From 2d775fd3bc35b8d8ef5b6663eff5ea2289f8d5ef Mon Sep 17 00:00:00 2001
From: Alan Woodward <romseygeek@apache.org>
Date: Mon, 10 Jan 2022 11:33:59 +0000
Subject: [PATCH 1/2] Move ambiguous object path detection into
 DotExpandingXContentParser

---
 .../xcontent/DotExpandingXContentParser.java  | 27 ++++++++++++++++++-
 .../index/mapper/DocumentParser.java          |  2 --
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java b/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java
index 704edfd019c9a..670240f594488 100644
--- a/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java
+++ b/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java
@@ -48,7 +48,7 @@ public Token nextToken() throws IOException {
 
         private void expandDots() throws IOException {
             String field = delegate().currentName();
-            String[] subpaths = field.split("\\.");
+            String[] subpaths = splitAndValidatePath(field);
             if (subpaths.length == 0) {
                 throw new IllegalArgumentException("field name cannot contain only dots: [" + field + "]");
             }
@@ -71,6 +71,31 @@ protected XContentParser delegate() {
         }
     }
 
+    private static String[] splitAndValidatePath(String fullFieldPath) {
+        if (fullFieldPath.isEmpty()) {
+            throw new IllegalArgumentException("field name cannot be an empty string");
+        }
+        if (fullFieldPath.contains(".") == false) {
+            return new String[]{fullFieldPath};
+        }
+        String[] parts = fullFieldPath.split("\\.");
+        if (parts.length == 0) {
+            throw new IllegalArgumentException("field name cannot contain only dots");
+        }
+        for (String part : parts) {
+            // check if the field name contains only whitespace
+            if (part.isEmpty()) {
+                throw new IllegalArgumentException("object field cannot contain only whitespace: ['" + fullFieldPath + "']");
+            }
+            if (part.isBlank()) {
+                throw new IllegalArgumentException(
+                    "object field starting or ending with a [.] makes object resolution ambiguous: [" + fullFieldPath + "]"
+                );
+            }
+        }
+        return parts;
+    }
+
     /**
      * Wraps an XContentParser such that it re-interprets dots in field names as an object structure
      * @param in    the parser to wrap
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/DocumentParser.java b/server/src/main/java/org/elasticsearch/index/mapper/DocumentParser.java
index 59baf29a5c531..d5beeba0d82fa 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/DocumentParser.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/DocumentParser.java
@@ -461,7 +461,6 @@ private static void innerParseObject(DocumentParserContext context, ObjectMapper
         while (token != XContentParser.Token.END_OBJECT) {
             if (token == XContentParser.Token.FIELD_NAME) {
                 currentFieldName = context.parser().currentName();
-                splitAndValidatePath(currentFieldName);
             } else if (token == XContentParser.Token.START_OBJECT) {
                 parseObject(context, mapper, currentFieldName);
             } else if (token == XContentParser.Token.START_ARRAY) {
@@ -649,7 +648,6 @@ private static void parseNonDynamicArray(
     ) throws IOException {
         XContentParser parser = context.parser();
         XContentParser.Token token;
-        splitAndValidatePath(lastFieldName);
         while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
             if (token == XContentParser.Token.START_OBJECT) {
                 parseObject(context, mapper, lastFieldName);

From 82ef34c61bbc8ce258d6ddc958365ef7712def4d Mon Sep 17 00:00:00 2001
From: Alan Woodward <romseygeek@apache.org>
Date: Mon, 10 Jan 2022 11:41:22 +0000
Subject: [PATCH 2/2] precommit

---
 .../org/elasticsearch/xcontent/DotExpandingXContentParser.java  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java b/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java
index 670240f594488..d0318b49b62bc 100644
--- a/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java
+++ b/libs/x-content/src/main/java/org/elasticsearch/xcontent/DotExpandingXContentParser.java
@@ -76,7 +76,7 @@ private static String[] splitAndValidatePath(String fullFieldPath) {
             throw new IllegalArgumentException("field name cannot be an empty string");
         }
         if (fullFieldPath.contains(".") == false) {
-            return new String[]{fullFieldPath};
+            return new String[] { fullFieldPath };
         }
         String[] parts = fullFieldPath.split("\\.");
         if (parts.length == 0) {