allow inline stacktrace generation

README.md

@@ -1752,6 +1752,7 @@ is included in the logstash-logback-encoder library to format stacktraces by:
 * Using evaluators to determine if the stacktrace should be logged.
 * Outputting in either 'normal' order (root-cause-last), or root-cause-first.
 * Computing and inlining hexadecimal hashes for each exception stack using the `inlineHash` or `stackHash` provider ([more info](stack-hash.md)).
+* Use custom line separator for stack traces
 
 For example:
 
@@ -1766,6 +1767,7 @@ For example:
         <evaluator class="myorg.MyCustomEvaluator"/>
         <rootCauseFirst>true</rootCauseFirst>
         <inlineHash>true</inlineHash>
+        <lineSeparator>\\n</lineSeparator>
     </throwableConverter>
 </encoder>
 ```

src/main/java/net/logstash/logback/stacktrace/ShortenedThrowableConverter.java

@@ -40,6 +40,7 @@
 import ch.qos.logback.core.boolex.EvaluationException;
 import ch.qos.logback.core.boolex.EventEvaluator;
 import ch.qos.logback.core.status.ErrorStatus;
+import net.logstash.logback.encoder.SeparatorParser;
 
 /**
  * A {@link ThrowableHandlingConverter} (similar to logback's {@link ThrowableProxyConverter})
@@ -112,10 +113,15 @@ public class ShortenedThrowableConverter extends ThrowableHandlingConverter {
     private static final String OPTION_VALUE_ROOT_FIRST = "rootFirst";
     private static final String OPTION_VALUE_INLINE_HASH = "inlineHash";
 
+    private static final String OPTION_VALUE_INLINE_STACK = "inline";
+
     private static final int OPTION_INDEX_MAX_DEPTH = 0;
     private static final int OPTION_INDEX_SHORTENED_CLASS_NAME = 1;
     private static final int OPTION_INDEX_MAX_LENGTH = 2;
 
+    /** String sequence to use to delimit lines instead of {@link CoreConstants#LINE_SEPARATOR} when inline is active */
+    public static final String DEFAULT_INLINE_SEPARATOR = "\\n";
+
     private AtomicInteger errorCount = new AtomicInteger();
 
     /**
@@ -160,6 +166,9 @@ public class ShortenedThrowableConverter extends ThrowableHandlingConverter {
      */
     private boolean inlineHash;
 
+    /** line delimiter */
+    private String lineSeparator = CoreConstants.LINE_SEPARATOR;
+
     private StackElementFilter stackElementFilter;
 
     private StackHasher stackHasher;
@@ -217,13 +226,16 @@ private void parseOptions() {
                      * Remaining options are either
                      *     - "rootFirst" - indicating that stacks should be printed root-cause first
                      *     - "inlineHash" - indicating that hexadecimal error hashes should be computed and inlined
+                     *     - "inline" - indicating that the whole stack trace should be inlined, using "\\n" as separator
                      *     - evaluator name - name of evaluators that will determine if the stacktrace is ignored
                      *     - exclusion pattern - pattern for stack trace elements to exclude
                      */
                     if (OPTION_VALUE_ROOT_FIRST.equals(option)) {
                         setRootCauseFirst(true);
                     } else if (OPTION_VALUE_INLINE_HASH.equals(option)) {
                         setInlineHash(true);
+                    } else if (OPTION_VALUE_INLINE_STACK.equals(option)) {
+                        setLineSeparator(DEFAULT_INLINE_SEPARATOR);
                     } else {
                         @SuppressWarnings("rawtypes")
                         Map evaluatorMap = (Map) getContext().getObject(CoreConstants.EVALUATOR_MAP);
@@ -282,12 +294,36 @@ public String convert(ILoggingEvent event) {
             appendRootCauseLast(builder, null, ThrowableProxyUtil.REGULAR_EXCEPTION_INDENT, throwableProxy, stackHashes);
         }
         if (builder.length() > maxLength) {
-            builder.setLength(maxLength - ELLIPSIS.length() - CoreConstants.LINE_SEPARATOR.length());
-            builder.append(ELLIPSIS).append(CoreConstants.LINE_SEPARATOR);
+            builder.setLength(maxLength - ELLIPSIS.length() - getLineSeparator().length());
+            builder.append(ELLIPSIS).append(getLineSeparator());
         }
         return builder.toString();
     }
 
+    public String getLineSeparator() {
+        return lineSeparator;
+    }
+
+    /**
+     * Sets which lineSeparator to use between events.
+     * <p>
+     *
+     * The following values have special meaning:
+     * <ul>
+     * <li>{@code null} or empty string = no new line.</li>
