From 0e1d4c4bc71b90e5741026a60b980e040ae81429 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Wed, 1 Mar 2017 17:45:41 -0500
Subject: [PATCH] throw error in dev mode for missing bound properties (#249)

---
 src/generators/dom/index.js                   |  2 +-
 .../dom/visitors/attributes/binding/index.js  | 22 ++++++++++++-------
 .../_config.js                                |  7 ++++++
 .../main.html                                 |  1 +
 4 files changed, 23 insertions(+), 9 deletions(-)
 create mode 100644 test/generator/dev-warning-missing-data-binding/_config.js
 create mode 100644 test/generator/dev-warning-missing-data-binding/main.html

diff --git a/src/generators/dom/index.js b/src/generators/dom/index.js
index 2ca76ba096..05aab72394 100644
--- a/src/generators/dom/index.js
+++ b/src/generators/dom/index.js
@@ -319,7 +319,7 @@ export default function dom ( parsed, source, options, names ) {
 	if ( options.dev ) {
 		Object.keys( generator.expectedProperties ).forEach( prop => {
 			stateBlock.addLine(
-				`if ( !( '${prop}' in this._state ) ) throw new Error( "Component was created without expected data property 'foo'" );`
+				`if ( !( '${prop}' in this._state ) ) throw new Error( "Component was created without expected data property '${prop}'" );`
 			);
 		});
 	}
diff --git a/src/generators/dom/visitors/attributes/binding/index.js b/src/generators/dom/visitors/attributes/binding/index.js
index 4123f3ad7a..ff3c6ee847 100644
--- a/src/generators/dom/visitors/attributes/binding/index.js
+++ b/src/generators/dom/visitors/attributes/binding/index.js
@@ -63,7 +63,7 @@ export default function createBinding ( generator, node, attribute, current, loc
 
 		do {
 			if ( fragment.expression && fragment.context === prop ) {
-				if ( !isReference( fragment.expression  ) ) {
+				if ( !isReference( fragment.expression ) ) {
 					// TODO this should happen in prior validation step
 					throw new Error( `${prop} is read-only, it cannot be bound` );
 				}
@@ -72,6 +72,8 @@ export default function createBinding ( generator, node, attribute, current, loc
 			}
 		} while ( fragment = fragment.parent );
 
+		generator.expectedProperties[ prop ] = true;
+
 		const listName = current.listNames[ parts[0] ];
 		const indexName = current.indexNames[ parts[0] ];
 
@@ -84,14 +86,18 @@ export default function createBinding ( generator, node, attribute, current, loc
 
 			component._set({ ${prop}: component.get( '${prop}' ) });
 		`;
-	} else if ( deep ) {
-		setter = deindent`
-			var ${parts[0]} = component.get( '${parts[0]}' );
-			${parts[0]}.${parts.slice( 1 ).join( '.' )} = ${value};
-			component._set({ ${parts[0]}: ${parts[0]} });
-		`;
 	} else {
-		setter = `component._set({ ${attribute.value}: ${value} });`;
+		if ( deep ) {
+			setter = deindent`
+				var ${parts[0]} = component.get( '${parts[0]}' );
+				${parts[0]}.${parts.slice( 1 ).join( '.' )} = ${value};
+				component._set({ ${parts[0]}: ${parts[0]} });
+			`;
+		} else {
+			setter = `component._set({ ${attribute.value}: ${value} });`;
+		}
+
+		generator.expectedProperties[ parts[0] ] = true;
 	}
 
 	// special case
diff --git a/test/generator/dev-warning-missing-data-binding/_config.js b/test/generator/dev-warning-missing-data-binding/_config.js
new file mode 100644
index 0000000000..7b3e61fcda
--- /dev/null
+++ b/test/generator/dev-warning-missing-data-binding/_config.js
@@ -0,0 +1,7 @@
+export default {
+	dev: true,
+
+	error ( assert, err ) {
+		assert.equal( err.message, `Component was created without expected data property 'value'` );
+	}
+};
\ No newline at end of file
diff --git a/test/generator/dev-warning-missing-data-binding/main.html b/test/generator/dev-warning-missing-data-binding/main.html
new file mode 100644
index 0000000000..f24d608cd5
--- /dev/null
+++ b/test/generator/dev-warning-missing-data-binding/main.html
@@ -0,0 +1 @@
+<input bind:value>
\ No newline at end of file