From 11e613e7d04c74cf54df098bf485644a7d287e2a Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Wed, 1 Feb 2017 17:16:15 -0500
Subject: [PATCH] handle default paramters in computed values (fixes #274)

---
 src/generators/Generator.js                              | 2 +-
 src/generators/dom/index.js                              | 8 ++++----
 test/generator/computed-values-default/_config.js        | 9 +++++++++
 test/generator/computed-values-default/main.html         | 9 +++++++++
 test/generator/computed-values/_config.js                | 1 +
 .../errors.json                                          | 0
 .../input.html                                           | 0
 7 files changed, 24 insertions(+), 5 deletions(-)
 create mode 100644 test/generator/computed-values-default/_config.js
 create mode 100644 test/generator/computed-values-default/main.html
 rename test/validator/{computed-values => properties-computed-values-needs-arguments}/errors.json (100%)
 rename test/validator/{computed-values => properties-computed-values-needs-arguments}/input.html (100%)

diff --git a/src/generators/Generator.js b/src/generators/Generator.js
index 84bd2be36758..8568a515e7e8 100644
--- a/src/generators/Generator.js
+++ b/src/generators/Generator.js
@@ -246,7 +246,7 @@ export default class Generator {
 					const key = prop.key.name;
 					const value = prop.value;
 
-					const deps = value.params.map( param => param.name );
+					const deps = value.params.map( param => param.type === 'AssignmentPattern' ? param.left.name : param.name );
 					dependencies.set( key, deps );
 				});
 
diff --git a/src/generators/dom/index.js b/src/generators/dom/index.js
index 649252557d05..41d95bb58421 100644
--- a/src/generators/dom/index.js
+++ b/src/generators/dom/index.js
@@ -185,19 +185,19 @@ export default function dom ( parsed, source, options, names ) {
 
 		computations.forEach( ({ key, deps }) => {
 			builder.addBlock( deindent`
-				if ( ${deps.map( dep => `( '${dep}' in newState && typeof state.${dep} === 'object' || state.${dep} !== oldState.${dep} )` ).join( ' || ' )} ) {
+				if ( isInitial || ${deps.map( dep => `( '${dep}' in newState && typeof state.${dep} === 'object' || state.${dep} !== oldState.${dep} )` ).join( ' || ' )} ) {
 					state.${key} = newState.${key} = template.computed.${key}( ${deps.map( dep => `state.${dep}` ).join( ', ' )} );
 				}
 			` );
 		});
 
 		builders.main.addBlock( deindent`
-			function applyComputations ( state, newState, oldState ) {
+			function applyComputations ( state, newState, oldState, isInitial ) {
 				${builder}
 			}
 		` );
 
-		builders._set.addLine( `applyComputations( this._state, newState, oldState )` );
+		builders._set.addLine( `applyComputations( this._state, newState, oldState, false )` );
 	}
 
 	// TODO is the `if` necessary?
@@ -277,7 +277,7 @@ export default function dom ( parsed, source, options, names ) {
 		function ${name} ( options ) {
 			options = options || {};
 			${generator.usesRefs ? `\nthis.refs = {}` : ``}
-			this._state = ${initialState};${templateProperties.computed ? `\napplyComputations( this._state, this._state, {} );` : ``}
+			this._state = ${initialState};${templateProperties.computed ? `\napplyComputations( this._state, this._state, {}, true );` : ``}
 
 			this._observers = {
 				pre: Object.create( null ),
diff --git a/test/generator/computed-values-default/_config.js b/test/generator/computed-values-default/_config.js
new file mode 100644
index 000000000000..9d761d891577
--- /dev/null
+++ b/test/generator/computed-values-default/_config.js
@@ -0,0 +1,9 @@
+export default {
+	html: '<p>2</p>',
+
+	test ( assert, component, target ) {
+		component.set({ a: 2 });
+		assert.equal( target.innerHTML, '<p>4</p>' );
+		component.teardown();
+	}
+};
diff --git a/test/generator/computed-values-default/main.html b/test/generator/computed-values-default/main.html
new file mode 100644
index 000000000000..74292a3a2e14
--- /dev/null
+++ b/test/generator/computed-values-default/main.html
@@ -0,0 +1,9 @@
+<p>{{foo}}</p>
+
+<script>
+	export default {
+		computed: {
+			foo: ( a = 1 ) => a * 2
+		}
+	};
+</script>
diff --git a/test/generator/computed-values/_config.js b/test/generator/computed-values/_config.js
index 179ebc2c9e47..b5f7112fa8e9 100644
--- a/test/generator/computed-values/_config.js
+++ b/test/generator/computed-values/_config.js
@@ -5,5 +5,6 @@ export default {
 		assert.equal( component.get( 'c' ), 5 );
 		assert.equal( component.get( 'cSquared' ), 25 );
 		assert.equal( target.innerHTML, '<p>3 + 2 = 5</p>\n<p>5 * 5 = 25</p>' );
+		component.teardown();
 	}
 };
diff --git a/test/validator/computed-values/errors.json b/test/validator/properties-computed-values-needs-arguments/errors.json
similarity index 100%
rename from test/validator/computed-values/errors.json
rename to test/validator/properties-computed-values-needs-arguments/errors.json
diff --git a/test/validator/computed-values/input.html b/test/validator/properties-computed-values-needs-arguments/input.html
similarity index 100%
rename from test/validator/computed-values/input.html
rename to test/validator/properties-computed-values-needs-arguments/input.html