Redirect warnings to stderr

Author: filipesperandio

src/OutputParser.groovy

@@ -0,0 +1,28 @@
+
+class OutputParser {
+  public def out
+  public def err
+
+  OutputParser(out, err) {
+    this.out = new OutStreamProcessor(out);
+    this.err = err
+  }
+
+  class OutStreamProcessor extends PrintStream {
+    public OutStreamProcessor(out) {
+      super(out);
+    }
+
+    public void print(String line) {
+      if(isJson(line)) {
+        super.print(line)
+      } else {
+        this.err.print(line)
+      }
+    }
+
+    boolean isJson(txt) {
+      return txt.startsWith("{");
+    }
+  }
+}

src/main.groovy

@@ -2,11 +2,12 @@ import groovy.util.*
 
 class Main {
   static def execute(command) {
+    OutputParser parser = new OutputParser(System.out, System.err)
     ProcessBuilder builder = new ProcessBuilder(command.split(' '))
     def env = builder.environment()
     env.put("JAVA_OPTS", "-XX:MinHeapFreeRatio=10 -XX:MaxHeapFreeRatio=30")
     Process process = builder.start()
-    process.consumeProcessOutput(System.out, System.err)
+    process.consumeProcessOutput(parser.out, parser.err)
     process.waitFor()
     System.exit(process.exitValue())
   }

test/OutputParserTest.groovy

@@ -0,0 +1,34 @@
+import static org.junit.Assert.*
+import org.junit.*
+
+class OutputParserTest {
+  def out
+  def err
+  def parser
+
+  @Before
+  public void setup() {
+    out = new ByteArrayOutputStream()
+    err = new ByteArrayOutputStream()
+
+    def outStream = new PrintStream(out)
+    def errStream = new PrintStream(err)
+
+    parser = new OutputParser(outStream, errStream)
+  }
+
+  @Test
+  public void redirectNonJsonInput() {
+    parser.out.print("This is a warning")
+    assert out.toString("UTF-8").isEmpty()
+    assert "This is a warning", err.toString("UTF-8")
+  }
+
+  @Test
+  public void printJsonLines() {
+    parser.out.print("{}")
+    assert err.toString("UTF-8").isEmpty()
+    assert "{}", out.toString("UTF-8")
+  }
+}
+

test/SanityCheckTest.groovy

@@ -4,15 +4,29 @@ import groovy.util.FileNameFinder
 import static org.junit.Assert.*
 import org.junit.*
 
+class CustomIO {
+  def byteStream
+  def printStream
+
+  CustomIO() {
+    byteStream = new ByteArrayOutputStream()
+    printStream = new PrintStream(byteStream)
+  }
+
+  public String toString() {
+    return byteStream.toString("UTF-8")
+  }
+}
+
 class SanityCheckTest {
   def execute(command) {
     def proc = command.execute()
-    def out = new StringBuffer()
-    def err = new StringBuffer()
+    def outIO = new CustomIO()
+    def errIO = new CustomIO()
 
-    proc.waitForProcessOutput(out, err)
+    proc.waitForProcessOutput(outIO.printStream, errIO.printStream)
 
-    return [proc, out, err]
+    return [proc, outIO, errIO]
   }
 
   @Test