From 245dcc304779b11c95856e06e88b82d69e16e0e3 Mon Sep 17 00:00:00 2001
From: Tobias Koppers <tobias.koppers@googlemail.com>
Date: Tue, 20 Jun 2017 16:13:32 +0200
Subject: [PATCH] better error message for missing internal names

---
 lib/optimize/ConcatenatedModule.js | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lib/optimize/ConcatenatedModule.js b/lib/optimize/ConcatenatedModule.js
index cecdf321e6f..05460dff2ec 100644
--- a/lib/optimize/ConcatenatedModule.js
+++ b/lib/optimize/ConcatenatedModule.js
@@ -24,7 +24,10 @@ function getFinalName(info, exportName, moduleToInfoMap, requestShortener) {
 	if(directExport) {
 		if(exportName === true)
 			info.needNamespaceObject = true;
-		return info.internalNames.get(directExport);
+		const name = info.internalNames.get(directExport);
+		if(!name)
+			throw new Error(`The export "${directExport}" in "${info.module.readableIdentifier(requestShortener)}" has no internal name`);
+		return name;
 	}
 	const reexport = info.reexportMap.get(exportName);
 	if(reexport) {
@@ -380,8 +383,6 @@ class ConcatenatedModule extends Module {
 						exportName = referencedModule.module.providedExports[exportIdx];
 					}
 					const finalName = getFinalName(referencedModule, exportName, moduleToInfoMap, requestShortener);
-					if(!finalName)
-						throw new Error(`Cannot map to variable name in module ${info.module.resource} (export '${exportName}')`);
 					const r = reference.identifier.range;
 					const source = info.source;
 					source.replace(r[0], r[1] - 1, finalName);