empty blocks are a dev warning, not an error

src/parse/state/mustache.ts

@@ -5,13 +5,6 @@ import reservedNames from '../../utils/reservedNames';
 import { Parser } from '../index';
 import { Node } from '../../interfaces';
 
-function isEmpty(nodes: Node[]) {
-	if (!nodes || nodes.length > 1) return false;
-	if (nodes.length === 0) return true;
-	if (nodes.length > 1) return false;
-	return nodes[0].type === 'Text' && !/\S/.test(nodes[0].data);
-}
-
 function trimWhitespace(block: Node, trimBefore: boolean, trimAfter: boolean) {
 	if (!block.children) return; // AwaitBlock
 
@@ -81,8 +74,6 @@ export default function mustache(parser: Parser) {
 		}
 
 		// strip leading/trailing whitespace as necessary
-		if (isEmpty(block.children)) parser.error(`Empty block`, block.start);
-
 		const charBefore = parser.template[block.start - 1];
 		const charAfter = parser.template[parser.index];
 		const trimBefore = !charBefore || whitespace.test(charBefore);

src/validate/html/index.ts

@@ -12,6 +12,13 @@ const meta = new Map([
 	[':Head', validateHead]
 ]);
 
+function isEmptyBlock(node: Node) {
+	if (!/Block$/.test(node.type) || !node.children) return false;
+	if (node.children.length > 1) return false;
+	const child = node.children[0];
+	return !child || (child.type === 'Text' && !/\S/.test(child.data));
+}
+
 export default function validateHtml(validator: Validator, html: Node) {
 	const refs = new Map();
 	const refCallees: Node[] = [];
@@ -58,6 +65,10 @@ export default function validateHtml(validator: Validator, html: Node) {
 			}
 		}
 
+		if (validator.options.dev && isEmptyBlock(node)) {
+			validator.warn('Empty block', node.start);
+		}
+
 		if (node.children) {
 			if (node.type === 'Element') elementStack.push(node);
 			stack.push(node);

src/validate/index.ts

@@ -93,7 +93,7 @@ export default function validate(
 	stylesheet: Stylesheet,
 	options: CompileOptions
 ) {
-	const { onwarn, onerror, name, filename, store } = options;
+	const { onwarn, onerror, name, filename, store, dev } = options;
 
 	try {
 		if (name && !/^[a-zA-Z_$][a-zA-Z_$0-9]*$/.test(name)) {
@@ -114,7 +114,8 @@ export default function validate(
 			onwarn,
 			name,
 			filename,
-			store
+			store,
+			dev
 		});
 
 		if (parsed.js) {

test/parser/samples/error-each-blocks-empty/input.html

@@ -1 +0,0 @@
-{{#each foos as foo}}{{/each}}

test/parser/samples/error-each-blocks-keyed-whitespace/error.json

@@ -1,8 +0,0 @@
-{
-	"message": "Empty block",
-	"loc": {
-		"line": 1,
-		"column": 0
-	},
-	"pos": 0
-}

test/parser/samples/error-each-blocks-keyed-whitespace/input.html

@@ -1,11 +0,0 @@
-{{#each foos as foo @id}}
-{{/each}}
-<script>
-	export default {
-		data: () => ({
-			foos: [
-				{ id: 5 }
-			]
-		})
-	};
-</script>

test/parser/samples/error-each-blocks-whitespace/error.json

@@ -1,8 +0,0 @@
-{
-	"message": "Empty block",
-	"loc": {
-		"line": 1,
-		"column": 0
-	},
-	"pos": 0
-}

test/parser/samples/error-each-blocks-whitespace/input.html

@@ -1,11 +0,0 @@
-{{#each foos as foo}}
-{{/each}}
-<script>
-  export default {
-    data: () => ({
-      foos: [
-        "id": 5
-      ]
-    })
-  };
-</script>

test/validator/index.js

@@ -1,6 +1,6 @@
 import * as fs from "fs";
 import assert from "assert";
-import { svelte, tryToLoadJson } from "../helpers.js";
+import { svelte, loadConfig, tryToLoadJson } from "../helpers.js";
 
 describe("validate", () => {
 	fs.readdirSync("test/validator/samples").forEach(dir => {
@@ -15,6 +15,7 @@ describe("validate", () => {
 		}
 
 		(solo ? it.only : skip ? it.skip : it)(dir, () => {
+			const config = loadConfig(`./validator/samples/${dir}/_config.js`);
 			const filename = `test/validator/samples/${dir}/input.html`;
 			const input = fs.readFileSync(filename, "utf-8").replace(/\s+$/, "");
 
@@ -32,7 +33,8 @@ describe("validate", () => {
 							pos: warning.pos,
 							loc: warning.loc
 						});
-					}
+					},
+					dev: config.dev
 				});
 
 				assert.deepEqual(warnings, expectedWarnings);

test/validator/samples/empty-block-dev.solo/_config.js

@@ -0,0 +1,3 @@
+export default {
+	dev: true
+};

test/validator/samples/empty-block-dev.solo/input.html

@@ -0,0 +1,3 @@
+{{#each things as thing}}
+
+{{/each}}

test/validator/samples/empty-block-dev.solo/warnings.json

@@ -1,8 +1,8 @@
-{
+[{
 	"message": "Empty block",
 	"loc": {
 		"line": 1,
 		"column": 0
 	},
 	"pos": 0
-}
+}]

test/validator/samples/empty-block-prod/input.html

@@ -0,0 +1,3 @@
+{{#each things as thing}}
+
+{{/each}}

test/validator/samples/empty-block-prod/warnings.json

@@ -0,0 +1 @@
+[]