fix(ssr): fix adjacent text node concatenation

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/comments-at-end/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span>{foo}{bar}{baz}{foo}{bar}{baz}{foo}{bar}{baz}<!--lala--><!--hahaha--><!--yolo--></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/comments-then-element/expected.html

@@ -0,0 +1,9 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      ‍
+      <div>
+      </div>
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/comments-then-element/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span>{foo}{bar}{baz}<!--a--><!--b--><!--c--><div></div></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/emptier/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span>{foo}{bar}{baz}{foo}{bar}{baz}{foo}{bar}{baz}</span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/emptier/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/empty/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/empty2/expected.html

@@ -0,0 +1,7 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      ‍
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/empty3/expected.html

@@ -0,0 +1,7 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      ‍
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/html-escaping-single/expected.html

@@ -0,0 +1,7 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      &amp;minus;
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/html-escaping-single/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span>{foo}</span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/html-escaping-single/modules/x/comments-text/comments-text.js

@@ -0,0 +1,5 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '−';
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/html-escaping/expected.html

@@ -0,0 +1,7 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      &amp;minus;
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/html-escaping/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '&';
+    bar = 'minus';
+    baz = ';';
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/just-comments/expected.html

@@ -0,0 +1,6 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/just-comments/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span><!--a--><!--b--><!--c--></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/just-comments/modules/x/comments-text/comments-text.js

@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty-dynamic/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span>{foo}{bar}{baz}</span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty-literals-outside/expected.html

@@ -0,0 +1,7 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      totoyolototoyolo
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty-literals-outside/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span>toto{foo}yolo{bar}toto{baz}yolo</span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty-literals-outside/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty1/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty2/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/nonempty3/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/text-comment-text-comment/expected.html

@@ -0,0 +1,7 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      ‍
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/text-comment-text-comment/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/text-comment-text-comment/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template>
+    <span><!--a-->{foo}<!--b-->{bar}<!--c-->{baz}<!--d-->{foo}<!--e--></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-off/text-comment-text-comment/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/comments-then-element/expected.html

@@ -0,0 +1,12 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      ‍
+      <!--a-->
+      <!--b-->
+      <!--c-->
+      <div>
+      </div>
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/comments-then-element/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/comments-then-element/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template lwc:preserve-comments>
+    <span>{foo}{bar}{baz}<!--a--><!--b--><!--c--><div></div></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/comments-then-element/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier-with-text-comment-text/expected.html

@@ -0,0 +1,15 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      <!--a-->
+      ‍
+      <!--b-->
+      ‍
+      <!--c-->
+      ‍
+      <!--d-->
+      ‍
+      <!--e-->
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier-with-text-comment-text/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier-with-text-comment-text/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template lwc:preserve-comments>
+    <span><!--a-->{foo}<!--b-->{bar}<!--c-->{baz}<!--d-->{foo}<!--e--></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier-with-text-comment-text/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier/expected.html

@@ -0,0 +1,10 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      ‍
+      <!--lala-->
+      <!--hahaha-->
+      <!--yolo-->
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template lwc:preserve-comments>
+    <span>{foo}{bar}{baz}{foo}{bar}{baz}{foo}{bar}{baz}<!--lala--><!--hahaha--><!--yolo--></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/emptier/modules/x/comments-text/comments-text.js

@@ -0,0 +1,7 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {
+    foo = '';
+    bar = undefined;
+    baz = null;
+}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/just-comments/expected.html

@@ -0,0 +1,9 @@
+<x-comments-text>
+  <template shadowrootmode="open">
+    <span>
+      <!--a-->
+      <!--b-->
+      <!--c-->
+    </span>
+  </template>
+</x-comments-text>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/just-comments/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/just-comments/modules/x/comments-text/comments-text.html

@@ -0,0 +1,3 @@
+<template lwc:preserve-comments>
+    <span><!--a--><!--b--><!--c--></span>
+</template>

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/just-comments/modules/x/comments-text/comments-text.js

@@ -0,0 +1,3 @@
+import { LightningElement } from 'lwc';
+
+export default class extends LightningElement {}

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/preserve-comments/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/preserve-comments2/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/engine-server/src/__tests__/fixtures/adjacent-text-nodes/preserve-comments-on/preserve-comments3/index.js

@@ -0,0 +1,3 @@
+export const tagName = 'x-comments-text';
+export { default } from 'x/comments-text';
+export * from 'x/comments-text';

packages/@lwc/ssr-compiler/src/__tests__/utils/expected-failures.ts

@@ -8,11 +8,6 @@
 // We should slowly drive down these test failures or at least document where we expect the failures
 // TODO [#4815]: enable all SSR v2 tests
 export const expectedFailures = new Set([
-    'adjacent-text-nodes/empty/index.js',
-    'adjacent-text-nodes/with-comments/empty1/index.js',
-    'adjacent-text-nodes/with-comments/empty2/index.js',
-    'adjacent-text-nodes/with-comments/empty3/index.js',
-    'adjacent-text-nodes/with-comments/preserve-comments2/index.js',
     'attribute-aria/dynamic/index.js',
     'attribute-class/with-scoped-styles-only-in-child/dynamic/index.js',
     'attribute-class/with-scoped-styles/dynamic/index.js',

packages/@lwc/ssr-compiler/src/compile-template/shared.ts

@@ -145,3 +145,25 @@ export function getChildAttrsOrProps(
 
     return b.objectExpression(objectAttrsOrProps);
 }
+
+/**
+ * True if we should flush at the end of a series of text content nodes and/or comment nodes
+ * that are adjacent to one another as siblings. (Comment nodes are ignored when preserve-comments
+ * is turned off.) This allows for adjacent text node concatenation.
+ * @param cxt - TransformerContext
+ */
+export const shouldFlushTextContent = (cxt: TransformerContext) => {
+    const { nextSibling } = cxt;
+    if (!nextSibling) {
+        // we are the last sibling
+        return true;
+    }
+    switch (nextSibling.type) {
+        case 'Text':
+            return false;
+        case 'Comment':
+            return cxt.templateOptions.preserveComments;
+        default:
+            return true;
+    }
+};

packages/@lwc/ssr-compiler/src/compile-template/transformers/comment.ts

@@ -7,12 +7,25 @@
 
 import { builders as b } from 'estree-toolkit';
 
+import { esTemplateWithYield } from '../../estemplate';
+import { shouldFlushTextContent } from '../shared';
+import type { Statement as EsStatement } from 'estree';
 import type { Comment as IrComment } from '@lwc/template-compiler';
 import type { Transformer } from '../types';
 
+const bFlushTextContent = esTemplateWithYield`
+    yield flushTextContent();
+`<EsStatement>;
+
 export const Comment: Transformer<IrComment> = function Comment(node, cxt) {
     if (cxt.templateOptions.preserveComments) {
         return [b.expressionStatement(b.yieldExpression(b.literal(`<!--${node.value}-->`)))];
+    } else if (shouldFlushTextContent(cxt)) {
+        // If preserve comments is off, we check if we should flush text content
+        // for adjacent text nodes. (If preserve comments is on, then the previous
+        // text node already flushed.)
+        cxt.import('flushTextContent');
+        return [bFlushTextContent()];
     } else {
         return [];
     }