1 files changed, 231 insertions, 0 deletions
diff --git a/src/main/java/org/junit/internal/Throwables.java b/src/main/java/org/junit/internal/Throwables.java
index 86dceef..3f0f7a3 100644
--- a/src/main/java/org/junit/internal/Throwables.java
+++ b/src/main/java/org/junit/internal/Throwables.java
@@ -1,5 +1,17 @@
 package org.junit.internal;
 
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringReader;
+import java.io.StringWriter;
+import java.lang.reflect.Method;
+import java.util.AbstractList;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
 /**
  * Miscellaneous functions dealing with {@code Throwable}.
  *
@@ -39,4 +51,223 @@ public final class Throwables {
     private static <T extends Throwable> void rethrow(Throwable e) throws T {
         throw (T) e;
     }
+
+    /**
+     * Returns the stacktrace of the given Throwable as a String.
+     *
+     * @since 4.13
+     */
+    public static String getStacktrace(Throwable exception) {
+        StringWriter stringWriter = new StringWriter();
+        PrintWriter writer = new PrintWriter(stringWriter);
+        exception.printStackTrace(writer);
+        return stringWriter.toString();
+    }
+
+    /**
+     * Gets a trimmed version of the stack trace of the given exception. Stack trace
+     * elements that are below the test method are filtered out.
+     *
+     * @return a trimmed stack trace, or the original trace if trimming wasn't possible
+     */
+    public static String getTrimmedStackTrace(Throwable exception) {
+        List<String> trimmedStackTraceLines = getTrimmedStackTraceLines(exception);
+        if (trimmedStackTraceLines.isEmpty()) {
+            return getFullStackTrace(exception);
+        }
+
+        StringBuilder result = new StringBuilder(exception.toString());
+        appendStackTraceLines(trimmedStackTraceLines, result);
+        appendStackTraceLines(getCauseStackTraceLines(exception), result);
+        return result.toString();
+    }
+
+    private static List<String> getTrimmedStackTraceLines(Throwable exception) {
+        List<StackTraceElement> stackTraceElements = Arrays.asList(exception.getStackTrace());
+        int linesToInclude = stackTraceElements.size();
+
+        State state = State.PROCESSING_OTHER_CODE;
+        for (StackTraceElement stackTraceElement : asReversedList(stackTraceElements)) {
+            state = state.processStackTraceElement(stackTraceElement);
+            if (state == State.DONE) {
+                List<String> trimmedLines = new ArrayList<String>(linesToInclude + 2);
+                trimmedLines.add("");
+                for (StackTraceElement each : stackTraceElements.subList(0, linesToInclude)) {
+                    trimmedLines.add("\tat " + each);
+                }
+                if (exception.getCause() != null) {
+                    trimmedLines.add("\t... " + (stackTraceElements.size() - trimmedLines.size()) + " trimmed");
+                }
+                return trimmedLines;
+            }
+            linesToInclude--;
+        }
+        return Collections.emptyList();
+    }
+
+    private static final Method getSuppressed = initGetSuppressed();
+
+    private static Method initGetSuppressed() {
+        try {
+            return Throwable.class.getMethod("getSuppressed");
+        } catch (Throwable e) {
+            return null;
+        }
+    }
+
+    private static boolean hasSuppressed(Throwable exception) {
+        if (getSuppressed == null) {
+            return false;
+        }
+        try {
+            Throwable[] suppressed = (Throwable[]) getSuppressed.invoke(exception);
+            return suppressed.length != 0;
+        } catch (Throwable e) {
+            return false;
+        }
+    }
+
+    private static List<String> getCauseStackTraceLines(Throwable exception) {
+        if (exception.getCause() != null || hasSuppressed(exception)) {
+            String fullTrace = getFullStackTrace(exception);
+            BufferedReader reader = new BufferedReader(
+                    new StringReader(fullTrace.substring(exception.toString().length())));
+            List<String> causedByLines = new ArrayList<String>();
+    
+            try {
+                String line;
+                while ((line = reader.readLine()) != null) {
+                    if (line.startsWith("Caused by: ") || line.trim().startsWith("Suppressed: ")) {
+                        causedByLines.add(line);
+                        while ((line = reader.readLine()) != null) {
+                            causedByLines.add(line);
+                        }
+                        return causedByLines;
+                    }
