[Core] Flush pretty output manually

For the sake of efficiency and performance we write to buffered writers.
However, the pretty plugin is expected to print scenarios as they're started
and steps as they're finished.

This was initially resolved by flushing the `NiceAppendable` on every write.
This turned out to have performance impact (#2481) and interact poorly with
tools that expected (#2536) us to be better behaved.

By having `NiceAppendable` flush only when the underlying buffer was full these
problems were resolved (#2541) . However, because the underlying buffer is 8KiB
the pretty formatters output would effectively sit in a buffer until the writer
was closed.

So now we flush the pretty and progress output manually after each event. This
strikes a balance somewhere between the flush-everything-all-the-time and
flush-when-full approaches.

Fixes: #2563

CHANGELOG.md

@@ -11,13 +11,15 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 * [Core] Warn when glue path is passed as file scheme instead of classpath ([#2547](https://github.com/cucumber/cucumber-jvm/pull/2547) M.P. Korstanje)
 
 ### Changed
+* [Core] Flush pretty output manually ([#2573](https://github.com/cucumber/cucumber-jvm/pull/2573) M.P. Korstanje)
 
 ### Deprecated
 
 ### Removed
 
 ### Fixed
-* [Spring] Cleanly stop after failure to start application context
+* [Spring] Cleanly stop after failure to start application context ([#2570](https://github.com/cucumber/cucumber-jvm/pull/2570) M.P. Korstanje) 
+* [JUnit] Scenario logging does not show up in step notifications ([#2563](https://github.com/cucumber/cucumber-jvm/pull/2545) M.P. Korstanje)
 
 ## [7.3.4] (2022-05-02)
 

core/src/main/java/io/cucumber/core/plugin/AnsiEscapes.java

@@ -30,10 +30,6 @@ static AnsiEscapes up(int count) {
         return new AnsiEscapes(count + "A");
     }
 
-    void appendTo(NiceAppendable a) {
-        a.append(ESC).append(BRACKET).append(value);
-    }
-
     @Override
     public String toString() {
         StringBuilder sb = new StringBuilder();

core/src/main/java/io/cucumber/core/plugin/MessageFormatter.java

@@ -25,7 +25,6 @@ private void writeMessage(Envelope envelope) {
         try {
             Jackson.OBJECT_MAPPER.writeValue(writer, envelope);
             writer.write("\n");
-            writer.flush();
             if (envelope.getTestRunFinished().isPresent()) {
                 writer.close();
             }

core/src/main/java/io/cucumber/core/plugin/PrettyFormatter.java

@@ -22,6 +22,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.io.PrintWriter;
 import java.io.StringReader;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -37,6 +38,12 @@
 import static java.lang.Math.max;
 import static java.util.Locale.ROOT;
 
+/**
+ * Prints a pretty report of the scenario execution as it happens.
+ * <p>
+ * When scenarios are executed concurrently the output will interleave. This is
+ * to be expected.
+ */
 public final class PrettyFormatter implements ConcurrentEventListener, ColorAware {
 
     private static final String SCENARIO_INDENT = "";
@@ -45,11 +52,11 @@ public final class PrettyFormatter implements ConcurrentEventListener, ColorAwar
 
     private final Map<UUID, Integer> commentStartIndex = new HashMap<>();
 
-    private final NiceAppendable out;
+    private final PrintWriter out;
     private Formats formats = ansi();
 
     public PrettyFormatter(OutputStream out) {
-        this.out = new NiceAppendable(new UTF8OutputStreamWriter(out));
+        this.out = new UTF8PrintWriter(out);
     }
 
