Fix crash-tracking uploader script overwrite warning (#7386)

Author: jbachorik

dd-java-agent/agent-crashtracking/src/main/java/com/datadog/crashtracking/ScriptInitializer.java

@@ -249,21 +249,23 @@ static void initializeOOMENotifier(String onOutOfMemoryVal) throws IOException {
   private static void writeScript(
       InputStream template, Path scriptPath, String execClass, String crashFile)
       throws IOException {
-    try (BufferedReader br = new BufferedReader(new InputStreamReader(template))) {
-      try (BufferedWriter bw = Files.newBufferedWriter(scriptPath)) {
-        br.lines()
-            .map(
-                line -> {
-                  line = Strings.replace(line, "!AGENT_JAR!", execClass);
-                  if (crashFile != null) {
-                    line = Strings.replace(line, "!JAVA_ERROR_FILE!", crashFile);
-                  }
-                  return line;
-                })
-            .forEach(line -> writeLine(bw, line));
+    if (!Files.exists(scriptPath)) {
+      try (BufferedReader br = new BufferedReader(new InputStreamReader(template))) {
+        try (BufferedWriter bw = Files.newBufferedWriter(scriptPath)) {
+          br.lines()
+              .map(
+                  line -> {
+                    line = Strings.replace(line, "!AGENT_JAR!", execClass);
+                    if (crashFile != null) {
+                      line = Strings.replace(line, "!JAVA_ERROR_FILE!", crashFile);
+                    }
+                    return line;
+                  })
+              .forEach(line -> writeLine(bw, line));
+        }
       }
+      Files.setPosixFilePermissions(scriptPath, PosixFilePermissions.fromString("r-xr-xr-x"));
     }
-    Files.setPosixFilePermissions(scriptPath, PosixFilePermissions.fromString("r-xr-xr-x"));
   }
 
   private static void writeLine(BufferedWriter bw, String line) {

dd-java-agent/agent-crashtracking/src/test/java/com/datadog/crashtracking/ScriptInitializerTest.java

@@ -68,6 +68,17 @@ void testCrashUploaderInitializationSuccess(String target, String pidArg)
     assertTrue(lines.stream().anyMatch(l -> l.contains(hsErrFile)));
   }
 
+  @Test
+  void testCrashUploaderInitializationExisting() throws IOException {
+    Path file = tempDir.resolve("dd_crash_uploader.sh");
+    Files.createFile(file);
+    ScriptInitializer.initializeCrashUploader(file.toString(), "/tmp/hs_err%p.log");
+    assertTrue(Files.exists(file), "File " + file + " should not have been removed");
+    assertTrue(
+        Files.readAllLines(file).isEmpty(),
+        "File " + file + " content should not have been modified");
+  }
+
   private static Stream<Arguments> crashTrackingScripts() {
     return Stream.of(
         Arguments.of("dd_crash_uploader.sh", ""),