fix for incorrect parsing of tags as first line of mapping sequence (#6281)

* fix for incorrect parsing of tags as first line of mapping sequence

* Validate the tag is correctly parsed

---------

Co-authored-by: Tim te Beek <tim@moderne.io>

Author: dsgrieve

rewrite-yaml/src/main/java/org/openrewrite/yaml/YamlParser.java

@@ -197,7 +197,7 @@ private Yaml.Documents parseFromInput(Path sourceFile, EncodingDetectingInputStr
                         }
 
                         String fullPrefix = reader.readStringFromBuffer(lastEnd, event.getEndMark().getIndex() - 1);
-                        int startIndex = commentAwareIndexOf(':', fullPrefix) + 1;
+                        int startIndex = commentAwareIndexOf(Arrays.asList(':', '-'), fullPrefix) + 1;
                         Yaml.Tag tag = null;
                         if (mappingStartEvent.getTag() != null) {
                             String prefixAfterColon = fullPrefix.substring(startIndex);

rewrite-yaml/src/test/java/org/openrewrite/yaml/YamlParserTest.java

@@ -466,6 +466,23 @@ void withAnchorSequenceOnRootLevel() {
         );
     }
 
+    @Test
+    void parseTagsCorrectlyOnFirstLineOfMappingEntry() {
+        rewriteRun(
+          yaml(
+            """
+              - !SOMETAG
+                a: b
+              """,
+            spec -> spec.afterRecipe(docs -> {
+                Yaml.Sequence sequence = (Yaml.Sequence) docs.getDocuments().getFirst().getBlock();
+                Yaml.Mapping mapping = (Yaml.Mapping) sequence.getEntries().getFirst().getBlock();
+                assertThat(mapping.getTag().getName()).isEqualTo("SOMETAG");
+            })
+          )
+        );
+    }
+
     @Issue("https://github.com/moderneinc/customer-requests/issues/1471")
     @Test
     void yamlWithDocumentEndMarker() {