From 739776781bc28929127487e0a2a3bc36afe930fc Mon Sep 17 00:00:00 2001
From: Nicolas Kruk <nkruk@salesforce.com>
Date: Mon, 3 Feb 2025 18:01:09 -0500
Subject: [PATCH 1/4] fix: local dev logs LWC mismatch warnings on every SSR
 request

---
 .../src/framework/check-version-mismatch.ts    |  5 +++++
 .../rendering/version-mismatch/index.spec.js   | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts b/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts
index a8821a5f62..9b555336a2 100644
--- a/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts
+++ b/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts
@@ -38,6 +38,11 @@ export function checkVersionMismatch(
 ) {
     const versionMatcher = func.toString().match(LWC_VERSION_COMMENT_REGEX);
     if (!isNull(versionMatcher) && !warned) {
+        if (process.env.SKIP_LWC_VERSION_MISMATCH_CHECK === 'true') {
+            warned = true; // skip printing out version mismatch errors when env var is set
+            return;
+        }
+
         const version = versionMatcher[1];
         if (version !== LWC_VERSION) {
             warned = true; // only warn once to avoid flooding the console
diff --git a/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js b/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js
index a24f0c4701..65ad476fb5 100644
--- a/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js
+++ b/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js
@@ -48,9 +48,27 @@ describe('compiler version mismatch', () => {
         });
 
         afterEach(() => {
+            process.env.SKIP_LWC_VERSION_MISMATCH_CHECK = 'false';
             detachReportingControlDispatcher();
         });
 
+        it('skip warning during local dev', () => {
+            process.env.SKIP_LWC_VERSION_MISMATCH_CHECK = 'true';
+            function tmpl() {
+                return [];
+                /*LWC compiler v123.456.789*/
+            }
+
+            expect(() => {
+                registerTemplate(tmpl);
+            }).not.toLogErrorDev(
+                new RegExp(
+                    `LWC WARNING: current engine is v${process.env.LWC_VERSION}, but template was compiled with v123.456.789`
+                )
+            );
+            expect(dispatcher).not.toHaveBeenCalled();
+        });
+
         it('template', () => {
             function tmpl() {
                 return [];

From d135dbf60e0d4a3e579ce0cf3cac00979d020011 Mon Sep 17 00:00:00 2001
From: Nicolas Kruk <nkruk@salesforce.com>
Date: Mon, 3 Feb 2025 18:39:22 -0500
Subject: [PATCH 2/4] fix: null checks for safety

---
 .../@lwc/engine-core/src/framework/check-version-mismatch.ts    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts b/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts
index 9b555336a2..badcdb4f61 100644
--- a/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts
+++ b/packages/@lwc/engine-core/src/framework/check-version-mismatch.ts
@@ -38,7 +38,7 @@ export function checkVersionMismatch(
 ) {
     const versionMatcher = func.toString().match(LWC_VERSION_COMMENT_REGEX);
     if (!isNull(versionMatcher) && !warned) {
-        if (process.env.SKIP_LWC_VERSION_MISMATCH_CHECK === 'true') {
+        if (process?.env?.SKIP_LWC_VERSION_MISMATCH_CHECK === 'true') {
             warned = true; // skip printing out version mismatch errors when env var is set
             return;
         }

From c451d88578e75c406d934e82816df0f723cff6fa Mon Sep 17 00:00:00 2001
From: Nicolas Kruk <nkruk@salesforce.com>
Date: Wed, 26 Feb 2025 12:25:23 -0500
Subject: [PATCH 3/4] fix: tests

---
 .../test/rendering/version-mismatch/index.spec.js           | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js b/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js
index 65ad476fb5..dd44e7644e 100644
--- a/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js
+++ b/packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js
@@ -61,11 +61,7 @@ describe('compiler version mismatch', () => {
 
             expect(() => {
                 registerTemplate(tmpl);
-            }).not.toLogErrorDev(
-                new RegExp(
-                    `LWC WARNING: current engine is v${process.env.LWC_VERSION}, but template was compiled with v123.456.789`
-                )
-            );
+            }).not.toLogErrorDev(new RegExp(`LWC WARNING:`));
             expect(dispatcher).not.toHaveBeenCalled();
         });
 

From 55cb8f5369c7fae10bcd4682b8824a869c37a7bc Mon Sep 17 00:00:00 2001
From: Nicolas Kruk <nkruk@salesforce.com>
Date: Wed, 26 Feb 2025 12:26:36 -0500
Subject: [PATCH 4/4] fix: rollup comments

---
 scripts/rollup/rollup.config.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/scripts/rollup/rollup.config.js b/scripts/rollup/rollup.config.js
index ca267b48de..9314e0e1c7 100644
--- a/scripts/rollup/rollup.config.js
+++ b/scripts/rollup/rollup.config.js
@@ -55,6 +55,9 @@ function sharedPlugins() {
         // This is only used inside @lwc/engine-dom and @lwc/engine-server
         // Elsewhere, it _not_ be replaced, so that it can be replaced later (e.g. in @lwc/engine-core)
         'process.env.IS_BROWSER': packageName === '@lwc/engine-dom' ? 'true' : 'false',
+        ...(packageName === '@lwc/engine-dom'
+            ? { 'process.env.SKIP_LWC_VERSION_MISMATCH_CHECK': 'false' }
+            : {}),
     };
 
     return [