Addressing feedback

Author: jonathan-buttner

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/common/MapPathExtractor.java

@@ -20,7 +20,7 @@
  * Uses a subset of the JSONPath schema to extract fields from a map.
  * For more information <a href="https://en.wikipedia.org/wiki/JSONPath">see here</a>.
  *
- * This implementation differs in out it handles lists in that JSONPath will flatten inner lists. This implementation
+ * This implementation differs in how it handles lists in that JSONPath will flatten inner lists. This implementation
  * preserves inner lists.
  *
  * Examples of the schema:
@@ -133,9 +133,10 @@ public static Object extract(Map<String, Object> data, String path) {
 
         var cleanedPath = path.trim();
 
-        // Remove the prefix if it exists
         if (cleanedPath.startsWith(DOLLAR)) {
             cleanedPath = cleanedPath.substring(DOLLAR.length());
+        } else {
+            throw new IllegalArgumentException(Strings.format("Path [%s] must start with a dollar sign ($)", cleanedPath));
         }
 
         return navigate(data, cleanedPath);

x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/common/MapPathExtractorTests.java

@@ -66,6 +66,11 @@ public void testExtract_ReturnsNull_WhenPathIsWhiteSpace() {
         assertNull(MapPathExtractor.extract(Map.of("key", "value"), "    "));
     }
 
+    public void testExtract_ThrowsException_WhenPathDoesNotStartWithDollarSign() {
+        var exception = expectThrows(IllegalArgumentException.class, () -> MapPathExtractor.extract(Map.of("key", "value"), ".key"));
+        assertThat(exception.getMessage(), is("Path [.key] must start with a dollar sign ($)"));
+    }
+
     public void testExtract_ThrowsException_WhenCannotFindField() {
         Map<String, Object> input = Map.of("result", "key");
 
@@ -76,7 +81,7 @@ public void testExtract_ThrowsException_WhenCannotFindField() {
     public void testExtract_ThrowsAnException_WhenThePathIsInvalid() {
         Map<String, Object> input = Map.of("result", "key");
 
-        var exception = expectThrows(IllegalArgumentException.class, () -> MapPathExtractor.extract(input, "awesome"));
+        var exception = expectThrows(IllegalArgumentException.class, () -> MapPathExtractor.extract(input, "$awesome"));
         assertThat(exception.getMessage(), is("Invalid path received [awesome], unable to extract a field name."));
     }