Blame Urllib problems on the callers

For Crashlytics.

The previous attempt at doing this failed, because it tried to modify
the *first* exception in the chain, but it turns out that it's the
*last* exception in the chain that Crashlytics looks at.

So given an Exception...
"
java.lang.Exception: This is a test Exception
    at not.bankdroid.at.all.ExceptionFactory.getException(ExceptionFactory.java:20)
    at com.liato.bankdroid.utils.ExceptionUtilsTest.testBlameBankdroid(ExceptionUtilsTest.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at ...
"
... we now report to Crashlytics:
"
java.lang.Exception: This is a test Exception
    at not.bankdroid.at.all.ExceptionFactory.getException(ExceptionFactory.java:20)
    at com.liato.bankdroid.utils.ExceptionUtilsTest.testBlameBankdroid(ExceptionUtilsTest.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at ...
Caused by: java.lang.Exception: This is a test Exception
    at com.liato.bankdroid.utils.ExceptionUtilsTest.testBlameBankdroid(ExceptionUtilsTest.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at ...
    ... 37 more
"

bankdroid-legacy/src/main/java/com/liato/bankdroid/utils/ExceptionUtils.java

@@ -1,6 +1,8 @@
 package com.liato.bankdroid.utils;
 
+import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
+import android.support.annotation.VisibleForTesting;
 
 import java.lang.reflect.InvocationTargetException;
 import java.util.Arrays;
@@ -11,41 +13,109 @@ public class ExceptionUtils {
     private static final String PREFIX = "com.liato.bankdroid.";
 
     /**
-     * Take an exception thrown and make it look like it came from Bankdroid.
+     * Modify an Exception to make it look like it was ultimately caused by Bankdroid.
      * <p/>
-     * Specifically, if Urllib.java, called by Bankdroid code, throws an exception,
-     * rewrite the exception so that it appears as if it was thrown from the
-     * Bankdroid method calling Urllib, but caused by the original Exception.
+     * The purpose is to make Crashlytics report Urllib exceptions as coming from whatever
+     * bank Urllib is trying to access.
+     * <p/>
+     * For example, this exception:
+     * <pre>
+     * java.lang.Exception: This is a test Exception
+     *     at not.bankdroid.at.all.ExceptionFactory.getException(ExceptionFactory.java:20)
+     *     at com.liato.bankdroid.utils.ExceptionUtilsTest.testBlameBankdroid(ExceptionUtilsTest.java:16)
+     *     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
+     *     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
+     *     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
+     *     at java.lang.reflect.Method.invoke(Method.java:497)
+     *     at ...
+     * </pre>
+     *
+     * Would be turned into this exception:
+     * <pre>
+     * java.lang.Exception: This is a test Exception
+     *     at not.bankdroid.at.all.ExceptionFactory.getException(ExceptionFactory.java:20)
+     *     at com.liato.bankdroid.utils.ExceptionUtilsTest.testBlameBankdroid(ExceptionUtilsTest.java:16)
+     *     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
+     *     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
+     *     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
+     *     at java.lang.reflect.Method.invoke(Method.java:497)
+     *     at ...
+     * Caused by: java.lang.Exception: This is a test Exception
+     *     at com.liato.bankdroid.utils.ExceptionUtilsTest.testBlameBankdroid(ExceptionUtilsTest.java:16)
+     *     at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
+     *     at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
+     *     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
+     *     at java.lang.reflect.Method.invoke(Method.java:497)
+     *     at ...
+     *     ... 37 more
+     * </pre>
      */
-    public static <T extends Throwable> T bankdroidifyException(T exception) {
+    public static void blameBankdroid(Throwable exception) {
+        Throwable ultimateCause = getUltimateCause(exception);
+        if (ultimateCause == null) {
+            // Unable to find ultimate cause, never mind
+            return;
+        }
+
         StackTraceElement[] bankdroidifiedStacktrace =
-                bankdroidifyStacktrace(exception.getStackTrace());
-        if (bankdroidifiedStacktrace.length == exception.getStackTrace().length) {
-            // Unable to bankdroidify stacktrace, never mind
-            return exception;
+                bankdroidifyStacktrace(ultimateCause.getStackTrace());
+        if (bankdroidifiedStacktrace.length == 0) {
+            // No Bankdroid stack frames found, never mind
+            return;
+        }
+        if (bankdroidifiedStacktrace.length == ultimateCause.getStackTrace().length) {
+            // Bankdroid already to blame, never mind
+            return;
         }
 
-        T returnMe = createWrapperException(exception);
-        if (returnMe == null) {
+        Throwable fakeCause = cloneException(ultimateCause);
+        if (fakeCause == null) {
             Timber.w(new RuntimeException(
-                    "Unable to bankdroidify exception of class: " + exception.getClass()));
-            return exception;
+                    "Unable to bankdroidify exception of class: " + ultimateCause.getClass()));
+            return;
         }
 
