Fix compilation of SpEL elvis/ternary expressions

Without this fix the compiled version of elvis
actual behaved differently to the interpreted version
if the value being queried was an empty string. This
is now fixed. It also now correctly handles the
query value being a primitive and addresses the
findings of SPR-15192 where some type inferencing
logic was trying to be too clever, that code has
been deleted.

Issue: SPR-15192

spring-expression/src/main/java/org/springframework/expression/spel/ast/Elvis.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -49,6 +49,7 @@ public class Elvis extends SpelNodeImpl {
 	@Override
 	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
 		TypedValue value = this.children[0].getValueInternal(state);
+		// If this check is changed, the generateCode method will need changing too
 		if (!StringUtils.isEmpty(value.getValue())) {
 			return value;
 		}
@@ -77,11 +78,17 @@ public class Elvis extends SpelNodeImpl {
 		// exit type descriptor can be null if both components are literal expressions
 		computeExitTypeDescriptor();
 		this.children[0].generateCode(mv, cf);
+		CodeFlow.insertBoxIfNecessary(mv, cf.lastDescriptor().charAt(0));
 		Label elseTarget = new Label();
 		Label endOfIf = new Label();
 		mv.visitInsn(DUP);
 		mv.visitJumpInsn(IFNULL, elseTarget);
-		mv.visitJumpInsn(GOTO, endOfIf);
+		// Also check if empty string, as per the code in the interpreted version
+		mv.visitInsn(DUP);
+		mv.visitLdcInsn("");
+		mv.visitInsn(SWAP);
+		mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/String", "equals", "(Ljava/lang/Object;)Z",false);
+		mv.visitJumpInsn(IFEQ, endOfIf); // If not empty, drop through to elseTarget
 		mv.visitLabel(elseTarget);
 		mv.visitInsn(POP);
 		this.children[1].generateCode(mv, cf);
@@ -100,12 +107,6 @@ public class Elvis extends SpelNodeImpl {
 			if (conditionDescriptor.equals(ifNullValueDescriptor)) {
 				this.exitTypeDescriptor = conditionDescriptor;
 			}
-			else if (conditionDescriptor.equals("Ljava/lang/Object") && !CodeFlow.isPrimitive(ifNullValueDescriptor)) {
-				this.exitTypeDescriptor = ifNullValueDescriptor;
-			}
-			else if (ifNullValueDescriptor.equals("Ljava/lang/Object") && !CodeFlow.isPrimitive(conditionDescriptor)) {
-				this.exitTypeDescriptor = conditionDescriptor;
-			}
 			else {
 				// Use the easiest to compute common super type
 				this.exitTypeDescriptor = "Ljava/lang/Object";

spring-expression/src/main/java/org/springframework/expression/spel/ast/Ternary.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -71,12 +71,6 @@ public class Ternary extends SpelNodeImpl {
 			if (leftDescriptor.equals(rightDescriptor)) {
 				this.exitTypeDescriptor = leftDescriptor;
 			}
-			else if (leftDescriptor.equals("Ljava/lang/Object") && !CodeFlow.isPrimitive(rightDescriptor)) {
-				this.exitTypeDescriptor = rightDescriptor;
-			}
-			else if (rightDescriptor.equals("Ljava/lang/Object") && !CodeFlow.isPrimitive(leftDescriptor)) {
-				this.exitTypeDescriptor = leftDescriptor;
-			}
 			else {
 				// Use the easiest to compute common super type
 				this.exitTypeDescriptor = "Ljava/lang/Object";

spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java

@@ -17,8 +17,10 @@
 package org.springframework.expression.spel;
 
 import java.io.IOException;
+import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -4627,6 +4629,188 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		assertEquals(3, expression.getValue(root));
 	}
 	
