warn on unused helpers - fixes #1704

src/compile/Component.ts

@@ -260,8 +260,7 @@ export default class Component {
 		if (this.defaultExport) {
 			const categories = {
 				components: 'component',
-				// TODO helpers require a bit more work — need to analyse all expressions
-				// helpers: 'helper',
+				helpers: 'helper',
 				events: 'event definition',
 				transitions: 'transition',
 				actions: 'actions',

src/compile/nodes/shared/Expression.ts

@@ -115,6 +115,8 @@ export default class Expression {
 						let object = node;
 						while (object.type === 'MemberExpression') object = object.object;
 
+						component.used.helpers.add(name);
+
 						const alias = component.templateVars.get(`helpers-${name}`);
 						if (alias !== name) code.overwrite(object.start, object.end, alias);
 						return;

test/validator/samples/method-nonexistent-helper/warnings.json

@@ -1,15 +1,32 @@
-[{
-	"code": "invalid-callee",
-	"message": "'foo' is an invalid callee (should be one of this.*, refs.*, event.*, options.*, console.*, set, fire, destroy or bar). 'foo' exists on 'helpers', did you put it in the wrong place?",
-	"pos": 18,
-	"start": {
-		"line": 1,
-		"column": 18,
-		"character": 18
+[
+	{
+		"code": "invalid-callee",
+		"message": "'foo' is an invalid callee (should be one of this.*, refs.*, event.*, options.*, console.*, set, fire, destroy or bar). 'foo' exists on 'helpers', did you put it in the wrong place?",
+		"pos": 18,
+		"start": {
+			"line": 1,
+			"column": 18,
+			"character": 18
+		},
+		"end": {
+			"line": 1,
+			"column": 23,
+			"character": 23
+		}
 	},
-	"end": {
-		"line": 1,
-		"column": 23,
-		"character": 23
+	{
+		"code": "unused-helper",
+		"message": "The 'foo' helper is unused",
+		"start": {
+			"line": 12,
+			"column": 3,
+			"character": 126
+		},
+		"end": {
+			"line": 14,
+			"column": 4,
+			"character": 156
+		},
+		"pos": 126
 	}
-}]
+]

test/validator/samples/unused-helper.skip/warnings.json

@@ -1,8 +0,0 @@
-[{
-	"message": "The 'uppercase' helper is unused",
-	"start": {
-		"line": 4,
-		"column": 3
-	},
-	"pos": 43
-}]

test/validator/samples/unused-helper/warnings.json

@@ -0,0 +1,15 @@
+[{
+	"code": "unused-helper",
+	"message": "The 'uppercase' helper is unused",
+	"start": {
+		"line": 4,
+		"column": 3,
+		"character": 43
+	},
+	"end": {
+		"line": 4,
+		"column": 34,
+		"character": 74
+	},
+	"pos": 43
+}]