feat better error message for else,elseif,then,catch with unclosed tag

src/compiler/parse/index.ts

@@ -82,6 +82,15 @@ export class Parser {
 		return this.stack[this.stack.length - 1];
 	}
 
+	find_in_stack(fn) {
+		for (let i=this.stack.length -1; i>=0; i--) {
+			if (fn(this.stack[i])) {
+				return true;
+			}
+		}
+		return false;
+	}
+
 	acorn_error(err: any) {
 		this.error({
 			code: `parse-error`,

src/compiler/parse/state/mustache.ts

@@ -3,6 +3,7 @@ import read_expression from '../read/expression';
 import { closing_tag_omitted } from '../utils/html';
 import { whitespace } from '../../utils/patterns';
 import { trim_start, trim_end } from '../../utils/trim';
+import { to_string } from '../utils/node';
 import { Parser } from '../index';
 import { TemplateNode } from '../../interfaces';
 
@@ -106,11 +107,19 @@ export default function mustache(parser: Parser) {
 		// :else if
 		if (parser.eat('if')) {
 			const block = parser.current();
-			if (block.type !== 'IfBlock')
+			if (block.type !== 'IfBlock') {
+				if (parser.find_in_stack(block => block.type === 'IfBlock')) {
+					parser.error({
+						code: 'unclosed-open-tag',
+						message: `Expect to close ${to_string(block)} before {:else if ...} block`
+					});
+				}
+
 				parser.error({
 					code: `invalid-elseif-placement`,
 					message: 'Cannot have an {:else if ...} block outside an {#if ...} block'
 				});
+			}
 
 			parser.require_whitespace();
 
@@ -142,6 +151,13 @@ export default function mustache(parser: Parser) {
 		else {
 			const block = parser.current();
 			if (block.type !== 'IfBlock' && block.type !== 'EachBlock') {
+				if (parser.find_in_stack(block => block.type === 'IfBlock' || block.type === 'EachBlock')) {
+					parser.error({
+						code: 'unclosed-open-tag',
+						message: `Expect to close ${to_string(block)} before {:else} block`
+					});
+				}
+
 				parser.error({
 					code: `invalid-else-placement`,
 					message: 'Cannot have an {:else} block outside an {#if ...} or {#each ...} block'
@@ -166,13 +182,25 @@ export default function mustache(parser: Parser) {
 
 		if (is_then) {
 			if (block.type !== 'PendingBlock') {
+				if (parser.find_in_stack(block => block.type === 'PendingBlock')) {
+					parser.error({
+						code: 'unclosed-open-tag',
+						message: `Expect to close ${to_string(block)} before {:then} block`
+					});
+				}
 				parser.error({
 					code: `invalid-then-placement`,
 					message: 'Cannot have an {:then} block outside an {#await ...} block'
 				});
 			}
 		} else {
 			if (block.type !== 'ThenBlock' && block.type !== 'PendingBlock') {
+				if (parser.find_in_stack(block => block.type === 'ThenBlock' || block.type === 'PendingBlock')) {
+					parser.error({
+						code: 'unclosed-open-tag',
+						message: `Expect to close ${to_string(block)} before {:catch} block`
+					});
+				}
 				parser.error({
 					code: `invalid-catch-placement`,
 					message: 'Cannot have an {:catch} block outside an {#await ...} block'

src/compiler/parse/utils/node.ts

@@ -0,0 +1,30 @@
+import { TemplateNode } from '../../interfaces';
+
+export function to_string(node: TemplateNode) {
+	switch (node.type) {
+		case 'IfBlock':
+			return '{#if} block';
+		case 'ThenBlock':
+			return '{:then} block';
+		case 'ElseBlock':
+			return '{:else} block';
+		case 'PendingBlock':
+		case 'AwaitBlock':
+			return '{#await} block';
+		case 'CatchBlock':
+			return '{:catch} block';
+		case 'EachBlock':
+			return '{#each} block';
+		case 'RawMustacheTag':
+			return '{@html} block';
+		case 'DebugTag':
+			return '{@debug} block';
+		case 'Element':
+		case 'InlineComponent':
+		case 'Slot':
+		case 'Title':
+			return `<${node.name}> tag`;
+		default:
+			return node.type;
+	}
+}

