Merge pull request #103 from rustyx/master

Improved reflection error handling

Author: spullara

compiler/src/main/java/com/github/mustachejava/MustacheException.java

@@ -4,6 +4,8 @@
  * Generally there is nothing you can do if it fails.
  */
 public class MustacheException extends RuntimeException {
+  private TemplateContext context;
+  
   public MustacheException() {
     super();
   }
@@ -16,7 +18,23 @@ public MustacheException(String s, Throwable throwable) {
     super(s, throwable);
   }
 
+  public MustacheException(String s, Throwable throwable, TemplateContext context) {
+    super(s, throwable);
+    this.context = context;
+  }
+
   public MustacheException(Throwable throwable) {
     super(throwable);
   }
+  
+  @Override
+  public String getMessage() {
+    return context == null ? super.getMessage() : super.getMessage() + " @" + context;
+  }
+  
+  public void setContext(TemplateContext context) {
+    if (this.context == null)
+      this.context = context;
+  }
+  
 }

compiler/src/main/java/com/github/mustachejava/codes/DefaultCode.java

@@ -137,10 +137,11 @@ public Object get(Object[] scopes) {
     }
     try {
       return binding.get(scopes);
-    } catch (Exception e) {
-      throw new MustacheException(e.getMessage() + "@" + tc.toString(), e);
-    } catch (Error e) {
-      throw new MustacheException(e.getMessage() + "@" + tc.toString(), e);
+    } catch (MustacheException e) {
+      e.setContext(tc);
+      throw e;
+    } catch (Throwable e) {
+      throw new MustacheException(e.getMessage(), e, tc);
     }
   }
 

compiler/src/main/java/com/github/mustachejava/codes/ValueCode.java

@@ -57,21 +57,21 @@ public ValueCode(TemplateContext tc, DefaultMustacheFactory df, String variable,
 
   @Override
   public Writer execute(Writer writer, final Object[] scopes) {
-    final Object object = get(scopes);
-    if (object != null) {
-      try {
+    try {
+      final Object object = get(scopes);
+      if (object != null) {
         if (object instanceof Function) {
           handleFunction(writer, (Function) object, scopes);
         } else if (object instanceof Callable) {
           return handleCallable(writer, (Callable) object, scopes);
         } else {
           execute(writer, oh.stringify(object));
         }
-      } catch (Exception e) {
-        throw new MustacheException("Failed to get value for " + name + " at line " + tc.file() + ":" + tc.line(), e);
       }
+      return super.execute(writer, scopes);
+    } catch (Exception e) {
+      throw new MustacheException("Failed to get value for " + name, e, tc);
     }
-    return super.execute(writer, scopes);
   }
 
   protected Writer handleCallable(Writer writer, final Callable callable, final Object[] scopes) throws Exception {

compiler/src/main/java/com/github/mustachejava/reflect/ReflectionWrapper.java

@@ -9,6 +9,7 @@
 import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.util.Arrays;
 
 /**
  * Used for evaluating values at a callsite
@@ -63,11 +64,15 @@ public Object call(Object[] scopes) throws GuardException {
         return method.invoke(scope, arguments);
       }
     } catch (IllegalArgumentException e) {
-      throw new MustacheException("Wrong method for object: " + method + " on " + scope, e);
-    } catch (InvocationTargetException e) {
-      throw new MustacheException("Failed to execute method: " + method, e.getTargetException());
+      throw new MustacheException("Error accessing " + getTargetDescription() + " on " + elementToString(scope)
+          + ", scope: [" + elementsToString(scopes, scopeIndex) + "]" + ", guards: " + Arrays.toString(guards), e);
     } catch (IllegalAccessException e) {
-      throw new MustacheException("Failed to execute method: " + method, e);
+      throw new MustacheException("Error accessing " + getTargetDescription() + " on " + elementToString(scope)
+          + ", scope: [" + elementsToString(scopes, scopeIndex) + "]" + ", guards: " + Arrays.toString(guards), e);
+    } catch (InvocationTargetException e) {
+      throw new MustacheException("Error invoking " + getTargetDescription() + " on " + elementToString(scope), e.getTargetException());
+    } catch (Exception e) {
+      throw new MustacheException("Error invoking " + getTargetDescription() + " on " + elementToString(scope), e);
     }
   }
 
@@ -102,4 +107,28 @@ public String toString() {
   public Wrapper[] getWrappers() {
     return wrappers;
   }
+
+  private String getTargetDescription() {
+    return method == null
+        ? "field " + field.getDeclaringClass() + "." + field.getName()
+        : "method " + method.getDeclaringClass().getCanonicalName() + "." + method.getName() + "(" + elementsToString(arguments, method.getParameterTypes().length - 1) + ")";
+  }
+  
+  private String elementsToString(Object[] objects, int showUpTo) {
+    if (objects == null || objects.length == 0 || showUpTo < 0) {
+      return "";
+    }
+    StringBuilder sb = new StringBuilder();
+    for (int i = 0; i <= showUpTo && i < objects.length; i++) {
+      if (sb.length() > 0)
+        sb.append(",");
+      sb.append(elementToString(objects[i]));
+    }
+    return sb.toString();
+  }
+
+  private String elementToString(Object object) {
+    return object == null ? null : object.getClass().getCanonicalName() + '@' + object.hashCode();
+  }
+  
 }

compiler/src/test/java/com/github/mustachejava/FailOnMissingTest.java

@@ -43,7 +43,7 @@ protected synchronized Wrapper getWrapper(String name, Object[] scopes) {
       test.execute(new StringWriter(), new Object());
       fail("Should have failed");
     } catch (MustacheException me) {
-      assertEquals("test not found in [test:1]@[test:1]", me.getMessage());
+      assertEquals("test not found in [test:1] @[test:1]", me.getCause().getMessage());
     } catch (IOException e) {
       e.printStackTrace();
     }