fix: drop triggers on dropped tables before their functions (#505)

internal/diff/diff.go

@@ -2101,6 +2101,12 @@ func (d *ddlDiff) generateDropSQL(targetSchema string, collector *diffCollector,
 	generateDropTriggersFromModifiedTables(d.modifiedTables, targetSchema, collector)
 	generateDropTriggersFromModifiedViews(d.modifiedViews, targetSchema, collector, preDroppedViews)
 
+	// Drop triggers from tables and views that are themselves being dropped.
+	// This must happen before DROP FUNCTION so that trigger→function
+	// dependencies are removed first (#505).
+	generateDropTriggersFromDroppedTables(d.droppedTables, targetSchema, collector)
+	generateDropTriggersFromDroppedViews(d.droppedViews, targetSchema, collector, preDroppedViews)
+
 	// Drop aggregates before functions, since an aggregate depends on its
 	// transition/final functions (issue #416).
 	generateDropAggregatesSQL(d.droppedAggregates, targetSchema, collector)

internal/diff/trigger.go

@@ -234,6 +234,83 @@ func generateDropTriggersFromModifiedViews(views []*viewDiff, targetSchema strin
 	}
 }
 
+// generateDropTriggersFromDroppedTables emits DROP TRIGGER for all triggers on
+// tables that are being dropped. This must run before DROP FUNCTION so that
+// trigger→function dependencies are removed first (#505).
+func generateDropTriggersFromDroppedTables(tables []*ir.Table, targetSchema string, collector *diffCollector) {
+	var allTriggers []*ir.Trigger
+
+	for _, table := range tables {
+		for _, trigger := range table.Triggers {
+			allTriggers = append(allTriggers, trigger)
+		}
+	}
+
+	sort.Slice(allTriggers, func(i, j int) bool {
+		if allTriggers[i].Schema != allTriggers[j].Schema {
+			return allTriggers[i].Schema < allTriggers[j].Schema
+		}
+		if allTriggers[i].Table != allTriggers[j].Table {
+			return allTriggers[i].Table < allTriggers[j].Table
+		}
+		return allTriggers[i].Name < allTriggers[j].Name
+	})
+
+	for _, trigger := range allTriggers {
+		tableName := getTableNameWithSchema(trigger.Schema, trigger.Table, targetSchema)
+		sql := fmt.Sprintf("DROP TRIGGER IF EXISTS %s ON %s;", ir.QuoteIdentifier(trigger.Name), tableName)
+
+		context := &diffContext{
+			Type:                DiffTypeTableTrigger,
+			Operation:           DiffOperationDrop,
+			Path:                fmt.Sprintf("%s.%s.%s", trigger.Schema, trigger.Table, trigger.Name),
+			Source:              trigger,
+			CanRunInTransaction: true,
+		}
+		collector.collect(context, sql)
+	}
+}
+
+// generateDropTriggersFromDroppedViews emits DROP TRIGGER for all triggers on
+// views that are being dropped (same rationale as dropped tables, #505).
+func generateDropTriggersFromDroppedViews(views []*ir.View, targetSchema string, collector *diffCollector, preDroppedViews map[string]bool) {
+	var allTriggers []*ir.Trigger
+
+	for _, view := range views {
+		viewKey := view.Schema + "." + view.Name
+		if preDroppedViews != nil && preDroppedViews[viewKey] {
+			continue
+		}
+		for _, trigger := range view.Triggers {
+			allTriggers = append(allTriggers, trigger)
+		}
+	}
+
+	sort.Slice(allTriggers, func(i, j int) bool {
+		if allTriggers[i].Schema != allTriggers[j].Schema {
+			return allTriggers[i].Schema < allTriggers[j].Schema
+		}
+		if allTriggers[i].Table != allTriggers[j].Table {
+			return allTriggers[i].Table < allTriggers[j].Table
+		}
+		return allTriggers[i].Name < allTriggers[j].Name
+	})
+
+	for _, trigger := range allTriggers {
+		tableName := getTableNameWithSchema(trigger.Schema, trigger.Table, targetSchema)
+		sql := fmt.Sprintf("DROP TRIGGER IF EXISTS %s ON %s;", ir.QuoteIdentifier(trigger.Name), tableName)
+
+		context := &diffContext{
+			Type:                DiffTypeViewTrigger,
+			Operation:           DiffOperationDrop,
+			Path:                fmt.Sprintf("%s.%s.%s", trigger.Schema, trigger.Table, trigger.Name),
+			Source:              trigger,
+			CanRunInTransaction: true,
+		}
+		collector.collect(context, sql)
+	}
+}
+
 // generateTriggerSQLWithMode generates CREATE [OR REPLACE] TRIGGER or CREATE CONSTRAINT TRIGGER statement
 func generateTriggerSQLWithMode(trigger *ir.Trigger, targetSchema string, qualifySchema bool) string {
 	// Build event list in standard order: INSERT, UPDATE, DELETE, TRUNCATE