+                }
+            } catch (IOException e) {
+                // We should never get here, because we are reading from a StringReader
+            }
+        }
+
+        return Collections.emptyList();
+    }
+
+    private static String getFullStackTrace(Throwable exception) {
+        StringWriter stringWriter = new StringWriter();
+        PrintWriter writer = new PrintWriter(stringWriter);
+        exception.printStackTrace(writer);
+        return stringWriter.toString();
+    }
+
+    private static void appendStackTraceLines(
+            List<String> stackTraceLines, StringBuilder destBuilder) {
+        for (String stackTraceLine : stackTraceLines) {
+            destBuilder.append(String.format("%s%n", stackTraceLine));
+        }
+    }
+
+    private static <T> List<T> asReversedList(final List<T> list) {
+        return new AbstractList<T>() {
+
+            @Override
+            public T get(int index) {
+                return list.get(list.size() - index - 1);
+            }
+
+            @Override
+            public int size() {
+                return list.size();
+            }
+        };
+    }
+
+    private enum State {
+        PROCESSING_OTHER_CODE {
+            @Override public State processLine(String methodName) {
+                if (isTestFrameworkMethod(methodName)) {
+                    return PROCESSING_TEST_FRAMEWORK_CODE;
+                }
+                return this;
+            }
+        },
+        PROCESSING_TEST_FRAMEWORK_CODE {
+            @Override public State processLine(String methodName) {
+                if (isReflectionMethod(methodName)) {
+                    return PROCESSING_REFLECTION_CODE;
+                } else if (isTestFrameworkMethod(methodName)) {
+                    return this;
+                }
+                return PROCESSING_OTHER_CODE;
+            } 
+        },
+        PROCESSING_REFLECTION_CODE {
+            @Override public State processLine(String methodName) {
+                if (isReflectionMethod(methodName)) {
+                    return this;
+                } else if (isTestFrameworkMethod(methodName)) {
+                    // This is here to handle TestCase.runBare() calling TestCase.runTest().
+                    return PROCESSING_TEST_FRAMEWORK_CODE;
+                }
+                return DONE;
+            } 
+        },
+        DONE {
+            @Override public State processLine(String methodName) {
+                return this;
+            } 
+        };
+
+        /** Processes a stack trace element method name, possibly moving to a new state. */
+        protected abstract State processLine(String methodName);
+        
+        /** Processes a stack trace element, possibly moving to a new state. */
+        public final State processStackTraceElement(StackTraceElement element) {
+            return processLine(element.getClassName() + "." + element.getMethodName() + "()");
+        }
+    }
+
+    private static final String[] TEST_FRAMEWORK_METHOD_NAME_PREFIXES = {
+        "org.junit.runner.",
+        "org.junit.runners.",
+        "org.junit.experimental.runners.",
+        "org.junit.internal.",
+        "junit.extensions",
+        "junit.framework",
+        "junit.runner",
+        "junit.textui",
+    };
+
+    private static final String[] TEST_FRAMEWORK_TEST_METHOD_NAME_PREFIXES = {
+        "org.junit.internal.StackTracesTest",
+    };
+
+    private static boolean isTestFrameworkMethod(String methodName) {
+        return isMatchingMethod(methodName, TEST_FRAMEWORK_METHOD_NAME_PREFIXES) &&
+                !isMatchingMethod(methodName, TEST_FRAMEWORK_TEST_METHOD_NAME_PREFIXES);
+    }
+    
+    private static final String[] REFLECTION_METHOD_NAME_PREFIXES = {
+        "sun.reflect.",
+        "java.lang.reflect.",
+        "jdk.internal.reflect.",
+        "org.junit.rules.RunRules.<init>(",
+        "org.junit.rules.RunRules.applyAll(", // calls TestRules
+        "org.junit.runners.RuleContainer.apply(", // calls MethodRules & TestRules
+        "junit.framework.TestCase.runBare(", // runBare() directly calls setUp() and tearDown()
+   };
+    
+    private static boolean isReflectionMethod(String methodName) {
+        return isMatchingMethod(methodName, REFLECTION_METHOD_NAME_PREFIXES);
+    }
+
+    private static boolean isMatchingMethod(String methodName, String[] methodNamePrefixes) {
+        for (String methodNamePrefix : methodNamePrefixes) {
+            if (methodName.startsWith(methodNamePrefix)) {
+                return true;
+            }
+        }
+        
+        return false;
+    }
 }