Merge pull request webpack#7441 from webpack/perf/mutate-reasons

sokra · web-flow · commit 3415a983301b · 2018-05-31T09:29:44.000+02:00
more performant changing of reasons
diff --git a/lib/optimize/SideEffectsFlagPlugin.js b/lib/optimize/SideEffectsFlagPlugin.js
@@ -106,6 +106,7 @@ class SideEffectsFlagPlugin {
 					for (const pair of reexportMaps) {
 						const module = pair[0];
 						const map = pair[1];
+						let newReasons = undefined;
 						for (let i = 0; i < module.reasons.length; i++) {
 							const reason = module.reasons[i];
 							const dep = reason.dependency;
@@ -117,7 +118,6 @@ class SideEffectsFlagPlugin {
 								if (mapping) {
 									dep.redirectedModule = mapping.module;
 									dep.redirectedId = mapping.exportName;
-									module.reasons.splice(i--, 1);
 									mapping.module.addReason(
 										reason.module,
 										dep,
@@ -126,8 +126,18 @@ class SideEffectsFlagPlugin {
 											  " (skipped side-effect-free modules)"
 											: "(skipped side-effect-free modules)"
 									);
+									// removing the currect reason, by not adding it to the newReasons array
+									// lazily create the newReasons array
+									if (newReasons === undefined) {
+										newReasons = i === 0 ? [] : module.reasons.slice(0, i);
+									}
+									continue;
 								}
 							}
+							if (newReasons !== undefined) newReasons.push(reason);
+						}
+						if (newReasons !== undefined) {
+							module.reasons = newReasons;
 						}
 					}
 				}