+	@Test
+	public void elvisOperator_SPR15192() {
+		SpelParserConfiguration configuration = new SpelParserConfiguration(SpelCompilerMode.IMMEDIATE, null);
+		Expression exp;
+		
+		exp = new SpelExpressionParser(configuration).parseExpression("bar()");
+		assertEquals("BAR", exp.getValue(new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("BAR", exp.getValue(new Foo(), String.class));
+		assertIsCompiled(exp);
+ 
+		exp = new SpelExpressionParser(configuration).parseExpression("bar('baz')");
+		assertEquals("BAZ", exp.getValue(new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("BAZ", exp.getValue(new Foo(), String.class));
+		assertIsCompiled(exp);
+ 
+		StandardEvaluationContext context = new StandardEvaluationContext();
+		context.setVariable("map", Collections.singletonMap("foo", "qux"));
+ 
+		exp = new SpelExpressionParser(configuration).parseExpression("bar(#map['foo'])");
+		assertEquals("QUX", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("QUX", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+ 
+		exp = new SpelExpressionParser(configuration).parseExpression("bar(#map['foo'] ?: 'qux')");
+		assertEquals("QUX", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("QUX", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// When the condition is a primitive
+		exp = new SpelExpressionParser(configuration).parseExpression("3?:'foo'");
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// When the condition is a double slot primitive
+		exp = new SpelExpressionParser(configuration).parseExpression("3L?:'foo'");
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+
+		// When the condition is an empty string
+		exp = new SpelExpressionParser(configuration).parseExpression("''?:4L");
+		assertEquals("4", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("4", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// null condition
+		exp = new SpelExpressionParser(configuration).parseExpression("null?:4L");
+		assertEquals("4", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("4", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+
+		// variable access returning primitive
+		exp = new SpelExpressionParser(configuration).parseExpression("#x?:'foo'");
+		context.setVariable("x",50);
+		assertEquals("50", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("50", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+
+		exp = new SpelExpressionParser(configuration).parseExpression("#x?:'foo'");
+		context.setVariable("x",null);
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// variable access returning array
+		exp = new SpelExpressionParser(configuration).parseExpression("#x?:'foo'");
+		context.setVariable("x",new int[]{1,2,3});
+		assertEquals("1,2,3", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("1,2,3", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+	}
+
+	@Test
+	public void ternaryOperator_SPR15192() {
+		SpelParserConfiguration configuration = new SpelParserConfiguration(SpelCompilerMode.IMMEDIATE, null);
+		Expression exp;
+		StandardEvaluationContext context = new StandardEvaluationContext();
+		context.setVariable("map", Collections.singletonMap("foo", "qux"));
+ 
+		exp = new SpelExpressionParser(configuration).parseExpression("bar(#map['foo'] != null ? #map['foo'] : 'qux')");
+		assertEquals("QUX", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("QUX", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		exp = new SpelExpressionParser(configuration).parseExpression("3==3?3:'foo'");
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		exp = new SpelExpressionParser(configuration).parseExpression("3!=3?3:'foo'");
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// When the condition is a double slot primitive
+		exp = new SpelExpressionParser(configuration).parseExpression("3==3?3L:'foo'");
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("3", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		exp = new SpelExpressionParser(configuration).parseExpression("3!=3?3L:'foo'");
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+
+		// When the condition is an empty string
+		exp = new SpelExpressionParser(configuration).parseExpression("''==''?'abc':4L");
+		assertEquals("abc", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("abc", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// null condition
+		exp = new SpelExpressionParser(configuration).parseExpression("3==3?null:4L");
+		assertEquals(null, exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals(null, exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+
+		// variable access returning primitive
+		exp = new SpelExpressionParser(configuration).parseExpression("#x==#x?50:'foo'");
+		context.setVariable("x",50);
+		assertEquals("50", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("50", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+
+		exp = new SpelExpressionParser(configuration).parseExpression("#x!=#x?50:'foo'");
+		context.setVariable("x",null);
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("foo", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+		
+		// variable access returning array
+		exp = new SpelExpressionParser(configuration).parseExpression("#x==#x?'1,2,3':'foo'");
+		context.setVariable("x",new int[]{1,2,3});
+		assertEquals("1,2,3", exp.getValue(context, new Foo(), String.class));
+		assertCanCompile(exp);
+		assertEquals("1,2,3", exp.getValue(context, new Foo(), String.class));
+		assertIsCompiled(exp);
+	}
+
+	private void assertIsCompiled(Expression ex) {
+		try {
+			Field f = SpelExpression.class.getDeclaredField("compiledAst");
+			f.setAccessible(true);
+			Object object = f.get(ex);
+			assertNotNull(object);
+		} catch (Exception e) {
+			fail(e.toString());
+		}
+	}
+ 
+	public static class Foo {
+ 
+		public String bar() {
+			return "BAR";
+		}
+ 
+		public String bar(String arg) {
+			return arg.toUpperCase();
+		}
+ 
+	}
+ 
+
 
 	// helper methods