Apply PR suggestions round 3

Author: mtoffl01

internal-api/src/main/java/datadog/trace/bootstrap/config/provider/StableConfigParser.java

@@ -31,37 +31,35 @@ public static StableConfigSource.StableConfig parse(String filePath) throws IOEx
     Map<String, String> configMap = new HashMap<>();
     String[] configId = new String[1];
     try (Stream<String> lines = Files.lines(Paths.get(filePath))) {
-      // Use AtomicBoolean because it's mutable within a lambda expression to
-      boolean[] apmConfigFound =
-          new boolean[1]; // Track if we've found 'apm_configuration_default:'
-      boolean[] configIdFound = new boolean[1]; // Track if we've found 'config_id:'
+      int apmConfigNotFound = -1, apmConfigStarted = 0, apmConfigComplete = 1;
+      int[] apmConfigFound = {apmConfigNotFound};
       lines.forEach(
           line -> {
             Matcher matcher = idPattern.matcher(line);
             if (matcher.find()) {
               // Do not allow duplicate config_id keys
-              if (configIdFound[0]) {
+              if (configId[0] != null) {
                 throw new RuntimeException("Duplicate config_id keys found; file may be malformed");
               }
               configId[0] = trimQuotes(matcher.group(1).trim());
-              configIdFound[0] = true;
               return; // go to next line
             }
-            // TODO: Do not allow duplicate apm_configuration_default keys? Or just return early.
-            if (!apmConfigFound[0] && apmConfigPattern.matcher(line).matches()) {
-              apmConfigFound[0] = true;
+            // TODO: Do not allow duplicate apm_configuration_default keys; and/or return early once
+            // apmConfigFound[0] == apmConfigComplete
+            if (apmConfigFound[0] == apmConfigNotFound
+                && apmConfigPattern.matcher(line).matches()) {
+              apmConfigFound[0] = apmConfigStarted;
               return; // go to next line
             }
-
-            if (apmConfigFound[0]) {
+            if (apmConfigFound[0] == apmConfigStarted) {
               Matcher keyValueMatcher = keyValPattern.matcher(line);
               if (keyValueMatcher.matches()) {
                 configMap.put(
                     keyValueMatcher.group(1).trim(),
                     trimQuotes(keyValueMatcher.group(2).trim())); // Store key-value pair in map
               } else {
                 // If we encounter a non-indented or non-key-value line, stop processing
-                apmConfigFound[0] = false;
+                apmConfigFound[0] = apmConfigComplete;
               }
             }
           });

internal-api/src/test/groovy/datadog/trace/bootstrap/config/provider/StableConfigParserTest.groovy

@@ -56,4 +56,72 @@ something-else-irrelevant: value-irrelevant
     cfg.get("KEY_FIVE") == "[a,b,c,d]"
     Files.delete(filePath)
   }
+
+  def "test duplicate config_id"() {
+    when:
+    Path filePath = StableConfigSourceTest.tempFile()
+    if (filePath == null) {
+      throw new AssertionError("Failed to create test file")
+    }
+    String yaml = """
+config_id: 12345
+something-irrelevant: ""
+apm_configuration_default:
+  DD_KEY: value
+config_id: 67890
+"""
+
+    try {
+      StableConfigSourceTest.writeFileRaw(filePath, yaml)
+    } catch (IOException e) {
+      throw new AssertionError("Failed to write to file: ${e.message}")
+    }
+
+    Exception exception
+    StableConfigSource.StableConfig cfg
+    try {
+      cfg = StableConfigParser.parse(filePath.toString())
+    } catch (Exception e) {
+      exception = e
+    }
+
+    then:
+    cfg == null
+    exception != null
+    exception.getMessage() == "Duplicate config_id keys found; file may be malformed"
+  }
+
+  def "test duplicate apm_configuration_default"() {
+    // Assert that only the first entry is used
+    when:
+    Path filePath = StableConfigSourceTest.tempFile()
+    if (filePath == null) {
+      throw new AssertionError("Failed to create test file")
+    }
+    String yaml = """
+apm_configuration_default:
+  KEY_1: value_1
+something-else-irrelevant: value-irrelevant
+apm_configuration_default:
+  KEY_2: value_2
+"""
+    try {
+      StableConfigSourceTest.writeFileRaw(filePath, yaml)
+    } catch (IOException e) {
+      throw new AssertionError("Failed to write to file: ${e.message}")
+    }
+
+    StableConfigSource.StableConfig cfg
+    try {
+      cfg = StableConfigParser.parse(filePath.toString())
+    } catch (Exception e) {
+      throw new AssertionError("Failed to parse the file: ${e.message}")
+    }
+
+    then:
+    def keys = cfg.getKeys()
+    keys.size() == 1
+    !keys.contains("KEY_2")
+    cfg.get("KEY_1") == "value_1"
+  }
 }