Be defensive adding additional imported configs

Refine the logic introduced in commit 71c6eb2b so that additional
imported @Configuration classes are not considered as candidates if
they have already been parsed.

Issue: SPR-12233

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassPostProcessor.java

@@ -322,10 +322,15 @@ public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPo
 			if (registry.getBeanDefinitionCount() > candidateNames.length) {
 				String[] newCandidateNames = registry.getBeanDefinitionNames();
 				Set<String> oldCandidateNames = new HashSet<String>(Arrays.asList(candidateNames));
+				Set<String> alreadyParsedClasses = new HashSet<String>();
+				for (ConfigurationClass configurationClass : alreadyParsed) {
+					alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
+				}
 				for (String candidateName : newCandidateNames) {
 					if (!oldCandidateNames.contains(candidateName)) {
 						BeanDefinition beanDef = registry.getBeanDefinition(candidateName);
-						if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
+						if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)
+								&& !alreadyParsedClasses.contains(beanDef.getBeanClassName())) {
 							configCandidates.add(new BeanDefinitionHolder(beanDef, candidateName));
 						}
 					}

spring-context/src/test/java/org/springframework/context/annotation/spr12233/Spr12233Tests.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2002-2014 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.context.annotation.spr12233;
+
+import org.junit.Test;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.ConditionContext;
+import org.springframework.context.annotation.Conditional;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.ConfigurationCondition;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
+import org.springframework.core.type.AnnotatedTypeMetadata;
+
+
+/**
+ * Tests cornering the regression reported in SPR-12233.
+ *
+ * @author Phillip Webb
+ */
+public class Spr12233Tests {
+
+	@Test
+	public void spr12233() throws Exception {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
+		ctx.register(PropertySourcesPlaceholderConfigurer.class);
+		ctx.register(ImportConfiguration.class);
+		ctx.refresh();
+		ctx.close();
+	}
+
+	static class NeverConfigurationCondition implements ConfigurationCondition {
+		@Override
+		public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
+			return false;
+		}
+
+		@Override
+		public ConfigurationPhase getConfigurationPhase() {
+			return ConfigurationPhase.REGISTER_BEAN;
+		}
+	}
+
+	@Import(ComponentScanningConfiguration.class)
+	static class ImportConfiguration {
+
+	}
+
+	@Configuration
+	@ComponentScan
+	static class ComponentScanningConfiguration {
+
+	}
+
+
+	@Configuration
+	@Conditional(NeverConfigurationCondition.class)
+	static class ConditionWithPropertyValueInjection {
+
+		@Value("${idontexist}")
+		private String property;
+	}
+}