fix: add environment variable to disable LWC version mismatch loglines

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

packages/@lwc/integration-karma/test/rendering/version-mismatch/index.spec.js

@@ -48,9 +48,23 @@ 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:`));
+            expect(dispatcher).not.toHaveBeenCalled();
+        });
+
         it('template', () => {
             function tmpl() {
                 return [];

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 [