-        returnMe.initCause(exception);
+        // Put the bankdroidified stack trace before the fakeCause's actual stack trace
+        fakeCause.setStackTrace(concatArrays(bankdroidifiedStacktrace, fakeCause.getStackTrace()));
 
-        returnMe.setStackTrace(bankdroidifiedStacktrace);
+        ultimateCause.initCause(fakeCause);
+    }
 
+    @VisibleForTesting
+    static StackTraceElement[] concatArrays(StackTraceElement[] a, StackTraceElement[] b) {
+        StackTraceElement[] returnMe = new StackTraceElement[a.length + b.length];
+        System.arraycopy(a, 0, returnMe, 0, a.length);
+        System.arraycopy(b, 0, returnMe, a.length, b.length);
         return returnMe;
     }
 
+    @VisibleForTesting
+    @Nullable
+    static Throwable getUltimateCause(Throwable t) {
+        int laps = 0;
+        Throwable ultimateCause = t;
+        while (ultimateCause.getCause() != null) {
+            ultimateCause = ultimateCause.getCause();
+            if (laps++ > 10) {
+                return null;
+            }
+        }
+        return ultimateCause;
+    }
+
+    /**
+     * Clone message and stacktrace but not the cause.
+     */
     @Nullable
-    private static <T extends Throwable> T createWrapperException(T wrapMe) {
+    @VisibleForTesting
+    static <T extends Throwable> T cloneException(T wrapMe) {
         Class<?> newClass = wrapMe.getClass();
         while (newClass != null) {
             try {
-                return (T) newClass.getConstructor(String.class)
-                        .newInstance(wrapMe.getMessage());
+                T returnMe =
+                        (T) newClass.getConstructor(String.class).newInstance(wrapMe.getMessage());
+                returnMe.setStackTrace(wrapMe.getStackTrace());
+                return returnMe;
             } catch (InvocationTargetException e) {
                 newClass = newClass.getSuperclass();
             } catch (NoSuchMethodException e) {
@@ -63,9 +133,12 @@ private static <T extends Throwable> T createWrapperException(T wrapMe) {
     /**
      * Remove all initial non-Bankdroid frames from a stack.
      *
-     * @return A copy of rawStack but with the initial non-Bankdroid frames removed
+     * @return A copy of rawStack but with the initial non-Bankdroid frames removed, or null
+     * if no sensible answer can be given.
      */
-    private static StackTraceElement[] bankdroidifyStacktrace(final StackTraceElement[] rawStack) {
+    @VisibleForTesting
+    @NonNull
+    static StackTraceElement[] bankdroidifyStacktrace(final StackTraceElement[] rawStack) {
         for (int i = 0; i < rawStack.length; i++) {
             StackTraceElement stackTraceElement = rawStack[i];
             if (stackTraceElement.getClassName().startsWith(PREFIX)) {
@@ -74,6 +147,6 @@ private static StackTraceElement[] bankdroidifyStacktrace(final StackTraceElemen
         }
 
         // No Bankdroid stack frames found, never mind
-        return rawStack;
+        return new StackTraceElement[0];
     }
 }

bankdroid-legacy/src/main/java/eu/nullbyte/android/urllib/Urllib.java

@@ -149,7 +149,8 @@ public String open(String url) throws ClientProtocolException, IOException {
         try {
             return this.open(url, new ArrayList<NameValuePair>());
         } catch (IOException e) {
-            throw ExceptionUtils.bankdroidifyException(e);
+            ExceptionUtils.blameBankdroid(e);
+            throw e;
         }
     }
 
@@ -162,7 +163,8 @@ public String open(String url, List<NameValuePair> postData)
         try {
             return open(url, postData, false);
         } catch (IOException e) {
-            throw ExceptionUtils.bankdroidifyException(e);
+            ExceptionUtils.blameBankdroid(e);
+            throw e;
         }
     }
 
@@ -182,7 +184,8 @@ public HttpResponse openAsHttpResponse(String url, List<NameValuePair> postData,
         try {
             return openAsHttpResponse(url, entity, forcePost);
         } catch (IOException e) {
-            throw ExceptionUtils.bankdroidifyException(e);
+            ExceptionUtils.blameBankdroid(e);
+            throw e;
         }
     }
 
@@ -200,7 +203,8 @@ public HttpResponse openAsHttpResponse(String url, HttpEntity entity, boolean fo
                 return openAsHttpResponse(url, entity, HttpMethod.POST);
             }
         } catch (IOException e) {
-            throw ExceptionUtils.bankdroidifyException(e);
+            ExceptionUtils.blameBankdroid(e);
+            throw e;
         }
     }
 
@@ -293,7 +297,8 @@ public InputStream openStream(String url, String postData, boolean forcePost)
             return openStream(url, postData != null ? new StringEntity(postData, this.charset) : null,
                     forcePost);
         } catch (IOException e) {
-            throw ExceptionUtils.bankdroidifyException(e);
+            ExceptionUtils.blameBankdroid(e);
+            throw e;
         }
     }