     @Override
@@ -66,25 +73,27 @@ private void handleTestCaseStarted(TestCaseStarted event) {
         preCalculateLocationIndent(event);
         printTags(event);
         printScenarioDefinition(event);
+        out.flush();
     }
 
     private void handleTestStepFinished(TestStepFinished event) {
         printStep(event);
         printError(event);
+        out.flush();
     }
 
     private void handleWrite(WriteEvent event) {
         out.println();
         printText(event);
         out.println();
-
+        out.flush();
     }
 
     private void handleEmbed(EmbedEvent event) {
         out.println();
         printEmbedding(event);
         out.println();
-
+        out.flush();
     }
 
     private void handleTestRunFinished(TestRunFinished event) {
@@ -188,9 +197,8 @@ private void printText(WriteEvent event) {
             while ((line = lines.readLine()) != null) {
                 builder.append(STEP_SCENARIO_INDENT)
                         .append(line)
-                        .append(System.lineSeparator()); // Add system line
-                                                         // separator - \n won't
-                                                         // do it!
+                        // Add system line separator - \n won't do it!
+                        .append(System.lineSeparator());
             }
         } catch (IOException e) {
             throw new CucumberException(e);

core/src/main/java/io/cucumber/core/plugin/ProgressFormatter.java

@@ -9,6 +9,7 @@
 import io.cucumber.plugin.event.TestStepFinished;
 
 import java.io.OutputStream;
+import java.io.PrintWriter;
 import java.util.HashMap;
 import java.util.Map;
 
@@ -35,13 +36,11 @@ public final class ProgressFormatter implements ConcurrentEventListener, ColorAw
         }
     };
 
-    private final NiceAppendable out;
+    private final PrintWriter out;
     private boolean monochrome = false;
 
     public ProgressFormatter(OutputStream out) {
-        // Configure the NiceAppendable to flush on every append, since the
-        // point of this formatter is to display a progress bar.
-        this.out = new NiceAppendable(new UTF8OutputStreamWriter(out), true);
+        this.out = new UTF8PrintWriter(out);
     }
 
     @Override
@@ -71,6 +70,7 @@ private void handleTestStepFinished(TestStepFinished event) {
             AnsiEscapes.RESET.appendTo(buffer);
         }
         out.append(buffer);
+        out.flush();
     }
 
     private void handleTestRunFinished(TestRunFinished testRunFinished) {

core/src/main/java/io/cucumber/core/plugin/RerunFormatter.java

@@ -8,6 +8,7 @@
 import io.cucumber.plugin.event.TestRunFinished;
 
 import java.io.OutputStream;
+import java.io.PrintWriter;
 import java.net.URI;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -16,18 +17,19 @@
 
 import static io.cucumber.core.feature.FeatureWithLines.create;
 import static io.cucumber.core.plugin.PrettyFormatter.relativize;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
 /**
  * Formatter for reporting all failed test cases and print their locations
  * Failed means: results that make the exit code non-zero.
  */
 public final class RerunFormatter implements ConcurrentEventListener {
 
-    private final NiceAppendable out;
+    private final PrintWriter out;
     private final Map<URI, Collection<Integer>> featureAndFailedLinesMapping = new HashMap<>();
 
     public RerunFormatter(OutputStream out) {
-        this.out = new NiceAppendable(new UTF8OutputStreamWriter(out));
+        this.out = new PrintWriter(out, false, UTF_8);
     }
 
     @Override

core/src/main/java/io/cucumber/core/plugin/UTF8PrintWriter.java

@@ -0,0 +1,13 @@
+package io.cucumber.core.plugin;
+
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.nio.charset.StandardCharsets;
+
+final class UTF8PrintWriter extends PrintWriter {
+
+    UTF8PrintWriter(OutputStream out) {
+        super(out, false, StandardCharsets.UTF_8);
+    }
+
+}

core/src/main/java/io/cucumber/core/plugin/UnusedStepsSummaryPrinter.java

@@ -9,6 +9,7 @@
 import io.cucumber.plugin.event.TestStepFinished;
 
 import java.io.OutputStream;
+import java.io.PrintWriter;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Set;
@@ -23,11 +24,11 @@ public final class UnusedStepsSummaryPrinter implements ColorAware, ConcurrentEv
 
     private final Map<String, String> registeredSteps = new TreeMap<>();
     private final Set<String> usedSteps = new TreeSet<>();
-    private final NiceAppendable out;
+    private final PrintWriter out;
     private Formats formats = ansi();
 
     public UnusedStepsSummaryPrinter(OutputStream out) {
-        this.out = new NiceAppendable(new UTF8OutputStreamWriter(out));
+        this.out = new UTF8PrintWriter(out);
     }
 
     @Override