only warn if really watching

Author: sokra

lib/CachePlugin.js

@@ -18,12 +18,17 @@ CachePlugin.prototype.apply = function(compiler) {
 	} else {
 		var _this = this;
 		compiler.plugin("compilation", function(compilation) {
-			if(compilation.notCacheable) {
-				compilation.warnings.push(new Error("CachePlugin - Cache cannot be used because of: " + compilation.notCacheable))
-			} else {
+			if(!compilation.notCacheable) {
 				compilation.cache = _this.cache;
+			} else if(_this.watching) {
+				compilation.warnings.push(
+					new Error("CachePlugin - Cache cannot be used because of: " + compilation.notCacheable)
+				);
 			}
 		});
+		compiler.plugin("watch-run", function() {
+			_this.watching = true;
+		});
 		compiler.plugin("run", function(compiler, callback) {
 			if(!compiler._lastCompilationFileDependencies) return callback();
 			var fs = compiler.inputFileSystem;