test/parser/samples/error-catch-before-closing/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close {#each} block before {:catch} block",
+	"start": { "line": 3, "column": 9, "character": 44 },
+	"pos": 44
+}

test/parser/samples/error-catch-before-closing/input.svelte

@@ -0,0 +1,4 @@
+{#await true}
+  {#each foo as bar}
+  {:catch f}
+{/await}

test/parser/samples/error-else-before-closing-2/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close {#await} block before {:else} block",
+	"start": { "line": 3, "column": 8, "character": 32 },
+	"pos": 32
+}

test/parser/samples/error-else-before-closing-2/input.svelte

@@ -0,0 +1,4 @@
+{#if true}
+  {#await p}
+  {:else}
+{/if}

test/parser/samples/error-else-before-closing-3/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "invalid-else-placement",
+	"message": "Cannot have an {:else} block outside an {#if ...} or {#each ...} block",
+	"start": { "line": 2, "column": 6, "character": 11 },
+	"pos": 11
+}

test/parser/samples/error-else-before-closing-3/input.svelte

@@ -0,0 +1,2 @@
+<li>
+{:else}

test/parser/samples/error-else-before-closing/error-else-before-closing-2/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close {#await} block before {:else} block",
+	"start": { "line": 3, "column": 8, "character": 32 },
+	"pos": 32
+}

test/parser/samples/error-else-before-closing/error-else-before-closing-2/input.svelte

@@ -0,0 +1,4 @@
+{#if true}
+  {#await p}
+  {:else}
+{/if}

test/parser/samples/error-else-before-closing/error-else-before-closing-3/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "invalid-else-placement",
+	"message": "Cannot have an {:else} block outside an {#if ...} or {#each ...} block",
+	"start": { "line": 2, "column": 6, "character": 11 },
+	"pos": 11
+}

test/parser/samples/error-else-before-closing/error-else-before-closing-3/input.svelte

@@ -0,0 +1,2 @@
+<li>
+{:else}

test/parser/samples/error-else-before-closing/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close <li> tag before {:else} block",
+	"start": { "line": 3, "column": 8, "character": 26 },
+	"pos": 26
+}

test/parser/samples/error-else-before-closing/input.svelte

@@ -0,0 +1,4 @@
+{#if true}
+  <li>
+  {:else}
+{/if}

test/parser/samples/error-else-if-before-closing-2/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close <p> tag before {:else if ...} block",
+	"start": { "line": 3, "column": 11, "character": 28 },
+	"pos": 28
+}

test/parser/samples/error-else-if-before-closing-2/input.svelte

@@ -0,0 +1,4 @@
+{#if true}
+  <p>
+  {:else if false}
+{/if}

test/parser/samples/error-else-if-before-closing/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close {#await} block before {:else if ...} block",
+	"start": { "line": 3, "column": 11, "character": 37 },
+	"pos": 37
+}

test/parser/samples/error-else-if-before-closing/input.svelte

@@ -0,0 +1,4 @@
+{#if true}
+  {#await foo}
+  {:else if false}
+{/if}

test/parser/samples/error-else-if-without-if/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "invalid-elseif-placement",
+	"message": "Cannot have an {:else if ...} block outside an {#if ...} block",
+	"start": { "line": 3, "column": 11, "character": 36 },
+	"pos": 36
+}

test/parser/samples/error-else-if-without-if/input.svelte

@@ -0,0 +1,4 @@
+{#await foo}
+{:then bar}
+  {:else if}
+{/await}

test/parser/samples/error-then-before-closing/error.json

@@ -0,0 +1,6 @@
+{
+	"code": "unclosed-open-tag",
+	"message": "Expect to close <li> tag before {:then} block",
+	"start": { "line": 3, "column": 8, "character": 29 },
+	"pos": 29
+}

test/parser/samples/error-then-before-closing/input.svelte

@@ -0,0 +1,4 @@
+{#await true}
+  <li>
+  {:then f}
+{/await}