fix: handling empty yaml config file with a comment only (#3301)

Author: csviri

operator-framework/src/main/java/io/javaoperatorsdk/operator/config/loader/provider/YamlConfigProvider.java

@@ -100,8 +100,16 @@ private static Map<String, Object> load(Path path) {
       return Map.of();
     }
 
-    try (InputStream in = Files.newInputStream(path)) {
-      Map<String, Object> result = MAPPER.readValue(in, Map.class);
+    try (InputStream in = Files.newInputStream(path);
+        com.fasterxml.jackson.core.JsonParser parser = MAPPER.getFactory().createParser(in)) {
+      if (parser.nextToken() == null) {
+        log.debug(
+            "YAML file contains no mappings (possibly empty or comments only). "
+                + "Returning empty config. Path: {}",
+            path);
+        return Map.of();
+      }
+      Map<String, Object> result = MAPPER.readValue(parser, Map.class);
       return result != null ? result : Map.of();
     } catch (IOException e) {
       throw new UncheckedIOException("Failed to load config YAML from " + path, e);

operator-framework/src/test/java/io/javaoperatorsdk/operator/config/loader/provider/YamlConfigProviderTest.java

@@ -16,6 +16,7 @@
 package io.javaoperatorsdk.operator.config.loader.provider;
 
 import java.io.IOException;
+import java.io.UncheckedIOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.time.Duration;
@@ -26,6 +27,7 @@
 import org.junit.jupiter.api.io.TempDir;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
 class YamlConfigProviderTest {
@@ -132,10 +134,60 @@ void loadsFromFile(@TempDir Path dir) throws IOException {
     assertThat(provider.getValue("josdk.test.integer", Integer.class)).hasValue(7);
   }
 
+  @Test
+  void emptyFile(@TempDir Path dir) throws IOException {
+    Path file = dir.resolve("empty.yaml");
+    Files.writeString(file, "");
+
+    var provider = new YamlConfigProvider(file);
+    assertThat(provider.getValue("any.key", String.class)).isEmpty();
+  }
+
+  @Test
+  void fileWithCommentOnly(@TempDir Path dir) throws IOException {
+    Path file = dir.resolve("empty.yaml");
+    Files.writeString(
+        file,
+        """
+        # sample comment
+        """);
+    var provider = new YamlConfigProvider(file);
+    assertThat(provider.getValue("any.key", String.class)).isEmpty();
+  }
+
   @Test
   void returnsEmptyForNonExistingFile(@TempDir Path dir) {
     Path missing = dir.resolve("does-not-exist.yaml");
     var provider = new YamlConfigProvider(missing);
     assertThat(provider.getValue("any.key", String.class)).isEmpty();
   }
+
+  @Test
+  void throwsForMalformedYaml(@TempDir Path dir) throws IOException {
+    Path file = dir.resolve("bad.yaml");
+    // YAML list where a map is expected
+    Files.writeString(
+        file,
+        """
+        - item1
+        - item2
+        """);
+    assertThatExceptionOfType(UncheckedIOException.class)
+        .isThrownBy(() -> new YamlConfigProvider(file));
+  }
+
+  @Test
+  void commentWithProperDocument(@TempDir Path dir) throws IOException {
+    Path file = dir.resolve("filewithcomment.yaml");
+    // YAML comment followed by a proper mapping document
+    Files.writeString(
+        file,
+        """
+        # comment
+        key:
+          subkey: val
+        """);
+    var provider = new YamlConfigProvider(file);
+    assertThat(provider.getValue("key.subkey", String.class)).contains("val");
+  }
 }