testdata/diff/dependency/issue_505_drop_trigger_function_with_table/diff.sql

@@ -0,0 +1,5 @@
+DROP TRIGGER IF EXISTS events_notify ON events;
+
+DROP FUNCTION IF EXISTS notify_event();
+
+DROP TABLE IF EXISTS events CASCADE;

testdata/diff/dependency/issue_505_drop_trigger_function_with_table/new.sql

@@ -0,0 +1 @@
+-- empty: drop everything

testdata/diff/dependency/issue_505_drop_trigger_function_with_table/old.sql

@@ -0,0 +1,20 @@
+CREATE TABLE events (
+    id serial PRIMARY KEY,
+    payload jsonb NOT NULL,
+    created_at timestamp DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE FUNCTION notify_event()
+RETURNS trigger
+LANGUAGE plpgsql
+AS $$
+BEGIN
+    PERFORM pg_notify('events', NEW.id::text);
+    RETURN NEW;
+END;
+$$;
+
+CREATE TRIGGER events_notify
+    AFTER INSERT ON events
+    FOR EACH ROW
+    EXECUTE FUNCTION notify_event();

testdata/diff/dependency/issue_505_drop_trigger_function_with_table/plan.json

@@ -0,0 +1,32 @@
+{
+  "version": "1.0.0",
+  "pgschema_version": "1.12.0",
+  "created_at": "1970-01-01T00:00:00Z",
+  "source_fingerprint": {
+    "hash": "b830414412e5c92476a85d494c5017028c5adcc5f7ead7b1322e85d7514349bc"
+  },
+  "groups": [
+    {
+      "steps": [
+        {
+          "sql": "DROP TRIGGER IF EXISTS events_notify ON events;",
+          "type": "table.trigger",
+          "operation": "drop",
+          "path": "public.events.events_notify"
+        },
+        {
+          "sql": "DROP FUNCTION IF EXISTS notify_event();",
+          "type": "function",
+          "operation": "drop",
+          "path": "public.notify_event"
+        },
+        {
+          "sql": "DROP TABLE IF EXISTS events CASCADE;",
+          "type": "table",
+          "operation": "drop",
+          "path": "public.events"
+        }
+      ]
+    }
+  ]
+}

testdata/diff/dependency/issue_505_drop_trigger_function_with_table/plan.sql

@@ -0,0 +1,5 @@
+DROP TRIGGER IF EXISTS events_notify ON events;
+
+DROP FUNCTION IF EXISTS notify_event();
+
+DROP TABLE IF EXISTS events CASCADE;

testdata/diff/dependency/issue_505_drop_trigger_function_with_table/plan.txt

@@ -0,0 +1,21 @@
+Plan: 2 to drop.
+
+Summary by type:
+  functions: 1 to drop
+  tables: 1 to drop
+
+Functions:
+  - notify_event
+
+Tables:
+  - events
+    - events_notify (trigger)
+
+DDL to be executed:
+--------------------------------------------------
+
+DROP TRIGGER IF EXISTS events_notify ON events;
+
+DROP FUNCTION IF EXISTS notify_event();
+
+DROP TABLE IF EXISTS events CASCADE;