+     * <li>"{@code SYSTEM}" = operating system new line (default).</li>
+     * <li>"{@code UNIX}" = unix line ending ({@code \n}).</li>
+     * <li>"{@code WINDOWS}" = windows line ending {@code \r\n}).</li>
+     * </ul>
+     * <p>
+     * Any other value will be used as given as the lineSeparator.
+     *
+     * @param lineSeparator the line separator
+     */
+    public void setLineSeparator(String lineSeparator) {
+        this.lineSeparator = SeparatorParser.parseSeparator(lineSeparator);
+    }
+
     /**
      * Return true if any evaluator returns true, indicating that
      * the stack trace should not be logged.
@@ -467,7 +503,7 @@ private void appendPlaceHolder(StringBuilder builder, int indent, int consecutiv
             .append(consecutiveExcluded)
             .append(" ")
             .append(message)
-            .append(CoreConstants.LINE_SEPARATOR);
+            .append(getLineSeparator());
     }
 
     /**
@@ -506,7 +542,7 @@ private void appendStackTraceElement(StringBuilder builder, int indent, StackTra
         if (shouldAppendPackagingData(step, previousStep)) {
             appendPackagingData(builder, step);
         }
-        builder.append(CoreConstants.LINE_SEPARATOR);
+        builder.append(getLineSeparator());
     }
 
     /**
@@ -547,7 +583,7 @@ private void appendFirstLine(StringBuilder builder, String prefix, int indent, I
         builder.append(abbreviator.abbreviate(throwableProxy.getClassName()))
             .append(": ")
             .append(throwableProxy.getMessage())
-            .append(CoreConstants.LINE_SEPARATOR);
+            .append(getLineSeparator());
     }
 
     private void indent(StringBuilder builder, int indent) {

src/test/java/net/logstash/logback/stacktrace/ShortenedThrowableConverterTest.java

@@ -315,17 +315,19 @@ public void testOptions() throws EvaluationException {
         assertThat(converter.getShortenedClassNameLength()).isEqualTo(ShortenedThrowableConverter.FULL_CLASS_NAME_LENGTH);
         assertThat(converter.getMaxLength()).isEqualTo(ShortenedThrowableConverter.FULL_MAX_LENGTH);
         assertThat(converter.isRootCauseFirst()).isTrue();
+        assertThat(converter.getLineSeparator()).isEqualTo(CoreConstants.LINE_SEPARATOR);
         assertThat(converter.getEvaluators().get(0)).isEqualTo(evaluator);
         assertThat(converter.getExcludes().get(0)).isEqualTo("regex");
 
         // test short values
-        converter.setOptionList(Arrays.asList("short", "short", "short", "rootFirst", "inlineHash", "evaluator", "regex"));
+        converter.setOptionList(Arrays.asList("short", "short", "short", "rootFirst", "inlineHash", "inline", "evaluator", "regex"));
         converter.start();
 
         assertThat(converter.getMaxDepthPerThrowable()).isEqualTo(ShortenedThrowableConverter.SHORT_MAX_DEPTH_PER_THROWABLE);
         assertThat(converter.getShortenedClassNameLength()).isEqualTo(ShortenedThrowableConverter.SHORT_CLASS_NAME_LENGTH);
         assertThat(converter.getMaxLength()).isEqualTo(ShortenedThrowableConverter.SHORT_MAX_LENGTH);
-
+        assertThat(converter.getLineSeparator()).isEqualTo(ShortenedThrowableConverter.DEFAULT_INLINE_SEPARATOR);
+
         // test numeric values
         converter.setOptionList(Arrays.asList("1", "2", "3"));
         converter.start();
@@ -424,6 +426,30 @@ public void test_inline_hash_root_cause_first() {
         }
     }
 
+    @Test
+    public void test_inline_stack() {
+        try {
+            StackTraceElementGenerator.generateCausedBy();
+            fail("Exception must have been thrown");
+        } catch (RuntimeException e) {
+            // GIVEN
+            StackHasher mockedHasher = Mockito.mock(StackHasher.class);
+            ShortenedThrowableConverter converter = new ShortenedThrowableConverter();
+            converter.setLineSeparator(ShortenedThrowableConverter.DEFAULT_INLINE_SEPARATOR);
+            converter.setRootCauseFirst(true);
+            converter.start();
+            converter.setStackHasher(mockedHasher);
+
+            // WHEN
+            String formatted = converter.convert(createEvent(e));
+
+            // THEN
+            // verify we have the expected stack trace line separator inlined
+            assertThat(formatted).doesNotContain(CoreConstants.LINE_SEPARATOR);
+            assertThat(formatted).contains(ShortenedThrowableConverter.DEFAULT_INLINE_SEPARATOR);
+        }
+    }
+
     @Test
     public void test_inline_hash_with_suppressed() {
         try {