ctrl   || 'n/a')},\n"
+            "  {payload: String(p.flow   || 'n/a')},\n"
+            "  {payload: String(p.power  || 'n/a')},\n"
+            "  {payload: String(p.pUp    || 'n/a')},\n"
+            "  {payload: String(p.pDn    || 'n/a')},\n"
+            "  p.flowNum  != null ? {topic: '" + label + "', payload: p.flowNum}  : null,\n"
+            "  p.powerNum != null ? {topic: '" + label + "', payload: p.powerNum} : null,\n"
+            "];",
+            outputs=9,
+            wires=[
+                [f"ui_{pump}_{f}"] for _, f in DISPLAY_FIELDS
+            ] + [
+                ["trend_short_flow", "trend_long_flow"],       # output 7: flowNum → both flow charts
+                ["trend_short_power", "trend_long_power"],     # output 8: powerNum → both power charts
             ],
         ))
-
-        # Status text widgets — text-only, fed by the link-in
-        for k, (label_txt, fmt_field) in enumerate([
-            ("State",       "state"),
-            ("Mode",        "mode"),
-            ("Controller %", "ctrl"),
-            ("Flow",        "flow"),
-            ("Power",       "power"),
-            ("p Upstream",  "pUp"),
-            ("p Downstream", "pDn"),
-        ]):
+        # ui-text widgets
+        for k, (label_txt, field) in enumerate(DISPLAY_FIELDS):
             nodes.append(ui_text(
-                f"ui_{pump}_{fmt_field}", TAB_UI, LANE_X[2], y_p + 40 + k * 30, g,
+                f"ui_{pump}_{field}", TAB_UI, LANE_X[2], y_p + 40 + k * 40, g,
                 f"{label} {label_txt}", label_txt,
-                "{{msg.payload." + fmt_field + "}}"
+                "{{msg.payload}}"  # plain string — FlowFuse-safe
             ))
 
         # Setpoint slider → wrapper → link-out → process pump (cmd:setpoint-X)
@@ -914,23 +959,8 @@ def build_ui_tab():
             target_in_ids=[f"lin_seq_{pump}"]
         ))
 
-        # Trend feeder — 2 outputs (flow / power), each wired to BOTH
-        # the short-term and long-term chart on their respective pages.
-        nodes.append(function_node(
-            f"trend_split_{pump}", TAB_UI, LANE_X[3], y_p + 80,
-            f"trend split ({label})",
-            "const p = msg.payload || {};\n"
-            "const flowMsg  = p.flowNum  != null ? "
-            "{ topic: '" + label + "', payload: Number(p.flowNum) }  : null;\n"
-            "const powerMsg = p.powerNum != null ? "
-            "{ topic: '" + label + "', payload: Number(p.powerNum) } : null;\n"
-            "return [flowMsg, powerMsg];",
-            outputs=2,
-            wires=[
-                ["trend_short_flow", "trend_long_flow"],
-                ["trend_short_power", "trend_long_power"],
-            ]
-        ))
+        # (Trend feed is handled by dispatcher outputs 7+8 above — no separate
+        # trend_split function needed.)
 
     # ===== Trend charts — two pages, two charts per page =====
     # Short-term (10 min rolling window) and long-term (1 hour).