From c1b1e4b18821cc035fec975c1c04cd57b6a834cb Mon Sep 17 00:00:00 2001
From: ekhaled <me.khaled@gmail.com>
Date: Fri, 30 Mar 2018 20:09:19 +0100
Subject: [PATCH] add dev mode warning when teardown is returned instead of
 destroy

---
 src/generators/nodes/Element.ts                  |  8 ++++++++
 .../_config.js                                   |  7 +++++++
 .../main.html                                    | 16 ++++++++++++++++
 3 files changed, 31 insertions(+)
 create mode 100644 test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/_config.js
 create mode 100644 test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/main.html

diff --git a/src/generators/nodes/Element.ts b/src/generators/nodes/Element.ts
index 1d4f9fdf53..a43c725ff4 100644
--- a/src/generators/nodes/Element.ts
+++ b/src/generators/nodes/Element.ts
@@ -516,6 +516,14 @@ export default class Element extends Node {
 					});
 				`);
 
+				if (generator.options.dev) {
+					block.builders.hydrate.addBlock(deindent`
+						if (${handlerName}.teardown) {
+							console.warn("Return 'destroy()' from custom event handlers. Returning 'teardown()' has been deprecated and will be unsupported in Svelte 2");
+						}
+					`);
+				}
+
 				block.builders.destroy.addLine(deindent`
 					${handlerName}[${handlerName}.destroy ? 'destroy' : 'teardown']();
 				`);
diff --git a/test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/_config.js b/test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/_config.js
new file mode 100644
index 0000000000..59c583ba1a
--- /dev/null
+++ b/test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/_config.js
@@ -0,0 +1,7 @@
+export default {
+	dev: true,
+
+	warnings: [
+		`Return 'destroy()' from custom event handlers. Returning 'teardown()' has been deprecated and will be unsupported in Svelte 2`
+	]
+};
\ No newline at end of file
diff --git a/test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/main.html b/test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/main.html
new file mode 100644
index 0000000000..1e83835f03
--- /dev/null
+++ b/test/runtime/samples/dev-warning-custom-event-destroy-not-teardown/main.html
@@ -0,0 +1,16 @@
+<button on:foo='foo()'>foo</button>
+
+<script>
+	export default {
+		methods: {
+			foo() {}
+		},
+		events: {
+			foo(node, callback) {
+				return {
+					teardown() {}
+				}
+			}
+		}
+	};
+</script>
\ No newline at end of file